67 results on '"Tucker MP"'
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2. Methodology characteristics of a 'FM in healthcare' field study on risk management of Legionella in water systems
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Leiblein, T, Tucker, MP, and Hofer, S
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HD ,HD28 - Abstract
The aim of an ongoing research project is to systematically uncover the present situation of legionella prevention in water systems in selected health care (HC) organisations in different countries. It seeks to develop a ‘reference system’ guiding those responsible in HC organisations to identify, understand and properly take action for prevention. By considering stakeholder theory, business research methods, process and quality theory and corresponding definitions, a fundamental reference will be provided for operationalisation and specific analysis. The present paper aims at providing a fundament for the research methodology, which is then applied to the research project. It represents the theoretical foundation of the research project and is the guiding element for aligning activities to work towards the research output at the final stage of the project. The research project is driven by the perspectives of FM / FS and follows an exploratory mixed-methods design including several cases. As a synthesis of the theories and definitions proposed, the procedures for an exploratory instrument design mixed methods study was constructed and are presented. It is only through the empirically justified logic of an appropriate reference system that evidence-providing elements can be identified and described in a comprehensible manner. The reflection of processes, identification of process owners and the optimisation of certain areas which FM and FS serve is becoming more important than ever. With the final result of a framework at the end of the research project, FM and FS people responsible in HC organisations obtain a meaningful instrument. This can be used as a management tool and will be formed with respect to a process-oriented perspective, issuing an organisation’s protection goal of ‘infection prevention’. The framework could help those responsible to reflect on their missions throughout the organisation and adjust (strategic) planning where seen necessary.
3. Recognising the socio-technical opportunity of workplace: an analysis of early responses to COVID-19
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Moriarty, C, Tucker, MP, Ellison, I, Pinder, J, and Wilson, H
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HD28 ,Business - Abstract
COVID-19 has disrupted the ways in which we work, offering an opportunity to rethink our workplaces. Organisations have had to adapt and respond in unprecedented ways to enable continued organisational performance that have come to see many working from home. Early responses to ‘return-to-work’ have sought to repurpose existing workspace arrangements, but they miss the unique opportunity to reconceive ‘workplace’ more comprehensively, as well as the role the property community have in enabling work. This paper aims to highlight the opportunity of viewing workplace holistically through the lens of socio-technical systems. An examination of the early responses to the pandemic identified a focus on the technical aspects of reoccupying workspaces, but taking from socio-technical systems, this should not be at the detriment to other factors. A more nuanced debate regarding who should return to work and how this will occur is presented, which highlights further a need to move beyond the physical workspace and to reflect on how we can enable ways of working.
4. Green buildings and well-being of employees in commercial spaces
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Hartwell, J, Tucker, MP, and Siriwardena, M
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TA ,TH - Abstract
As recently as forty years ago, the Facilities Management profession was relatively unknown in the built environment industry. Buildings were generally maintained serviced and cleaned. The Facilities Management profession is now one of the fastest growing professions in the UK and as a result, there is a growing list of services to provide, including delivering on environmental commitments and sustainable practices. This research adds to the growing body of literature on the profound effects sustainable buildings can have on its occupants and converts these benefits into financial metrics which benefit both landlords and tenants of commercial buildings. Although there is conclusive evidence of the benefits, there is still a perception that building green does not represent value for money. This paper aims to investigate to what extent facilities managers are responsible for introducing sustainable initiatives that enhance the health well-being and productivity of employees. To achieve this aim, primary data was gathered through face to face interviews with Facilities Management professionals. The findings reveal that although sustainability was viewed as important and is highly valued by most organisations, there are more important priorities to focus on. The results from the interviews found that 100% percent of the organisations who participated had sustainability policies in place and the main drivers for introducing those policies was to comply with legislation and to provide a healthier, more attractive workplace for their employees. Although sustainability and the health, well-being and productivity of employees was a main driver, as well as being embraced and promoted by Facilities Managers, ultimately, they felt that they had more important responsibilities to focus on, hence it did not feature as a priority in their day to day job. This was also identified as one of the main barriers for sustainable Facilities Management to improve, as well as cost, the current skillset and knowledge of Facilities Managers.
5. The maturity of Facility Management in South East Europe
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Tucker, MP, Temeljotov-Salaj, A, Tangerås, M, and Tucker, M
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HD28 ,Business - Abstract
Purpose: In Europe, facilities management (FM) is generally seen as a mature market. However, this is largely the case because of the high level of sophistication of the FM market in central and northern Europe. South East Europe (SEE) however, is less developed and lacks the maturity of many of its European neighbours. To date, little research has been undertaken to really establish why this is the case, and why there are disparities with other parts of Europe. This study aims to gain a qualitative understanding of the complexities of developing a mature FM market across SEE. Methodology: The purpose of the research is to take an inductive, constructivist approach to gaining knowledge about the maturity of the FM market in SEE. This is because, to date, there is no data that has investigated the state of FM from a qualitative perspective. There is only currently general statistics available to investigate this issue. Data is collected through in-depth, semi-structured interviews. The findings will critically analyse the perceptions of each country located in SEE, regarding their key challenges and opportunities of the business environment; FM organizations; FM supply market; Professional bodies; FM education; and FM research. The interviews enable the critical evaluation of the maturity of the FM market in SEE. Findings: The qualitative findings provide an alternative perspective to previous studies that look at the FM market in Europe. The findings show that the FM market is very competitive in this region, but at the same time, the market is still undeveloped in some of the countries. The most recognisable and mature FM business is in Bulgaria, in which the maturity of all measured segments were highest. Impact: FM is a global discipline, recognised in every sector, in every organisation. At a global level, this is a very pertinent topic, as FM is increasingly being standardised and globalised through the generation of a new suite of ISO standards (ISO41000 series), the first of its kind for FM. However, across the globe, especially in Europe, there are varying degrees of maturity of the discipline.
6. Implications for the Standardisation of Facilities Management
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Tucker, MP and Cannon, T
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HD28 ,Business
7. Sustainable Facilities Management
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Tucker, MP, Cotgrave, A, and Riley, M
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HD ,HD61 ,HD28 ,Business - Abstract
Book chapter
8. Synergy of FM competences
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Tucker, MP and Roper, K
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HD28 ,TH - Abstract
Purpose Based on a content analysis of facility management (FM) competencies from three key professional associations, BIFM, IFMA and RICS, the resulting identified competencies for effective FM were found to be somewhat diverse based on association affiliation. However, the majority of emphasis clustered around five competencies that all groups coalesced around, demonstrating the strength of these shared competencies as core for FM.\ud Findings, Key among the findings was that the top five competencies included: Compliance & standards; Contracts & procurement; Maintenance & operations; Sustainability; and Projects. Further analysis showed that each association had unique approaches in specialized areas inherent to that association’s purpose and history. There were also striking omissions on several competencies which point to a need for further discussion on whether to update/add competencies to align with other professional associations. What was clear was the balance of mentioned competencies within the full range of competencies for all three associations. It was an unexpected result which merits attention, especially in light of global standardization initiatives.\ud Design/methodology/approach A complete review of the methodology, analysis and findings is included in this paper, providing the ability for future research to develop standardization worldwide. With the current ISO standard for Facility Management (FM) undergoing task group development, these research findings are essential for addressing industry needs in a robust, academic way.\ud Originality/value.Discussion of the results across the broad spectrum of facility management researchers involved in EuroFM is needed to enhance standards development and advance the research agenda for academic facility management education.
9. Employer’s Information Requirements (EIR): A BIM case study to meet client and facility manager needs
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Ashworth, S, Tucker, MP, and Druhmann, C
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HD ,HD28 - Abstract
Purpose: This paper describes the development, testing and case study use of an Employer’s Information Requirements (EIR) Template and Guidance document designed to meet client and facility management (FM) needs in the Building Information Modelling (BIM) process.\ud Theory: UK BIM standards and EIR examples formed a basis for drafting the EIR.\ud Design/methodology/approach: Triangulation using:1) a review of literature and BIM standards, 2) a focus-group; with the British Institute of Facilities Management (BIFM), 3) a case study interviews; with the Glasgow Life Burrell Renaissance Project who trialled the EIR, and 4) peerreviews and interviews with BIM/CAFM experts from BIM Academy1 and FM1802.\ud Findings: There is need for FM and client specific guidance including how to prepare an EIR. Practitioners are aware of key BIM standards but not in detail. The case study EIR was used by clients, FMs and the design team as a collaboration-tool to bring stakeholders together to discuss and understand the client’s information needs.\ud Originality/value: The full version of EIR Template and Guidance document is available at http://www.bifm.org.uk/bifm/knowledge. It provides a practical starting-point for capturing client information requirements in a structured way. It provides design/construction professionals with clear client instructions allowing a well aligned BIM Execution Plan (BEP) in their tender response. This will in turn ensure the BIM process delivers the right information for optimising asset usability and costs over the long term in operation.
10. Unravelling the variables to calculate an organisations return on workplace investment: a scoping review process
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Tucker, MP, Wilson, HK, Oseland, Nigel, Brogan, Peter, and Horsley, Annie
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HD28 ,Business - Abstract
Purpose: to present the initial findings of the first phase of a research project being conducted in partnership with the Institute of Workplace and Facilities Management (IWFM) to eventually develop a user-friendly ‘tool’ to calculate the return on workplace investment. The first phase of the project explores the variables that should be measured to eventually incorporate in to the ‘tool’ in order to calculate the return on workplace investment.\ud Theory: the paper looks through the theoretical lens of ‘workplace’ by view the interaction and interconnection between the ‘physical space’, ‘digital space’ and ‘people’ for the overarching purpose of work activity.\ud Design/methodology/approach: a scoping review was conducted by adapting the framework used by Arksey and O'Malley (2005). A total of 70 sources were eventually found, consisting of peerreviewed journal papers, industry reports and other research documents.\ud Findings: the sources were thematically analysed using an inductive thematic analysis approach. A total of six ‘high level’ themes were uncovered, to which a total of 37 ‘lower level’ themes were established.\ud Originality/value: Currently there is no holistic tool to assist workplace professionals in making major decisions regarding changes to their workplace environment. This project aims to bridge this gap by developing a user-friendly tool to calculate the potential return on workplace investment.
11. The Role of FM in Preparing a BIM Strategy and Employer’s Information Requirements (EIR) to Align with Client Asset Management Strategy
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Ashworth, S, Tucker, MP, and Druhmann, C
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HD28 - Abstract
Purpose: To investigate the role of Facility Management (FM) in developing client strategy for Building Information Management (BIM) and Employer’s Information Requirements (EIR) in order to define what information is needed, in which format and when in the BIM process.\ud Design methodology/approach: BIM/FM related scientific literature and UK standards/guidelines were reviewed to establish key documents/terminology facility managers (FMs) should be familiar with when engaging in a BIM project. A workshop questionnaire assessed UK FMs level of understanding of BIM documents/terminology. An FM-BIM Strategy Concept Model was subsequently developed to summarise the role of FM in the BIM process.\ud Originality: The research address a significant research gap regarding the FM role in developing a BIM-strategy/EIR at the start of the BIM process aligned with the client’s Asset Management (AM) strategy. The concept model outlines the process for co-creation with clients and other whole life stakeholders to prepare a BIM strategy/EIR based on a solid understanding of BIM standards, guidelines and tools. The FM-BIM Strategy Concept Model is based on UK standards. However the general principles could be applied to any country with a similar whole life cycle design, build and operate processes and standards.\ud Findings: Most FMs have heard about BIM but few have a deep understanding or practical experience. Guidance is needed focusing specifically on what FMs need to know when developing the client BIM strategy/EIR. These documents can then be used to brief stakeholders in the creation of assets to ensure the right information is handed across for operation.
12. Minutes of FM Meetings in Swiss Hospitals – Worth a Look at
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Honegger, F, Tucker, MP, and Hofer, S
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HD28 - Abstract
Purpose: Effective communication is a prerequisite for a well-functioning Facility Management (FM) in any organisation. As part of formal communication structures, meetings are a powerful tool at the disposal of Facility Managers. Minute-taking is predominantly done in formal meetings and performs four essential functions: constitutional, historical, executive and progressive. This research looks at the structure and content of minutes taken in FM meetings in Swiss general hospitals. The aim is to provide a guideline for managers to analyse and, if applicable, improve meeting minutes and hence meetings they are responsible for.\ud Methodology: The research is based on a case study design. Data collection methods include document research. A total of 402 sets of minutes of FM department and division meetings amounting to 1420 pages have been analysed applying qualitative coding procedures.\ud Key findings: Even though the formal structure of the meetings is similar, the spectrum of their content varies. Predominantly the content provides passive information with little evidence that the meeting is used as a platform to piece together the knowledge and experience of several people advancing FM.\ud Intended impact of the study: Within FM and especially within the context of FM in hospitals meetings have not been looked at using the suggested methodology. It provides a unique insight on what minutes as historical evidence reveal of the meetings’ purpose and provides food for thoughts for executives being responsible of meeting structure and content. The findings of this applied research and the method leading to them provide a guideline for FM executives, to analyse and, if applicable, to improve minute-taking practices and, critically, to improve their meetings. For instance, results indicating a predominant exchange of information among meeting participants whose areas of responsibilities due to the nature of FM have not so much common can lead to dissatisfaction of participants, as a large amount of meeting time is not directly addressed to their needs. Considering this, the findings enable to manage expectations, as knowing and if applicable proactively declaring that the purpose of the meeting is information exchange makes that procedure more tolerable for participants. Because in times of a tightening financial environment within the healthcare context, available resources such as meeting time must be used to their full extent.
13. The role and effectiveness of a formal sustainability policy in Facilities Management
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Price, S, Pitt, M, Marmot, A, Tucker, MP, Mclennan, P, and Ucci, M
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HD ,HD28 - Abstract
The paper develops the level of understanding of the current position of FM providers surrounding sustainable FM. The research establishes, through looking at a sample of FM companies, the level of commitment the FM industry is dedicating to the sustainability movement through looking at the sustainable business practice which stems from their Sustainability Policy (SP).\ud A data analysis of 65 FM companies was carried out. The companies were all members of the BIFM and were a mix of small, medium and large companies (according to employee number) as well as a mix of FM only organisations or FM+ (an FM branch of a construction firm for example). The data analysis looked at each company’s commitment to sustainable business practice and the affect organisational characteristics had on this. This was achieved by creating a predetermined list of self questions to complete for each company; covering organisational characteristics and indicators to sustainable practice.\ud The research found that companies which have a sustainability policy are more likely to implement sustainable business practice, resulting in gaining awards, reporting on sustainable issues and setting targets. Many companies that do not have a policy still participate in these areas but less effectively. Company size also has a significant effect on sustainable business practice, with large companies much more likely to behave in a sustainable way.\ud This paper does not look at the reasons for not having a sustainability policy or practising sustainable business management. The paper demonstrates the purpose and effectiveness of a formal Facilities Management sustainability policy. As such the paper is useful in the preparation of a sustainability strategy.
14. Introduction of employer information requirements (EIR ) template and guidance for Facility Management
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Tucker, MP and Ashworth, S
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HD28 ,TH
15. The Engineering Council’s influence on Building Services Engineering education and qualifications: towards an internationalist education and training model
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King, DC, Tucker, MP, and Cotgrave, A
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TA ,LC ,TH ,TA Engineering (General). Civil engineering (General) ,TH Building construction ,L1 ,LC Special aspects of education ,L Education (General) - Abstract
A large number of Building Services Engineering (BSE) graduates from UK universities either already live and work abroad, or aspire to do so, and the destinations for such migrants are most often English-speaking countries or countries where English is commonly used in business. Academic programmes in BSE are usually professionally accredited by the Chartered Institution of Building Services Engineers (CIBSE) under licence from the Engineering Council (EC). In the common destination countries for UK BSE graduates the Washington, Sydney and Dublin Accord (WSDA) agreements prevail, meaning that there is a mutual recognition of engineering qualifications and professional accreditation of academic courses, and this facilitates international mobility. Since it is widely accepted that buildings account for as much as 50% of greenhouse gas emissions worldwide, it could be said that there is a worldwide sustainability agenda with respect to buildings. The common factor across national boundaries is that Building Services Engineers, as central members of building design teams, must provide much of the specialist practical knowledge to enable more energy efficient buildings to be designed and constructed, and it is therefore likely that UK educated engineers will be working in far more varied overseas locations in the near future. The main aim of the work is to synthesise an education and training model to encourage and enable international mobility of UK BSE graduates, and to carry out some evaluation of this model. This work sets out initially to question whether a UK education in BSE necessarily provides UK graduates with the best possible skillset for work abroad. The influence of the EC upon the content of BSE study programmes has been examined, and the research assesses the benefits of the EC’s influence in countries with different economic and political priorities to the UK, other western economies and to the WSDA countries. Following identification and analysis of the main issues, the model was constructed and evaluations were made using semi-structured interviews. The methodology used in this research is necessarily underpinned by a pragmatist paradigm, which has led to the use of a mixed methods blended approach. In addition to thorough review and analysis of literature, the practical methods employed include a questionnaire survey and semi-structured interviews in three phases: an exploratory phase, an in-depth analysis, and a concluding phase. The early conclusions indicated that the EC influence upon BSE study programmes is generally regarded as necessary and beneficial, since it provides an engineering skillset that is internationally respected and recognised. There is, however, less confidence in applying this in an international arena outside of the WSDA umbrella since different parts of the world face different economic challenges, divergent societal imperatives, and diverse attitudes to sustainability and green issues. An education and training model was constructed to address these issues and, after initial testing, was found generally to be a workable proposition to enhance the international prospects of UK BSEs, and further, could be adopted in the UK under the auspices of the Degree Apprenticeship initiatives. Such a model is, however, unlikely to be adopted in many overseas locations due to differing cultural views on the value of work-based learning and apprenticeship.
16. OPTIMISING FACILITY MANAGEMENT (FM) COMMUNICATION IN SWISS HOSPITALS: THE DEVELOPMENT OF A FM COMMUNICATION FRAMEWORK
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Honegger, F and Tucker, MP
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HE ,HD28 ,Business - Abstract
The thesis combines and contributes literature on healthcare, facility management (FM) com-prising the non-medical processes in hospitals, organisational theory and organisational com-munication in light of FM communication in hospitals. It addresses the research gap of non-existing evidence-based research focusing on FM communication in Swiss hospitals for the benefit of FM executives. This is a gap because well-defined organisational communication is a prerequisite for any organisation to function. Nested within business and management research, a mixed-method case study research de-sign was applied, following a primarily inductive approach led by pragmatism. A series of in-terviews with, and a survey addressed to, FM executives with an analysis of FM meeting minutes established characteristics and challenges of formal and informal communication ac-tivities within the context of hospitals’ FM departments. Results show that traditional channels such as e-mail, phone and scheduled meetings domi-nate. Digitalisation is still in its early stages. Meetings and e-mail communication consume substantial resources while there is a risk that these are not used effectively and efficiently. The majority of hospitals’ FM departments do not have specific and consciously aligned com-munication guidelines available. Meeting minutes revealed that the “FM diversity”, by providing a variety of support processes managed by staff with different professional backgrounds and expert knowledge, is not thoroughly used as an asset to collaboratively achieve tasks together. The research implication is a framework optimising communication procedures in Swiss hos-pitals’ FM departments. The framework supports FM executives to check and if necessary, adjust communication procedures within their respective areas of responsibility. The frame-work consists of 10 key elements supporting effective and efficient FM communication. They are put together in a stand-alone 7-page readily understood document. It includes 27 self-check questions raising FM executives’ awareness regarding these elements as a basis to optimise communication activities in their areas of responsibility. The thesis contributes to op-timising FM communication in Swiss hospitals and to knowledge by taking into account the communication requirements within this particular context. Research limitations include that the implications are subject of the particular context of Swiss hospitals’ FM departments. Further does the framework not provide a specific recipe to ensure effective and efficient FM communication. It raises awareness for FM executives to develop communication procedures tailored to their respective areas of responsibility. Nevertheless, the framework does provide a first step as a basis for future research opportunities considering more detailed the “recipe” aspect desired by FM executives.
17. Iron incorporation both intra- and extra-cellularly improves the yield and saccharification of switchgrass (Panicum virgatum L.) biomass.
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Lin CY, Donohoe BS, Bomble YJ, Yang H, Yunes M, Sarai NS, Shollenberger T, Decker SR, Chen X, McCann MC, Tucker MP, Wei H, and Himmel ME
- Abstract
Background: Pretreatments are commonly used to facilitate the deconstruction of lignocellulosic biomass to its component sugars and aromatics. Previously, we showed that iron ions can be used as co-catalysts to reduce the severity of dilute acid pretreatment of biomass. Transgenic iron-accumulating Arabidopsis and rice plants exhibited higher iron content in grains, increased biomass yield, and importantly, enhanced sugar release from the biomass., Results: In this study, we used intracellular ferritin (FerIN) alone and in combination with an improved version of cell wall-bound carbohydrate-binding module fused iron-binding peptide (IBPex) specifically targeting switchgrass, a bioenergy crop species. The FerIN switchgrass improved by 15% in height and 65% in yield, whereas the FerIN/IBPex transgenics showed enhancement up to 30% in height and 115% in yield. The FerIN and FerIN/IBPex switchgrass had 27% and 51% higher in planta iron accumulation than the empty vector (EV) control, respectively, under normal growth conditions. Improved pretreatability was observed in FerIN switchgrass (~ 14% more glucose release than the EV), and the FerIN/IBPex plants showed further enhancement in glucose release up to 24%., Conclusions: We conclude that this iron-accumulating strategy can be transferred from model plants and applied to bioenergy crops, such as switchgrass. The intra- and extra-cellular iron incorporation approach improves biomass pretreatability and digestibility, providing upgraded feedstocks for the production of biofuels and bioproducts.
- Published
- 2021
- Full Text
- View/download PDF
18. Ferrous and Ferric Ion-Facilitated Dilute Acid Pretreatment of Lignocellulosic Biomass under Anaerobic or Aerobic Conditions: Observations of Fe Valence Interchange and the Role of Fenton Reaction.
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Wei H, Wang W, Ciesielski PN, Donohoe BS, Zhang M, Himmel ME, Chen X, and Tucker MP
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- Aerobiosis, Anaerobiosis, Catalysis, Hydrogen Peroxide chemistry, Hydrolysis, Iron, Oxidation-Reduction, Oxygen, Biomass, Ferric Compounds chemistry, Ferrous Compounds chemistry, Lignin chemistry
- Abstract
Ferrous ion co-catalyst enhancement of dilute-acid (DA) pretreatment of biomass is a promising technology for increasing the release of sugars from recalcitrant lignocellulosic biomass. However, due to the reductive status of ferrous ion and its susceptibility to oxidation with exposure to atmosphere, its effective application presumably requires anaerobic aqueous conditions created by nitrogen gas-purging, which adds extra costs. The objective of this study was to assess the effectiveness of oxidative iron ion, (i.e., ferric ion) as a co-catalyst in DA pretreatment of biomass, using an anaerobic chamber to strictly control exposure to oxygen during setup and post-pretreatment analyses. Remarkably, the ferric ions were found to be as efficient as ferrous ions in enhancing sugar release during DA pretreatment of biomass, which may be attributed to the observation that a major portion of the initial ferric ions were converted to ferrous during pretreatment. Furthermore, the detection of hydrogen peroxide in the liquors after DA/Fe ion pretreatment suggests that Fenton reaction chemistry was likely involved in DA/Fe ion pretreatments of biomass, contributing to the observed ferric and ferrous interchanges during pretreatment. These results help define the extent and specification requirements for applying iron ions as co-catalysts in DA pretreatments of biomass.
- Published
- 2020
- Full Text
- View/download PDF
19. An Improved Leaf Protoplast System for Highly Efficient Transient Expression in Switchgrass (Panicum virgatum L.).
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Lin CY, Wei H, Donohoe BS, Tucker MP, and Himmel ME
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- Panicum growth & development, Plants, Genetically Modified, Plasmids genetics, Seedlings growth & development, Seeds growth & development, Sterilization, Transfection, Ultracentrifugation, Gene Expression, Panicum genetics, Plant Leaves metabolism, Protoplasts metabolism
- Abstract
As a robust perennial C4-type monocot plant and a native species to North America, switchgrass (Panicum virgatum) has been evaluated and designated as a strong candidate bioenergy crop by the U.S. DOE. Although genetic modifications of switchgrass have been used to successfully reduce the recalcitrance of switchgrass biomass for biofuel production, the generation of transgenic switchgrass is still a slow and laborious process. A transient protoplast system can provide an excellent platform to accelerate the selection of genes-of-interest for tailoring switchgrass biomass. However, partially due to the lack of the complete genomic information, the attempts to optimize the transient protoplast system for switchgrass remain scarce. In this chapter, we provide an improved protocol for switchgrass protoplast isolation, increased transformation efficiency using CsCl gradient ultracentrifugation-derived plasmid DNA and extended application of the transient switchgrass protoplast system to analyze protein expression using western blot.
- Published
- 2020
- Full Text
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20. Simultaneous upgrading of biomass-derived sugars to HMF/furfural via enzymatically isomerized ketose intermediates.
- Author
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Wang W, Mittal A, Pilath H, Chen X, Tucker MP, and Johnson DK
- Abstract
Background: Recently, exploring fermentative or chemical pathways that convert biomass-derived sugars to fuels/chemicals has attracted a lot of interest from many researchers. We are investigating a hydrocarbon pathway from mixed sugars via 5-hydroxymethyl furfural (HMF) and furfural intermediates. To achieve this goal, we must first convert glucose and xylose to HMF and furfural in favorable yields. Current processes to produce HMF/furfural generally involve the use of acid catalysts in biphasic systems or solvents such as ionic liquids. However, the yield from transforming glucose to HMF is lower than the yield of furfural from xylose., Results: In this study, we present an efficient chemical pathway simultaneously transforming glucose and xylose to HMF and furfural via ketose intermediates, i.e., fructose and xylulose, which were generated from glucose and xylose via enzymatic isomerization. In the enzymatic isomerization, by adding sodium borate to complex with the ketoses, xylose conversion reached equilibrium after 2 h with a conversion of 91% and glucose conversion reached 84% after 4 h. By enzymatically isomerizing the aldoses to ketoses, the following dehydration reactions to HMF and furfural could be performed at low process temperatures (i.e., 110-120 °C) minimizing the side reactions of the sugars and limiting the degradation of furfurals to humins and carboxylic acids. At 120 °C, pH 0.5, and 15 min reaction time, mixed ketose sugars were converted to HMF and furfural in yields of 77% and 96%, respectively (based on starting aldose concentrations)., Conclusion: Taken together, our results demonstrate that this combined biological and chemical process could be an effective pathway to simultaneously convert biomass-derived glucose and xylose to HMF and furfural, for use as intermediates in the production of hydrocarbons., Competing Interests: Competing interestsThe authors declare that they have no competing interests., (© The Author(s) 2019.)
- Published
- 2019
- Full Text
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21. Identification and Characterization of Five Cold Stress-Related Rhododendron Dehydrin Genes: Spotlight on a FSK-Type Dehydrin With Multiple F-Segments.
- Author
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Wei H, Yang Y, Himmel ME, Tucker MP, Ding SY, Yang S, and Arora R
- Abstract
Dehydrins are a family of plant proteins that accumulate in response to dehydration stresses, such as low temperature, drought, high salinity, or during seed maturation. We have previously constructed cDNA libraries from Rhododendron catawbiense leaves of naturally non-acclimated (NA; leaf LT
50 , temperature that results in 50% injury of maximum, approximately -7°C) and cold-acclimated (CA; leaf LT50 approximately -50°C) plants and analyzed expressed sequence tags (ESTs). Five ESTs were identified as dehydrin genes. Their full-length cDNA sequences were obtained and designated as RcDhn 1-5 . To explore their functionality vis-à-vis winter hardiness, their seasonal expression kinetics was studied at two levels. Firstly, in leaves of R. catawbiense collected from the NA, CA, and de-acclimated (DA) plants corresponding to summer, winter and spring, respectively. Secondly, in leaves collected monthly from August through February, which progressively increased freezing tolerance from summer through mid-winter. The expression pattern data indicated that RcDhn 1-5 had 6- to 15-fold up-regulation during the cold acclimation process, followed by substantial down-regulation during deacclimation (even back to NA levels for some). Interestingly, our data shows RcDhn 5 contains a histidine-rich motif near N-terminus, a characteristic of metal-binding dehydrins. Equally important, RcDhn 2 contains a consensus 18 amino acid sequence (i.e., ETKDRGLFDFLGKKEEEE) near the N-terminus, with two additional copies upstream, and it is the most acidic (pI of 4.8) among the five RcDhns found. The core of this consensus 18 amino acid sequence is a 11-residue amino acid sequence (DRGLFDFLGKK), recently designated in the literature as the F-segment (based on the pair of hydrophobic F residues it contains). Furthermore, the 208 orthologs of F-segment-containing RcDhn 2 were identified across a broad range of species in GenBank database. This study expands our knowledge about the types of F-segment from the literature-reported single F-segment dehydrins (FSKn ) to two or three F-segment dehydrins: Camelina sativa dehydrin ERD14 as F2 S2 Kn type; and RcDhn 2 as F3 SKn type identified here. Our results also indicate some consensus amino acid sequences flanking the core F-segment in dehydrins. Implications for these cold-responsive RcDhn genes in future genetic engineering efforts to improve plant cold hardiness are discussed.- Published
- 2019
- Full Text
- View/download PDF
22. Production of Jet Fuel-Range Hydrocarbons from Hydrodeoxygenation of Lignin over Super Lewis Acid Combined with Metal Catalysts.
- Author
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Wang H, Wang H, Kuhn E, Tucker MP, and Yang B
- Subjects
- Catalysis, Gas Chromatography-Mass Spectrometry, Mesylates chemistry, Ruthenium chemistry, Hydrocarbons chemical synthesis, Lewis Acids chemistry, Lignin chemistry, Metals chemistry
- Abstract
Super Lewis acids containing the triflate anion [e.g., Hf(OTf)
4 , Ln(OTf)3 , In(OTf)3 , Al(OTf)3 ] and noble metal catalysts (e.g., Ru/C, Ru/Al2 O3 ) formed efficient catalytic systems to generate saturated hydrocarbons from lignin in high yields. In such catalytic systems, the metal triflates mediated rapid ether bond cleavage through selective bonding to etheric oxygens while the noble metal catalyzed subsequent hydrodeoxygenation (HDO) reactions. Near theoretical yields of hydrocarbons were produced from lignin model compounds by the combined catalysis of Hf(OTf)4 and ruthenium-based catalysts. When a technical lignin derived from a pilot-scale biorefinery was used, more than 30 wt % of the hydrocarbons produced with this catalytic system were cyclohexane and alkylcyclohexanes in the jet fuel range. Super Lewis acids are postulated to strongly interact with lignin substrates by protonating hydroxyl groups and ether linkages, forming intermediate species that enhance hydrogenation catalysis by supported noble metal catalysts. Meanwhile, the hydrogenation of aromatic rings by the noble metal catalysts can promote deoxygenation reactions catalyzed by super Lewis acids., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)- Published
- 2018
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23. Evaluation of parameters affecting switchgrass tissue culture: toward a consolidated procedure for Agrobacterium -mediated transformation of switchgrass ( Panicum virgatum ).
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Lin CY, Donohoe BS, Ahuja N, Garrity DM, Qu R, Tucker MP, Himmel ME, and Wei H
- Abstract
Background: Switchgrass ( Panicum virgatum ), a robust perennial C4-type grass, has been evaluated and designated as a model bioenergy crop by the U.S. DOE and USDA. Conventional breeding of switchgrass biomass is difficult because it displays self-incompatible hindrance. Therefore, direct genetic modifications of switchgrass have been considered the more effective approach to tailor switchgrass with traits of interest. Successful transformations have demonstrated increased biomass yields, reduction in the recalcitrance of cell walls and enhanced saccharification efficiency. Several tissue culture protocols have been previously described to produce transgenic switchgrass lines using different nutrient-based media, co-cultivation approaches, and antibiotic strengths for selection., Results: After evaluating the published protocols, we consolidated these approaches and optimized the process to develop a more efficient protocol for producing transgenic switchgrass. First, seed sterilization was optimized, which led to a 20% increase in yield of induced calluses. Second, we have selected a N
6 macronutrient/B5 micronutrient (NB)-based medium for callus induction from mature seeds of the Alamo cultivar, and chose a Murashige and Skoog-based medium to regenerate both Type I and Type II calluses. Third, Agrobacterium -mediated transformation was adopted that resulted in 50-100% positive regenerated transformants after three rounds (2 weeks/round) of selection with antibiotic. Genomic DNA PCR, RT-PCR, Southern blot, visualization of the red fluorescent protein and histochemical β-glucuronidase (GUS) staining were conducted to confirm the positive switchgrass transformants. The optimized methods developed here provide an improved strategy to promote the production and selection of callus and generation of transgenic switchgrass lines., Conclusion: The process for switchgrass transformation has been evaluated and consolidated to devise an improved approach for transgenic switchgrass production. With the optimization of seed sterilization, callus induction, and regeneration steps, a reliable and effective protocol is established to facilitate switchgrass engineering.- Published
- 2017
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24. Undefined cellulase formulations hinder scientific reproducibility.
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Himmel ME, Abbas CA, Baker JO, Bayer EA, Bomble YJ, Brunecky R, Chen X, Felby C, Jeoh T, Kumar R, McCleary BV, Pletschke BI, Tucker MP, Wyman CE, and Decker SR
- Abstract
In the shadow of a burgeoning biomass-to-fuels industry, biological conversion of lignocellulose to fermentable sugars in a cost-effective manner is key to the success of second-generation and advanced biofuel production. For the effective comparison of one cellulase preparation to another, cellulase assays are typically carried out with one or more engineered cellulase formulations or natural exoproteomes of known performance serving as positive controls. When these formulations have unknown composition, as is the case with several widely used commercial products, it becomes impossible to compare or reproduce work done today to work done in the future, where, for example, such preparations may not be available. Therefore, being a critical tenet of science publishing, experimental reproducibility is endangered by the continued use of these undisclosed products. We propose the introduction of standard procedures and materials to produce specific and reproducible cellulase formulations. These formulations are to serve as yardsticks to measure improvements and performance of new cellulase formulations.
- Published
- 2017
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25. Effects of dilute-acid pretreatment conditions on filtration performance of corn stover hydrolyzate.
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Sievers DA, Kuhn EM, Tucker MP, and McMillan JD
- Subjects
- Filtration, Hydrolysis, Sulfuric Acids, Xylose, Carbohydrates, Zea mays
- Abstract
The reaction conditions used during dilute-acid pretreatment of lignocellulosic biomass control the carbohydrate digestion yield and also hydrolyzate properties. Depending on the conversion route of interest, solid-liquid separation (SLS) may be required to split the hemicellulose-rich liquor from the cellulose-rich insoluble solids, and slurry properties are important for SLS. Corn stover was pretreated at different reaction conditions and the slurries were assessed for conversion yield and filtration performance. Increasing pretreatment temperature reduced the solids mean particle size and resulted in slower slurry filtration rates when vacuum filtered or pressure filtered. Corn stover pretreated at 165°C for 10min and with 1% H
2 SO4 exhibited the highest xylose yield and best filtration performance with a no-wash filtration rate of 80kg/hm2 and cake permeability of 15x10-15 ., (Copyright © 2017 Elsevier Ltd. All rights reserved.)- Published
- 2017
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26. One-Pot Process for Hydrodeoxygenation of Lignin to Alkanes Using Ru-Based Bimetallic and Bifunctional Catalysts Supported on Zeolite Y.
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Wang H, Ruan H, Feng M, Qin Y, Job H, Luo L, Wang C, Engelhard MH, Kuhn E, Chen X, Tucker MP, and Yang B
- Subjects
- Catalysis, Microscopy, Electron, Scanning Transmission, X-Ray Diffraction, Alkanes chemistry, Lignin chemistry, Oxygen chemistry, Ruthenium chemistry, Zeolites chemistry
- Abstract
The synthesis of high-efficiency and low-cost catalysts for hydrodeoxygenation (HDO) of waste lignin to advanced biofuels is crucial for enhancing current biorefinery processes. Inexpensive transition metals, including Fe, Ni, Cu, and Zn, were severally co-loaded with Ru on HY zeolite to form bimetallic and bifunctional catalysts. These catalysts were subsequently tested for HDO conversion of softwood lignin and several lignin model compounds. Results indicated that the inexpensive earth-abundant metals could modulate the hydrogenolysis activity of Ru and decrease the yield of low-molecular-weight gaseous products. Among these catalysts, Ru-Cu/HY showed the best HDO performance, affording the highest selectivity to hydrocarbon products. The improved catalytic performance of Ru-Cu/HY was probably a result of the following three factors: (1) high total and strong acid sites, (2) good dispersion of metal species and limited segregation, and (3) high adsorption capacity for polar fractions, including hydroxyl groups and ether bonds. Moreover, all bifunctional catalysts proved to be superior over the combination catalysts of Ru/Al
2 O3 and HY zeolite., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)- Published
- 2017
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27. In situ label-free imaging of hemicellulose in plant cell walls using stimulated Raman scattering microscopy.
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Zeng Y, Yarbrough JM, Mittal A, Tucker MP, Vinzant TB, Decker SR, and Himmel ME
- Abstract
Background: Plant hemicellulose (largely xylan) is an excellent feedstock for renewable energy production and second only to cellulose in abundance. Beyond a source of fermentable sugars, xylan constitutes a critical polymer in the plant cell wall, where its precise role in wall assembly, maturation, and deconstruction remains primarily hypothetical. Effective detection of xylan, particularly by in situ imaging of xylan in the presence of other biopolymers, would provide critical information for tackling the challenges of understanding the assembly and enhancing the liberation of xylan from plant materials., Results: Raman-based imaging techniques, especially the highly sensitive stimulated Raman scattering (SRS) microscopy, have proven to be valuable tools for label-free imaging. However, due to the complex nature of plant materials, especially those same chemical groups shared between xylan and cellulose, the utility of specific Raman vibrational modes that are unique to xylan have been debated. Here, we report a novel approach based on combining spectroscopic analysis and chemical/enzymatic xylan removal from corn stover cell walls, to make progress in meeting this analytical challenge. We have identified several Raman peaks associated with xylan content in cell walls for label-free in situ imaging xylan in plant cell wall., Conclusion: We demonstrated that xylan can be resolved from cellulose and lignin in situ using enzymatic digestion and label-free SRS microscopy in both 2D and 3D. We believe that this novel approach can be used to map xylan in plant cell walls and that this ability will enhance our understanding of the role played by xylan in cell wall biosynthesis and deconstruction.
- Published
- 2016
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28. Directed plant cell-wall accumulation of iron: embedding co-catalyst for efficient biomass conversion.
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Lin CY, Jakes JE, Donohoe BS, Ciesielski PN, Yang H, Gleber SC, Vogt S, Ding SY, Peer WA, Murphy AS, McCann MC, Himmel ME, Tucker MP, and Wei H
- Abstract
Background: Plant lignocellulosic biomass is an abundant, renewable feedstock for the production of biobased fuels and chemicals. Previously, we showed that iron can act as a co-catalyst to improve the deconstruction of lignocellulosic biomass. However, directly adding iron catalysts into biomass prior to pretreatment is diffusion limited, and increases the cost of biorefinery operations. Recently, we developed a new strategy for expressing iron-storage protein ferritin intracellularly to accumulate iron as a catalyst for the downstream deconstruction of lignocellulosic biomass. In this study, we extend this approach by fusing the heterologous ferritin gene with a signal peptide for secretion into Arabidopsis cell walls (referred to here as FerEX)., Results: The transgenic Arabidopsis plants. FerEX. accumulated iron under both normal and iron-fertilized growth conditions; under the latter (iron-fertilized) condition, FerEX transgenic plants showed an increase in plant height and dry weight by 12 and 18 %, respectively, compared with the empty vector control plants. The SDS- and native-PAGE separation of cell-wall protein extracts followed by Western blot analyses confirmed the extracellular expression of ferritin in FerEX plants. Meanwhile, Perls' Prussian blue staining and X-ray fluorescence microscopy (XFM) maps revealed iron depositions in both the secondary and compound middle lamellae cell-wall layers, as well as in some of the corner compound middle lamella in FerEX. Remarkably, their harvested biomasses showed enhanced pretreatability and digestibility, releasing, respectively, 21 % more glucose and 34 % more xylose than the empty vector control plants. These values are significantly higher than those of our recently obtained ferritin intracellularly expressed plants., Conclusions: This study demonstrated that extracellular expression of ferritin in Arabidopsis can produce plants with increased growth and iron accumulation, and reduced thermal and enzymatic recalcitrance. The results are attributed to the intimate colocation of the iron co-catalyst and the cellulose and hemicellulose within the plant cell-wall region, supporting the genetic modification strategy for incorporating conversion catalysts into energy crops prior to harvesting or processing at the biorefinery.
- Published
- 2016
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29. Assessing pretreatment reactor scaling through empirical analysis.
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Lischeske JJ, Crawford NC, Kuhn E, Nagle NJ, Schell DJ, Tucker MP, McMillan JD, and Wolfrum EJ
- Abstract
Background: Pretreatment is a critical step in the biochemical conversion of lignocellulosic biomass to fuels and chemicals. Due to the complexity of the physicochemical transformations involved, predictively scaling up technology from bench- to pilot-scale is difficult. This study examines how pretreatment effectiveness under nominally similar reaction conditions is influenced by pretreatment reactor design and scale using four different pretreatment reaction systems ranging from a 3 g batch reactor to a 10 dry-ton/days continuous reactor. The reactor systems examined were an automated solvent extractor (ASE), steam explosion reactor (SER), ZipperClave
® Reactor (ZCR), and large continuous horizontal screw reactor (LHR). To our knowledge, this is the first such study performed on pretreatment reactors across a range of reaction conditions and at different reactor scales., Results: The comparative pretreatment performance results obtained for each reactor system were used to develop response surface models for total xylose yield after pretreatment and total sugar yield after pretreatment followed by enzymatic hydrolysis. Near- and very-near-optimal regions were defined as the set of conditions that the model identified as producing yields within one and two standard deviations of the optimum yield. Optimal conditions identified in the smallest scale system (the ASE) were within the near-optimal region of the largest scale reactor system evaluated. The maximum total sugar yields for the ASE and LHR were [Formula: see text], while [Formula: see text] was the optimum observed in the ZipperClave., Conclusions: The optimum condition identified using the automated and less costly to operate ASE system was within the very-near-optimal space for the total xylose yield of both the ZCR and the LHR, and was within the near-optimal space for total sugar yield for the LHR. This indicates that the ASE is a good tool for cost effectively finding near-optimal conditions for operating pilot-scale systems. Additionally, using a severity factor approach to optimization was found to be inadequate compared to a multivariate optimization method. Finally, the ASE and the LHR were able to enable significantly higher total sugar yields after enzymatic hydrolysis relative to the ZCR, despite having similar optimal conditions and total xylose yields. This underscores the importance of mechanical disruption during pretreatment to improvement of enzymatic digestibility.- Published
- 2016
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30. Cell wall targeted in planta iron accumulation enhances biomass conversion and seed iron concentration in Arabidopsis and rice.
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Yang H, Wei H, Ma G, Antunes MS, Vogt S, Cox J, Zhang X, Liu X, Bu L, Gleber SC, Carpita NC, Makowski L, Himmel ME, Tucker MP, McCann MC, Murphy AS, and Peer WA
- Subjects
- Arabidopsis genetics, Biofuels, Cell Wall genetics, Oryza genetics, Plant Proteins genetics, Plant Proteins metabolism, Arabidopsis metabolism, Biomass, Cell Wall metabolism, Iron metabolism, Oryza metabolism, Seeds metabolism
- Abstract
Conversion of nongrain biomass into liquid fuel is a sustainable approach to energy demands as global population increases. Previously, we showed that iron can act as a catalyst to enhance the degradation of lignocellulosic biomass for biofuel production. However, direct addition of iron catalysts to biomass pretreatment is diffusion-limited, would increase the cost and complexity of biorefinery unit operations and may have deleterious environmental impacts. Here, we show a new strategy for in planta accumulation of iron throughout the volume of the cell wall where iron acts as a catalyst in the deconstruction of lignocellulosic biomass. We engineered CBM-IBP fusion polypeptides composed of a carbohydrate-binding module family 11 (CBM11) and an iron-binding peptide (IBP) for secretion into Arabidopsis and rice cell walls. CBM-IBP transformed Arabidopsis and rice plants show significant increases in iron accumulation and biomass conversion compared to respective controls. Further, CBM-IBP rice shows a 35% increase in seed iron concentration and a 40% increase in seed yield in greenhouse experiments. CBM-IBP rice potentially could be used to address iron deficiency, the most common and widespread nutritional disorder according to the World Health Organization., (© 2016 The Authors. Plant Biotechnology Journal published by Society for Experimental Biology and The Association of Applied Biologists and John Wiley & Sons Ltd.)
- Published
- 2016
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31. Burkholderia phytofirmans Inoculation-Induced Changes on the Shoot Cell Anatomy and Iron Accumulation Reveal Novel Components of Arabidopsis-Endophyte Interaction that Can Benefit Downstream Biomass Deconstruction.
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Zhao S, Wei H, Lin CY, Zeng Y, Tucker MP, Himmel ME, and Ding SY
- Abstract
It is known that plant growth promoting bacteria (PGPB) elicit positive effects on plant growth and biomass yield. However, the actual mechanism behind the plant-PGPB interaction is poorly understood, and the literature is scarce regarding the thermochemical pretreatability and enzymatic degradability of biomass derived from PGPB-inoculated plants. Most recent transcriptional analyses of PGPB strain Burkholderia phytofirmans PsJN inoculating potato in literature and Arabidopsis in our present study have revealed the expression of genes for ferritin and the biosynthesis and transport of siderophores (i.e., the molecules with high affinity for iron), respectively. The expression of such genes in the shoots of PsJN-inoculated plants prompted us to propose that PsJN-inoculation can improve the host plant's iron uptake and accumulation, which facilitates the downstream plant biomass pretreatment and conversion to simple sugars. In this study, we employed B. phytofirmans PsJN to inoculate the Arabidopsis thaliana plants, and conducted the first investigation for its effects on the biomass yield, the anatomical organization of stems, the iron accumulation, and the pretreatment and enzymatic hydrolysis of harvested biomass. The results showed that the strain PsJN stimulated plant growth in the earlier period of plant development and enlarged the cell size of stem piths, and it also indeed enhanced the essential metals uptake and accumulation in host plants. Moreover, we found that the PsJN-inoculated plant biomass released more glucose and xylose after hot water pretreatment and subsequent co-saccharification, which provided a novel insight into development of lignocellulosic biofuels from renewable biomass resources.
- Published
- 2016
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32. Techno-economic analysis of the deacetylation and disk refining process: characterizing the effect of refining energy and enzyme usage on minimum sugar selling price and minimum ethanol selling price.
- Author
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Chen X, Shekiro J, Pschorn T, Sabourin M, Tucker MP, and Tao L
- Abstract
Background: A novel, highly efficient deacetylation and disk refining (DDR) process to liberate fermentable sugars from biomass was recently developed at the National Renewable Energy Laboratory (NREL). The DDR process consists of a mild, dilute alkaline deacetylation step followed by low-energy-consumption disk refining. The DDR corn stover substrates achieved high process sugar conversion yields, at low to modest enzyme loadings, and also produced high sugar concentration syrups at high initial insoluble solid loadings. The sugar syrups derived from corn stover are highly fermentable due to low concentrations of fermentation inhibitors. The objective of this work is to evaluate the economic feasibility of the DDR process through a techno-economic analysis (TEA)., Results: A large array of experiments designed using a response surface methodology was carried out to investigate the two major cost-driven operational parameters of the novel DDR process: refining energy and enzyme loadings. The boundary conditions for refining energy (128-468 kWh/ODMT), cellulase (Novozyme's CTec3) loading (11.6-28.4 mg total protein/g of cellulose), and hemicellulase (Novozyme's HTec3) loading (0-5 mg total protein/g of cellulose) were chosen to cover the most commercially practical operating conditions. The sugar and ethanol yields were modeled with good adequacy, showing a positive linear correlation between those yields and refining energy and enzyme loadings. The ethanol yields ranged from 77 to 89 gallons/ODMT of corn stover. The minimum sugar selling price (MSSP) ranged from $0.191 to $0.212 per lb of 50 % concentrated monomeric sugars, while the minimum ethanol selling price (MESP) ranged from $2.24 to $2.54 per gallon of ethanol., Conclusions: The DDR process concept is evaluated for economic feasibility through TEA. The MSSP and MESP of the DDR process falls within a range similar to that found with the deacetylation/dilute acid pretreatment process modeled in NREL's 2011 design report. The DDR process is a much simpler process that requires less capital and maintenance costs when compared to conventional chemical pretreatments with pressure vessels. As a result, we feel the DDR process should be considered as an option for future biorefineries with great potential to be more cost-effective.
- Published
- 2015
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33. High-throughput Screening of Recalcitrance Variations in Lignocellulosic Biomass: Total Lignin, Lignin Monomers, and Enzymatic Sugar Release.
- Author
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Decker SR, Sykes RW, Turner GB, Lupoi JS, Doepkke C, Tucker MP, Schuster LA, Mazza K, Himmel ME, Davis MF, and Gjersing E
- Subjects
- Carbohydrates chemistry, Chromatography, High Pressure Liquid methods, Glucose analysis, High-Throughput Screening Assays methods, Plants chemistry, Xylose analysis, Biomass, Carbohydrates analysis, Lignin chemistry
- Abstract
The conversion of lignocellulosic biomass to fuels, chemicals, and other commodities has been explored as one possible pathway toward reductions in the use of non-renewable energy sources. In order to identify which plants, out of a diverse pool, have the desired chemical traits for downstream applications, attributes, such as cellulose and lignin content, or monomeric sugar release following an enzymatic saccharification, must be compared. The experimental and data analysis protocols of the standard methods of analysis can be time-consuming, thereby limiting the number of samples that can be measured. High-throughput (HTP) methods alleviate the shortcomings of the standard methods, and permit the rapid screening of available samples to isolate those possessing the desired traits. This study illustrates the HTP sugar release and pyrolysis-molecular beam mass spectrometry pipelines employed at the National Renewable Energy Lab. These pipelines have enabled the efficient assessment of thousands of plants while decreasing experimental time and costs through reductions in labor and consumables.
- Published
- 2015
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34. In situ micro-spectroscopic investigation of lignin in poplar cell walls pretreated by maleic acid.
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Zeng Y, Zhao S, Wei H, Tucker MP, Himmel ME, Mosier NS, Meilan R, and Ding SY
- Abstract
Background: In higher plant cells, lignin provides necessary physical support for plant growth and resistance to attack by microorganisms. For the same reason, lignin is considered to be a major impediment to the process of deconstructing biomass to simple sugars by hydrolytic enzymes. The in situ variation of lignin in plant cell walls is important for better understanding of the roles lignin play in biomass recalcitrance., Results: A micro-spectroscopic approach combining stimulated Raman scattering microscopy and fluorescence lifetime imaging microscopy was employed to probe the physiochemical structure of lignin in poplar tracheid cell walls. Two forms of lignins were identified: loosely packed lignin, which had a long (4 ns) fluorescence lifetime and existed primarily in the secondary wall layers; and dense lignin, which had a short (0.5-1 ns) fluorescence lifetime and was present in all wall layers, including the cell corners, compound middle lamellae, and secondary wall. At low maleic acid concentration (0.025 and 0.05 M) pretreatment conditions, some of the dense lignin was modified to become more loosely packed. High acid concentration removed both dense and loosely packed lignins. These modified lignins reformed to make lignin-carbohydrate complex droplets containing either dense or loosely packed lignin (mostly from secondary walls) and were commonly observed on the cell wall surface., Conclusions: We have identified dense and loosely packed lignins in plant cell walls. During maleic acid pretreatment, both dense lignin droplets and loosely packed lignin droplets were formed. Maleic acid pretreatment more effectively removes loosely packed lignin in secondary walls which increases enzyme accessibility for digestion.
- Published
- 2015
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35. Identifying the ionically bound cell wall and intracellular glycoside hydrolases in late growth stage Arabidopsis stems: implications for the genetic engineering of bioenergy crops.
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Wei H, Brunecky R, Donohoe BS, Ding SY, Ciesielski PN, Yang S, Tucker MP, and Himmel ME
- Abstract
Identifying the cell wall-ionically bound glycoside hydrolases (GHs) in Arabidopsis stems is important for understanding the regulation of cell wall integrity. For cell wall proteomics studies, the preparation of clean cell wall fractions is a challenge since cell walls constitute an open compartment, which is more likely to contain a mixture of intracellular and extracellular proteins due to cell leakage at the late growth stage. Here, we utilize a CaCl2-extraction procedure to isolate non-structural proteins from Arabidopsis whole stems, followed by the in-solution and in-gel digestion methods coupled with Nano-LC-MS/MS, bioinformatics and literature analyses. This has led to the identification of 75 proteins identified using the in-solution method and 236 proteins identified by the in-gel method, among which about 10% of proteins predicted to be secreted. Together, eight cell wall proteins, namely AT1G75040, AT5G26000, AT3G57260, AT4G21650, AT3G52960, AT3G49120, AT5G49360, and AT3G14067, were identified by the in-solution method; among them, three were the GHs (AT5G26000, myrosinase 1, GH1; AT3G57260, β-1,3-glucanase 2, GH17; AT5G49360, bifunctional XYL 1/α-L-arabinofuranosidase, GH3). Moreover, four more GHs: AT4G30270 (xyloglucan endotransferase, GH16), AT1G68560 (bifunctional α-l-arabinofuranosidase/XYL, GH31), AT1G12240 (invertase, GH32) and AT2G28470 (β-galactosidase 8, GH35), were identified by the in-gel solution method only. Notably, more than half of above identified GHs are xylan- or hemicellulose-modifying enzymes, and will likely have an impact on cellulose accessibility, which is a critical factor for downstream enzymatic hydrolysis of plant tissues for biofuels production. The implications of these cell wall proteins identified at the late growth stage for the genetic engineering of bioenergy crops are discussed.
- Published
- 2015
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36. Controlling porosity in lignin-derived nanoporous carbon for supercapacitor applications.
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Jeon JW, Zhang L, Lutkenhaus JL, Laskar DD, Lemmon JP, Choi D, Nandasiri MI, Hashmi A, Xu J, Motkuri RK, Fernandez CA, Liu J, Tucker MP, McGrail PB, Yang B, and Nune SK
- Subjects
- Porosity, Carbon chemistry, Electric Capacitance, Lignin chemistry, Nanopores
- Published
- 2015
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37. High temperature pre-digestion of corn stover biomass for improved product yields.
- Author
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Brunecky R, Hobdey SE, Taylor LE 2nd, Tao L, Tucker MP, Himmel ME, and Decker SR
- Abstract
Introduction: The efficient conversion of lignocellulosic feedstocks remains a key step in the commercialization of biofuels. One of the barriers to cost-effective conversion of lignocellulosic biomass to sugars remains the enzymatic saccharification process step. Here, we describe a novel hybrid processing approach comprising enzymatic pre-digestion with newly characterized hyperthermophilic enzyme cocktails followed by conventional saccharification with commercial enzyme preparations. Dilute acid pretreated corn stover was subjected to this new procedure to test its efficacy. Thermal tolerant enzymes from Acidothermus cellulolyticus and Caldicellulosiruptor bescii were used to pre-digest pretreated biomass at elevated temperatures prior to saccharification by the commercial cellulase formulation., Results: We report that pre-digestion of biomass with these enzymes at elevated temperatures prior to addition of the commercial cellulase formulation increased conversion rates and yields when compared to commercial cellulase formulation alone under low solids conditions., Conclusion: Our results demonstrating improvements in rates and yields of conversion point the way forward for hybrid biomass conversion schemes utilizing catalytic amounts of hyperthermophilic enzymes.
- Published
- 2014
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38. Comparison of transcriptional profiles of Clostridium thermocellum grown on cellobiose and pretreated yellow poplar using RNA-Seq.
- Author
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Wei H, Fu Y, Magnusson L, Baker JO, Maness PC, Xu Q, Yang S, Bowersox A, Bogorad I, Wang W, Tucker MP, Himmel ME, and Ding SY
- Abstract
The anaerobic, thermophilic bacterium, Clostridium thermocellum, secretes multi-protein enzyme complexes, termed cellulosomes, which synergistically interact with the microbial cell surface and efficiently disassemble plant cell wall biomass. C. thermocellum has also been considered a potential consolidated bioprocessing (CBP) organism due to its ability to produce the biofuel products, hydrogen, and ethanol. We found that C. thermocellum fermentation of pretreated yellow poplar (PYP) produced 30 and 39% of ethanol and hydrogen product concentrations, respectively, compared to fermentation of cellobiose. RNA-seq was used to analyze the transcriptional profiles of these cells. The PYP-grown cells taken for analysis at the late stationary phase showed 1211 genes up-regulated and 314 down-regulated by more than two-fold compared to the cellobiose-grown cells. These affected genes cover a broad spectrum of specific functional categories. The transcriptional analysis was further validated by sub-proteomics data taken from the literature; as well as by quantitative reverse transcription-PCR (qRT-PCR) analyses of selected genes. Specifically, 47 cellulosomal protein-encoding genes, genes for 4 pairs of SigI-RsgI for polysaccharide sensing, 7 cellodextrin ABC transporter genes, and a set of NAD(P)H hydogenase and alcohol dehydrogenase genes were up-regulated for cells growing on PYP compared to cellobiose. These genes could be potential candidates for future studies aimed at gaining insight into the regulatory mechanism of this organism as well as for improvement of C. thermocellum in its role as a CBP organism.
- Published
- 2014
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39. Effect of mechanical disruption on the effectiveness of three reactors used for dilute acid pretreatment of corn stover Part 1: chemical and physical substrate analysis.
- Author
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Wang W, Chen X, Donohoe BS, Ciesielski PN, Katahira R, Kuhn EM, Kafle K, Lee CM, Park S, Kim SH, Tucker MP, Himmel ME, and Johnson DK
- Abstract
Background: There is considerable interest in the conversion of lignocellulosic biomass to liquid fuels to provide substitutes for fossil fuels. Pretreatments, conducted to reduce biomass recalcitrance, usually remove at least some of the hemicellulose and/or lignin in cell walls. The hypothesis that led to this research was that reactor type could have a profound effect on the properties of pretreated materials and impact subsequent cellulose hydrolysis., Results: Corn stover was dilute-acid pretreated using commercially relevant reactor types (ZipperClave(®) (ZC), Steam Gun (SG) and Horizontal Screw (HS)) under the same nominal conditions. Samples produced in the SG and HS achieved much higher cellulose digestibilities (88% and 95%, respectively), compared to the ZC sample (68%). Characterization, by chemical, physical, spectroscopic and electron microscopy methods, was used to gain an understanding of the effects causing the digestibility differences. Chemical differences were small; however, particle size differences appeared significant. Sum-frequency generation vibrational spectra indicated larger inter-fibrillar spacing or randomization of cellulose microfibrils in the HS sample. Simons' staining indicated increased cellulose accessibility for the SG and HS samples. Electron microscopy showed that the SG and HS samples were more porous and fibrillated because of mechanical grinding and explosive depressurization occurring with these two reactors. These structural changes most likely permitted increased cellulose accessibility to enzymes, enhancing saccharification., Conclusions: Dilute-acid pretreatment of corn stover using three different reactors under the same nominal conditions gave samples with very different digestibilities, although chemical differences in the pretreated substrates were small. The results of the physical and chemical analyses of the samples indicate that the explosive depressurization and mechanical grinding with these reactors increased enzyme accessibility. Pretreatment reactors using physical force to disrupt cell walls increase the effectiveness of the pretreatment process.
- Published
- 2014
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40. Effect of mechanical disruption on the effectiveness of three reactors used for dilute acid pretreatment of corn stover Part 2: morphological and structural substrate analysis.
- Author
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Ciesielski PN, Wang W, Chen X, Vinzant TB, Tucker MP, Decker SR, Himmel ME, Johnson DK, and Donohoe BS
- Abstract
Background: Lignocellulosic biomass is a renewable, naturally mass-produced form of stored solar energy. Thermochemical pretreatment processes have been developed to address the challenge of biomass recalcitrance, however the optimization, cost reduction, and scalability of these processes remain as obstacles to the adoption of biofuel production processes at the industrial scale. In this study, we demonstrate that the type of reactor in which pretreatment is carried out can profoundly alter the micro- and nanostructure of the pretreated materials and dramatically affect the subsequent efficiency, and thus cost, of enzymatic conversion of cellulose., Results: Multi-scale microscopy and quantitative image analysis was used to investigate the impact of different biomass pretreatment reactor configurations on plant cell wall structure. We identify correlations between enzymatic digestibility and geometric descriptors derived from the image data. Corn stover feedstock was pretreated under the same nominal conditions for dilute acid pretreatment (2.0 wt% H2SO4, 160°C, 5 min) using three representative types of reactors: ZipperClave® (ZC), steam gun (SG), and horizontal screw (HS) reactors. After 96 h of enzymatic digestion, biomass treated in the SG and HS reactors achieved much higher cellulose conversions, 88% and 95%, respectively, compared to the conversion obtained using the ZC reactor (68%). Imaging at the micro- and nanoscales revealed that the superior performance of the SG and HS reactors could be explained by reduced particle size, cellular dislocation, increased surface roughness, delamination, and nanofibrillation generated within the biomass particles during pretreatment., Conclusions: Increased cellular dislocation, surface roughness, delamination, and nanofibrillation revealed by direct observation of the micro- and nanoscale change in accessibility explains the superior performance of reactors that augment pretreatment with physical energy.
- Published
- 2014
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41. Characterization of pilot-scale dilute acid pretreatment performance using deacetylated corn stover.
- Author
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Shekiro Iii J, Kuhn EM, Nagle NJ, Tucker MP, Elander RT, and Schell DJ
- Abstract
Background: Dilute acid pretreatment is a promising process technology for the deconstruction of low-lignin lignocellulosic biomass, capable of producing high yields of hemicellulosic sugars and enhancing enzymatic yields of glucose as part of a biomass-to-biofuels process. However, while it has been extensively studied, most work has historically been conducted at relatively high acid concentrations of 1 - 4% (weight/weight). Reducing the effective acid loading in pretreatment has the potential to reduce chemical costs both for pretreatment and subsequent neutralization. Additionally, if acid loadings are sufficiently low, capital requirements associated with reactor construction may be significantly reduced due to the relaxation of requirements for exotic alloys. Despite these benefits, past efforts have had difficulty obtaining high process yields at low acid loadings without supplementation of additional unit operations, such as mechanical refining., Results: Recently, we optimized the dilute acid pretreatment of deacetylated corn stover at low acid loadings in a 1-ton per day horizontal pretreatment reactor. This effort included more than 25 pilot-scale pretreatment experiments executed at reactor temperatures ranging from 150 - 170°C, residence times of 10 - 20 minutes and hydrolyzer sulfuric acid concentrations between 0.15 - 0.30% (weight/weight). In addition to characterizing the process yields achieved across the reaction space, the optimization identified a pretreatment reaction condition that achieved total xylose yields from pretreatment of 73.5% ± 1.5% with greater than 97% xylan component balance closure across a series of five runs at the same condition. Feedstock reactivity at this reaction condition after bench-scale high solids enzymatic hydrolysis was 77%, prior to the inclusion of any additional conversion that may occur during subsequent fermentation., Conclusions: This study effectively characterized a range of pretreatment reaction conditions using deacetylated corn stover at low acid loadings and identified an optimum reaction condition was selected and used in a series of integrated pilot scale cellulosic ethanol production campaigns. Additionally, several issues exist to be considered in future pretreatment experiments in continuous reactor systems, including the formation of char within the reactor, as well as practical issues with feeding herbaceous feedstock into pressurized systems.
- Published
- 2014
- Full Text
- View/download PDF
42. 3D electron tomography of pretreated biomass informs atomic modeling of cellulose microfibrils.
- Author
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Ciesielski PN, Matthews JF, Tucker MP, Beckham GT, Crowley MF, Himmel ME, and Donohoe BS
- Subjects
- Cell Membrane chemistry, Computer Simulation, Fibrillar Collagens chemistry, Models, Chemical, Protein Conformation, Zea mays chemistry, Cell Membrane ultrastructure, Electron Microscope Tomography methods, Fibrillar Collagens ultrastructure, Imaging, Three-Dimensional methods, Models, Molecular, Molecular Imaging methods, Zea mays ultrastructure
- Abstract
Fundamental insights into the macromolecular architecture of plant cell walls will elucidate new structure-property relationships and facilitate optimization of catalytic processes that produce fuels and chemicals from biomass. Here we introduce computational methodology to extract nanoscale geometry of cellulose microfibrils within thermochemically treated biomass directly from electron tomographic data sets. We quantitatively compare the cell wall nanostructure in corn stover following two leading pretreatment strategies: dilute acid with iron sulfate co-catalyst and ammonia fiber expansion (AFEX). Computational analysis of the tomographic data is used to extract mathematical descriptions for longitudinal axes of cellulose microfibrils from which we calculate their nanoscale curvature. These nanostructural measurements are used to inform the construction of atomistic models that exhibit features of cellulose within real, process-relevant biomass. By computational evaluation of these atomic models, we propose relationships between the crystal structure of cellulose Iβ and the nanoscale geometry of cellulose microfibrils.
- Published
- 2013
- Full Text
- View/download PDF
43. Tracking dynamics of plant biomass composting by changes in substrate structure, microbial community, and enzyme activity.
- Author
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Wei H, Tucker MP, Baker JO, Harris M, Luo Y, Xu Q, Himmel ME, and Ding SY
- Abstract
Background: Understanding the dynamics of the microbial communities that, along with their secreted enzymes, are involved in the natural process of biomass composting may hold the key to breaking the major bottleneck in biomass-to-biofuels conversion technology, which is the still-costly deconstruction of polymeric biomass carbohydrates to fermentable sugars.However, the complexity of both the structure of plant biomass and its counterpart microbial degradation communities makes it difficult to investigate the composting process., Results: In this study, a composter was set up with a mix of yellow poplar (Liriodendron tulipifera) wood-chips and mown lawn grass clippings (85:15 in dry-weight) and used as a model system. The microbial rDNA abundance data obtained from analyzing weekly-withdrawn composted samples suggested population-shifts from bacteria-dominated to fungus-dominated communities. Further analyses by an array of optical microscopic, transcriptional and enzyme-activity techniques yielded correlated results, suggesting that such population shifts occurred along with early removal of hemicellulose followed by attack on the consequently uncovered cellulose as the composting progressed., Conclusion: The observed shifts in dominance by representative microbial groups, along with the observed different patterns in the gene expression and enzymatic activities between cellulases, hemicellulases, and ligninases during the composting process, provide new perspectives for biomass-derived biotechnology such as consolidated bioprocessing (CBP) and solid-state fermentation for the production of cellulolytic enzymes and biofuels.
- Published
- 2012
- Full Text
- View/download PDF
44. The impacts of deacetylation prior to dilute acid pretreatment on the bioethanol process.
- Author
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Chen X, Shekiro J, Franden MA, Wang W, Zhang M, Kuhn E, Johnson DK, and Tucker MP
- Abstract
Background: Dilute acid pretreatment is a promising pretreatment technology for the biochemical production of ethanol from lignocellulosic biomass. During dilute acid pretreatment, xylan depolymerizes to form soluble xylose monomers and oligomers. Because the xylan found in nature is highly acetylated, the formation of xylose monomers requires two steps: 1) cleavage of the xylosidic bonds, and 2) cleavage of covalently bonded acetyl ester groups., Results: In this study, we show that the latter may be the rate limiting step for xylose monomer formation. Furthermore, acetyl groups are also found to be a cause of biomass recalcitrance and hydrolyzate toxicity. While the removal of acetyl groups from native corn stover by alkaline de-esterification prior to pretreatment improves overall process yields, the exact impact is highly dependent on the corn stover variety in use. Xylose monomer yields in pretreatment generally increases by greater than 10%. Compared to pretreated corn stover controls, the deacetylated corn stover feedstock is approximately 20% more digestible after pretreatment. Finally, by lowering hydrolyzate toxicity, xylose utilization and ethanol yields are further improved during fermentation by roughly 10% and 7%, respectively. In this study, several varieties of corn stover lots were investigated to test the robustness of the deacetylation-pretreatment-saccharification-fermentation process., Conclusions: Deacetylation shows significant improvement on glucose and xylose yields during pretreatment and enzymatic hydrolysis, but it also reduces hydrolyzate toxicity during fermentation, thereby improving ethanol yields and titer. The magnitude of effect is dependent on the selected corn stover variety, with several varieties achieving improvements of greater than 10% xylose yield in pretreatment, 20% glucose yield in low solids enzymatic hydrolysis and 7% overall ethanol yield.
- Published
- 2012
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45. Elucidating the role of ferrous ion cocatalyst in enhancing dilute acid pretreatment of lignocellulosic biomass.
- Author
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Wei H, Donohoe BS, Vinzant TB, Ciesielski PN, Wang W, Gedvilas LM, Zeng Y, Johnson DK, Ding SY, Himmel ME, and Tucker MP
- Abstract
Background: Recently developed iron cocatalyst enhancement of dilute acid pretreatment of biomass is a promising approach for enhancing sugar release from recalcitrant lignocellulosic biomass. However, very little is known about the underlying mechanisms of this enhancement. In the current study, our aim was to identify several essential factors that contribute to ferrous ion-enhanced efficiency during dilute acid pretreatment of biomass and to initiate the investigation of the mechanisms that result in this enhancement., Results: During dilute acid and ferrous ion cocatalyst pretreatments, we observed concomitant increases in solubilized sugars in the hydrolysate and reducing sugars in the (insoluble) biomass residues. We also observed enhancements in sugar release during subsequent enzymatic saccharification of iron cocatalyst-pretreated biomass. Fourier transform Raman spectroscopy showed that major peaks representing the C-O-C and C-H bonds in cellulose are significantly attenuated by iron cocatalyst pretreatment. Imaging using Prussian blue staining indicated that Fe2+ ions associate with both cellulose/xylan and lignin in untreated as well as dilute acid/Fe2+ ion-pretreated corn stover samples. Analyses by scanning electron microscopy and transmission electron microscopy revealed structural details of biomass after dilute acid/Fe2+ ion pretreatment, in which delamination and fibrillation of the cell wall were observed., Conclusions: By using this multimodal approach, we have revealed that (1) acid-ferrous ion-assisted pretreatment increases solubilization and enzymatic digestion of both cellulose and xylan to monomers and (2) this pretreatment likely targets multiple chemistries in plant cell wall polymer networks, including those represented by the C-O-C and C-H bonds in cellulose.
- Published
- 2011
- Full Text
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46. High throughput determination of glucan and xylan fractions in lignocelluloses.
- Author
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Selig MJ, Tucker MP, Law C, Doeppke C, Himmel ME, and Decker SR
- Subjects
- Carbohydrate Dehydrogenases metabolism, Glucose Oxidase metabolism, Glucans analysis, High-Throughput Screening Assays methods, Lignin chemistry, Xylans analysis
- Abstract
The analysis of structural glucan and xylan in lignocellulose was scaled down from original two-stage sulfuric acid hydrolysis methods (Moore WE and Johnson DB 1967 Procedures for the chemical analysis of wood and wood products. U.S. Forest Products Laboratory, U.S. Department of Agriculture., Madison, WI) and integrated into a recently-developed, high throughput pretreatment and enzymatic saccharification system. Novel 96×1.8 ml-well Hastelloy reactor plates (128×86×51 mm) based on previously described 96-well pretreatment reactor plates were paired with custom aluminum filler plates (128×86×18 mm) for use in Symyx Powdernium solids dispensing systems. The incorporation of glucose oxidase and xylose dehydrogenase linked assays to speed post-hydrolysis sugar analysis dramatically reduced the time for analysis of large lignocellulosic sample sets. The current system permits the determination of the glucan and xylan content of 96 replicates (per reactor plate) in under 6 h and parallel plate processing increases the analysis throughput substantially., (© Springer Science+Business Media B.V. (outside the USA) 2011)
- Published
- 2011
- Full Text
- View/download PDF
47. Natural paradigms of plant cell wall degradation.
- Author
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Wei H, Xu Q, Taylor LE 2nd, Baker JO, Tucker MP, and Ding SY
- Subjects
- Bacteria metabolism, Biodegradation, Environmental, Biomass, Cell Communication physiology, Cell Wall metabolism, Plants metabolism
- Abstract
Natural processes of recycling carbon from plant cell walls are slow but very efficient, generally involving microbial communities and their secreted enzymes. Efficient combinations of microbial communities and enzymes act in a sequential and synergistic manner to degrade plant cell walls. Recent understanding of plant cell wall ultra-structure, as well as the carbon metabolism, ATP production, and ecology of participating microbial communities, and the biochemical properties of their cellulolytic enzymes have led to new perspectives on saccharification of biomass. Microbial communities are dynamic functions of the chemical and structural compositions of plant cell wall components. The primitive 'multicellularity' exhibited by certain cellulolytic microorganisms may play a role in facilitating cell-cell communication and cell-plant cell wall-substrate interaction.
- Published
- 2009
- Full Text
- View/download PDF
48. High xylose yields from dilute acid pretreatment of corn stover under process-relevant conditions.
- Author
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Weiss ND, Nagle NJ, Tucker MP, and Elander RT
- Subjects
- Bioreactors, Biotechnology, Particle Size, Temperature, Zea mays chemistry, Sulfuric Acids chemistry, Xylose biosynthesis, Zea mays metabolism
- Abstract
Pretreatment experiments were carried out to demonstrate high xylose yields at high solids loadings in two different batch pretreatment reactors under process-relevant conditions. Corn stover was pretreated with dilute sulfuric acid using a 4-l Steam Digester and a 4-l stirred ZipperClave reactor. Solids were loaded at 45% dry matter (wt/wt) after sulfuric acid catalyst impregnation using nominal particle sizes of either 6 or 18 mm. Pretreatment was carried out at temperatures between 180 and 200 degrees C at residence times of either 90 or 105 s. Results demonstrate an ability to achieve high xylose yields (>80%) over a range of pretreatment conditions, with performance showing little dependence on particle size or pretreatment reactor type. The high xylose yields are attributed to effective catalyst impregnation and rapid rates of heat transfer during pretreatment.
- Published
- 2009
- Full Text
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49. Visualizing lignin coalescence and migration through maize cell walls following thermochemical pretreatment.
- Author
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Donohoe BS, Decker SR, Tucker MP, Himmel ME, and Vinzant TB
- Subjects
- Biotechnology methods, Dimerization, Heating, Hydrolysis, Immunohistochemistry, Lignin metabolism, Magnetic Resonance Spectroscopy, Microscopy, Electron, Scanning, Monosaccharides chemistry, Phase Transition, Spectroscopy, Fourier Transform Infrared, Sulfuric Acids, Zea mays ultrastructure, Cell Wall metabolism, Lignin chemistry, Zea mays chemistry, Zea mays metabolism
- Abstract
Plant cell walls are composed primarily of cellulose, hemicelluloses, lignins, and pectins. Of these components, lignins exhibit unique chemistry and physiological functions. Although lignins can be used as a product feedstock or as a fuel, lignins are also generally seen as a barrier to efficient enzymatic breakdown of biomass to sugars. Indeed, many pretreatment strategies focus on removing a significant fraction of lignin from biomass to better enable saccharification. In order to better understand the fate of biomass lignins that remain with the solids following dilute acid pretreatment, we undertook a structural investigation to track lignins on and in biomass cell walls. SEM and TEM imaging revealed a range of droplet morphologies that appear on and within cell walls of pretreated biomass; as well as the specific ultrastructural regions that accumulate the droplets. These droplets were shown to contain lignin by FTIR, NMR, antibody labeling, and cytochemical staining. We provide evidence supporting the idea that thermochemical pretreatments reaching temperatures above the range for lignin phase transition cause lignins to coalesce into larger molten bodies that migrate within and out of the cell wall, and can redeposit on the surface of plant cell walls. This decompartmentalization and relocalization of lignins is likely to be at least as important as lignin removal in the quest to improve the digestibility of biomass for sugars and fuels production.
- Published
- 2008
- Full Text
- View/download PDF
50. Deposition of lignin droplets produced during dilute acid pretreatment of maize stems retards enzymatic hydrolysis of cellulose.
- Author
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Selig MJ, Viamajala S, Decker SR, Tucker MP, Himmel ME, and Vinzant TB
- Subjects
- Hydrogen-Ion Concentration, Hydrolysis, Temperature, Biomass, Cellulases metabolism, Cellulose chemistry, Lignin biosynthesis, Zea mays metabolism
- Abstract
Electron microscopy of lignocellulosic biomass following high-temperature pretreatment revealed the presence of spherical formations on the surface of the residual biomass. The hypothesis that these droplet formations are composed of lignins and possible lignin carbohydrate complexes is being explored. Experiments were conducted to better understand the formation of these "lignin" droplets and the possible implications they might have on the enzymatic saccharification of pretreated biomass. It was demonstrated that these droplets are produced from corn stover during pretreatment under neutral and acidic pH at and above 130 degrees C, and that they can deposit back onto the surface of residual biomass. The deposition of droplets produced under certain pretreatment conditions (acidic pH; T > 150 degrees C) and captured onto pure cellulose was shown to have a negative effect (5-20%) on the enzymatic saccharification of this substrate. It was noted that droplet density (per unit area) was greater and droplet size more variable under conditions where the greatest impact on enzymatic cellulose conversion was observed. These results indicate that this phenomenon has the potential to adversely affect the efficiency of enzymatic conversion in a lignocellulosic biorefinery.
- Published
- 2007
- Full Text
- View/download PDF
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