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The commercial production of bioethanol from lignocellulosic biomass such as wheat straw requires utilizing a microorganism that can withstand all the stressors encountered in the process while fermenting all the sugars in the biomass. Therefore, it is essential to develop tools for monitoring and controlling the cellular fitness during both cell propagation and sugar fermentation to ethanol. In the present study, on-line flow cytometry was adopted to assess the response of the biosensor TRX2p-yEGFP for redox imbalance in an industrial xylose-fermenting strain of Saccharomyces cerevisiae during cell propagation and the following fermentation of wheat-straw hydrolysate. Rapid and transient induction of the sensor was recorded upon exposure to furfural and wheat straw hydrolysate containing up to 3.8 g/L furfural. During the fermentation step, the induction rate of the sensor was also found to correlate to the initial ethanol production rate, highlighting the relevance of redox monitoring and the potential of the presented tool to assess the ethanol production rate in hydrolysates. Three different propagation strategies were also compared, and it was confirmed that pre-exposure to hydrolysate during propagation remains the most efficient method for high ethanol productivity in the following wheat-straw hydrolysate fermentations. [ABSTRACT FROM AUTHOR]

Article Highlights Fiber size reduction benefits enzymatic high gravity hydrolysis of steam-exploded wheat straw. Small fiber size of ≤ 2.5 mm enables saccharification at 35% w/w solid loadings. Water-retention capacity of cellulosic fibers influence slurry viscosity and yielded glucose concentration.

Crop residues derived from post-harvesting process have been problematic due to an on-field incineration, which caused air pollutants and greenhouse gas (GHG) emissions. An appropriate utilization of those biomasses can improve the environmental situation and provide a substitute for fossil fuels. Therefore, this study intends to analyze how left-over agricultural residues should be valorized in the decentralized bioethanol production configuration. With integrated techniques of geographical information system and multi-criteria analysis (GIS-MCA), we identify suitable locations for exhibiting decentralized sites matching the geographical backgrounds in each region. Under the precondition of a complete utilization of the agricultural residues, we found optimal installation numbers 71 units of decentralized production in total through suitability analysis. Conducting the location–allocation model, it is possible to determine production scales from the collectable spatially distributed biomass and transportation distances. Under the presumed conditions of installing 1 to 25 units, the logistics cost and total capital investment can reach USD 1.17–2.46 L−1 and USD 1.17–6.93 L−1, respectively. The results from examining the technical potential and economic feasibility aspects are key to designing decentralized bioethanol production facilities and maximizing the utilization of agricultural residues in Thailand. [ABSTRACT FROM AUTHOR]

The commercial production of bioethanol from lignocellulosic biomass such as wheat straw requires utilizing a microorganism that can withstand all the stressors encountered in the process while fermenting all the sugars in the biomass. Therefore, it is essential to develop tools for monitoring and controlling the cellular fitness during both cell propagation and sugar fermentation to ethanol. In the present study, on-line flow cytometry was adopted to assess the response of the biosensor TRX2p-yEGFP for redox imbalance in an industrial xylose-fermenting strain of Saccharomyces cerevisiae during cell propagation and the following fermentation of wheat-straw hydrolysate. Rapid and transient induction of the sensor was recorded upon exposure to furfural and wheat straw hydrolysate containing up to 3.8 g/L furfural. During the fermentation step, the induction rate of the sensor was also found to correlate to the initial ethanol production rate, highlighting the relevance of redox monitoring and the potential of the presented tool to assess the ethanol production rate in hydrolysates. Three different propagation strategies were also compared, and it was confirmed that pre-exposure to hydrolysate during propagation remains the most efficient method for high ethanol productivity in the following wheat-straw hydrolysate fermentations.

To reduce greenhouse gas (GHG) emissions, the European Union (EU) has targets for utilizing energy from renewable sources. By 2030, a minimum of 3.5% of energy in the EU’s transport sector should come from renewable biological sources, such as crop residues. This paper analyzed EU’s “advanced bioethanol” potential from wheat straw and maize stover and evaluated its environmental (land, water, and carbon) footprint. We differentiated between gross and net bioethanol output, the latter by subtracting the energy inputs in production. Results suggest that the annual amount of the sustainably harvestable wheat straw and maize stover is 81.9 Megatonnes (Mt) at field moisture weight (65.3 Mt as dry weight), yielding 470 PJ as gross (404 PJ as net) advanced bioethanol output. Calculated net advanced bioethanol can replace 2.95% of EU transport sector’s energy consumption. EU’s advanced bioethanol has a land footprint of 0.28 m2 MJ−1 for wheat straw and 0.18 m2 MJ−1 for maize stover. The average water footprint of advanced bioethanol is 173 L MJ−1 for wheat straw and 113 L MJ−1 for maize stover. The average carbon footprint per unit of advanced bioethanol is 19.4 and 19.6 g CO2eq MJ−1 for wheat straw and maize stover, respectively. Using advanced bioethanol can lead to emission savings, but EU’s advanced bioethanol production potential is insufficient to achieve EU’s target of a minimum share of 3.5% of advanced biofuels in the transport sector by 2030, and the associated water and land footprints are not smaller than footprints of conventional bioethanol. [ABSTRACT FROM AUTHOR]

In this work, alkaline hydrogen peroxide pretreatment (AHP), at low concentrations of chemical reagents and mild temperature, on sugarcane bagasse was evaluated for production of bioethanol via enzymatic hydrolysis using Cellic® CTec3 from Novozymes® and fermentation using Saccharomyces cerevisiae wild-type strain AR5. Sodium hydroxide NaOH and calcium hydroxide Ca(OH)2 as alkaline reagents were used and combined with hydrogen peroxide (H2O2) as oxidant reagent. AHP pretreatment with NaOH increased cellulose content up to 78% and holocellulose content up to 90%, resulting in 35% more of cellulose and holocellulose contents compared with AHP pretreatment with Ca(OH)2. Results of enzymatic hydrolysis of substrate coming from pretreatment with NaOH achieved high holocellulose-to-reducing sugar yield up to 81% in 7 h of reaction time, 30% higher production than using Ca(OH)2. Besides, for the fermentation process, the necessity and effectiveness of removing remaining solids after enzymatic hydrolysis are not reported in the open literature. Finally, the maximum theoretical yield (95%) was obtained using bothalkaline reagents for the fermentation experiments, producing a maximum ethanol concentration of 39 g/L when AHP pretreatment with NaOH was used, as well the ethanol production balances of 28.9% and 19.1%, were achieved according to the pretreatments with NaOH and Ca(OH)2, respectively. [ABSTRACT FROM AUTHOR]

Cellulosic ethanol has been the most promising second-generation biofuel in terms of raw material availability. The production process mandates efficient removal of lignin followed by a three-step sequential enzymatic conversion of cellulose to glucose. Cellobiase (E.C. 3.2.1.21), a β-glucosidase (BGL), obtained preferably from filamentous fungi catalyzes the final rate limiting step of this reaction, namely, the hydrolysis of cellobiose to glucose. It is therefore the most sought after model for cellulosic enzyme research. Efficient conversion of cellulosic biomass to glucose requires enhanced stability and superior catalysis. This in turn mandates strong producer organism able to secrete a high titer of the enzyme into the extracellular medium, optimized media formulation and improvised technologies for catalysis. Particularly, stabilization of the big cellobiose aggregates remains a significant technological bottleneck in this regard. Large aggregates of cellulosic enzymes are indispensible for industrial scale catalysis; however, these enzymes are prone to spontaneous dissociation by sheer dilution. Conventional immobilization and cross-linking approaches involving glutaraldehyde or entrapment in alginate beads have either proven cost-ineffective or have resulted in retention of poor specific activity for efficient catalysis. Over the last decade, new generation enzyme technologies such as synthetic multi - enzyme cellulosome complex, use of protein stabilizing osmolytes and reducing agents to maximize substrate exposure has opened up new avenues for cross-linker free stabilization and enhanced catalysis. The review is a fresh update of the producer strains, media optimizations and enzyme technologies to boost the production of cellulosic ethanol. [ABSTRACT FROM AUTHOR]

A techno-economic evaluation of a lignocellulosic bioethanol facility that uses acid mine drainage for the pre-treatment of weeping love grass (Eragrostis curvula) was performed. Both separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF) reactor configurations were evaluated. Results were compared to an evaluation of the same process with biomass pre-treated with dilute H 2 SO 4. Capital and operating costs were estimated and a simple economic evaluation was conducted. It was found that all scenarios made a loss except for biomass pre-treated with H 2 SO 4 in the SHF reactor configuration, although the high capital cost resulted in a payback period of 80.7 years, which is unfeasible. SHF was found to produce more ethanol at a lower capital cost than SSF, indicating that it is more economically feasible. Incorporating the remediation of AMD into a simultaneous process could help improve process economics. It is thus recommended that a techno-economic evaluation be conducted on a process that produces bioethanol through SHF and simultaneously remediates AMD. Image 1 • Acid mine drainage (AMD) has become an environmental concern in South Africa. • A flowsheet for bioethanol production (SHF & SSF) with AMD pretreatment was developed. • Estimates of capital/operating costs and revenue were used in economic evaluations. • Low ethanol yield (<58 L/ton biomass), resulted in low revenue making process unfeasible. • SHF was found to be more economical than SSF (higher revenue & lower capital cost). [ABSTRACT FROM AUTHOR]

• A combination of point mutation, mating, adaptation, and haploidization was used. • Sugar uptake and ethanol production were enhanced by adaptive evolution. • Evolved strains had strong tolerance to inhibitors in the pretreated straw slurry. Saccharomyces cerevisiae strain with excellent xylose-fermenting capacity and inhibitor tolerance is crucial for lignocellulosic ethanol production. In this study, a combined strategy including site-directed mutagenesis, mating, evolutionary engineering, and haploidization was applied to obtain strains with ideal xylose fermentabilities. Haploid industrial strain KFG4-6B was engineered to overexpress endogenous xylulokinase (XK) and heterologous native or mutated xylose reductase (XR) and xylitol dehydrogenase (XDH) from Scheffersomyces stipitis. The XR-mutated strain HX57D showed over 12% increase in both xylose consumption rate and ethanol yield compared with the XR-native strain. To improve the xylose uptake, the HX57D-derived diploids were subjected to evolutionary engineering. In comparison with HX57D, evolved diploid Z4X-21-18 achieved 4.5-fold increases in rates of xylose consumption and ethanol production when fermenting xylose. When fermenting mixed sugars, the glucose and xylose uptake rates were 1.4-fold and 8.3-fold, respectively, higher. H18s28, a haploid of Z4X-21-18, enabled a further 10% increase in xylose consumption rate when fermenting xylose only. However, it was inferior to its diploid parent when fermenting mixed sugars. In the presaccharification-simultaneous saccharification and fermentation (P-SSF) of the whole pretreated wheat straw slurry with high contents of multiple inhibitors, Z4X-21-18 produced approximately 42 g/L ethanol with a yield of 0.38 g/g total sugars. [ABSTRACT FROM AUTHOR]

Crop residues' potential for the bioeconomy is often limited well below its full extent to prevent soil organic carbon (SOC) depletion. However, when processed in the bioeconomy, biomass carbon can often be partially recovered in a stabilized degradation-resistant coproduct. This study reviews and interlinks the fundaments between these coproducts' process-dependent characteristics and the use of soil models to predict SOC turnover by replacing fresh crop residues with bioeconomy coproducts after processing. Different modeling approaches to incorporating stabilized organic matter into soils were investigated, as well as the input data requirements of a variety of soil models. Stemming from a revision of over 600 datasets, we synthesized and proposed average conversion coefficients from biomass C to coproduct ( C C ‾) and their inherent recalcitrance in agricultural soils ( C R ‾) for pyrolysis ( C C ‾ : 48 %, C R ‾ : 95 %) and gasification ( C C ‾ : 20 %, C R ‾ : 95 %) biochar, hydrochar ( C C ‾ : 31 %, C R ‾ : 83 %), digestate ( C C ‾ : 36 %, C R ‾ : 68 %) and lignocellulosic bioethanol solid ( C C ‾ : 44 %, C R ‾ : 42 %) and liquid ( C C ‾ : 21 %, C R ‾ : 46 %) coproducts. This review thus represents a stepping-stone towards i) setting the fundaments for adapting soil models to the dynamics between crop residue harvest and return of C under multiple forms and ii) exploring future scenarios involving coproduct return as a strategy to increase the supply of renewable C for the bioeconomy while ensuring the maintenance of SOC stocks. [Display omitted] • Review recalcitrant bioeconomy coproducts from crop residues. • The coproducts studied are biochar, hydrochar, digestate, and bioethanol coproducts. • 21–48 % of the carbon in crop residues is converted into bioeconomy coproducts. • The studied coproducts have a recalcitrant carbon content ranging from 42 % to 95 %. • Eight soil models have considered returning bioeconomy coproducts to soils. [ABSTRACT FROM AUTHOR]

Mexico is one of the largest agricultural producers in Latin America and generates a large amount of agricultural residue. The aim of this study was to establish the usefulness of four of the main Mexican crops (corn, wheat, sugarcane, and Agave) as feedstock for lignocellulosic bioethanol production. The lignocellulosic residue ratio (RR), defined as weight of residue (in tons) per ton of product, was measured by sampling crop fields in 11 geographic regions of Mexico. The chemical composition, assessed by Fourier‐transform infrared spectroscopy (FTIR) and carbon‐13 nuclear magnetic resonance (13C NMR), and structural composition (extractives, cellulose, hemicellulose, and lignin contents), heating value, and metal content of these lignocellulosic residues were measured. Biorefinery locations, and their theoretical bioethanol production, were suggested using the gravity center method and techno‐economic criteria. The highest RR (1.1 ton of straw per ton of grain) was obtained for wheat straw followed by corn (0.8 ton of stover per ton of grain), sugar cane (0.15 ton of bagasse per ton of cane), and Agave (0.2 ton of bagasse per ton of stem). The composition of these biomasses varied significantly depending on the parental material in extractive compounds, lignocellulosic matter, ashes, hemicellulose, lignin, O‐alkyl C, aromatic C, and carboxyl C. The cellulose crystallinity index and the heating value exhibited small variations among biomasses. Copper, Zn, Cd, and Ni content in the biomasses generally exceeded the European Norm (EN‐Plus FprEN 1496 1‐2 B) for solid biofuels. In total, these agricultural biomasses could be used as feedstock for 34 biorefineries in Mexico with a total bioethanol production potential of approximately 1246 million L year–1. © 2019 Society of Chemical Industry and John Wiley & Sons, Ltd [ABSTRACT FROM AUTHOR]

The development of robust microorganisms that can efficiently ferment both glucose and xylose represents one of the major challenges in achieving a cost-effective lignocellulosic bioethanol production. Candida intermedia is a non-conventional, xylose-utilizing yeast species with a high-capacity xylose transport system. The natural ability of C. intermedia to produce ethanol from xylose makes it attractive as a non-GMO alternative for lignocellulosic biomass conversion in biorefineries. We have evaluated the fermentation capacity and the tolerance to lignocellulose-derived inhibitors and the end product, ethanol, of the C. intermedia strain CBS 141442 isolated from steam-exploded wheat straw hydrolysate. In a mixed sugar fermentation medium, C. intermedia CBS 141442 co-fermented glucose and xylose, although with a preference for glucose over xylose. The strain was clearly more sensitive to inhibitors and ethanol when consuming xylose than glucose. C. intermedia CBS 141442 was also subjected to evolutionary engineering with the aim of increasing its tolerance to inhibitors and ethanol, and thus improving its fermentation capacity under harsh conditions. The resulting evolved population was able to ferment a 50% (v/v) steam-exploded wheat straw hydrolysate (which was completely inhibitory to the parental strain), improving the sugar consumption and the final ethanol concentration. The evolved population also exhibited a better tolerance to ethanol when growing in a xylose medium supplemented with 35.5 g/L ethanol. These results highlight the potential of C. intermedia CBS 141442 to become a robust yeast for the conversion of lignocellulose to ethanol. [ABSTRACT FROM AUTHOR]

[Display omitted] • ML models were employed for bioethanol production prediction and optimization. • Over 0.8 accuracy was achieved in predicting ethanol yield and NaOH consumption. • ML models identified optimal conditions, increasing ethanol yield by ∼ 18%. • Integration of ML with LCA showed a ∼ 14% reduction for GHG emission. The availability and accuracy of data play a critical role in the development of Life Cycle Assessment (LCA) models, as they directly impact the effectiveness and reliability of the model. Machine learning (ML) approach has the potential to improve the data quality, leading to enhanced performance of LCA models. In this study, ML algorithms (random forest, extreme gradient boosting, and artificial neural network) were applied to predict the ethanol yield and NaOH consumption, which were key life cycle inventories for lignocellulosic bioethanol process. The prediction models exhibited a decent level of accuracy for ethanol yield (accuracy ∼ 0.85) and NaOH consumption (accuracy > 0.8). In addition, ML algorithms (genetic algorithms, particle swarm optimization, and simulate annealing) were applied to identify optimal feedstock characteristics and conditions for maximum ethanol yield. The optimization models showed an 18% improvement compared to the highest yield from the dataset (0.41 g/g). The ML models (prediction and optimization algorithms) were further integrated with the LCA model (GREET1) to enhance the ethanol yield and to reduce greenhouse gas (GHG) emission for target feedstocks. This resulted in a 6% and 19% improvement in ethanol yield and an approximately 8% and 14% reduction of GHG emissions for grass and corn stover, respectively. This study demonstrates the feasibility of utilizing ML to predict LCA metrics for the development of LCA models and to optimize the process parameters to minimize environmental impact. [ABSTRACT FROM AUTHOR]

The production of cellulosic bioethanol from non-edible plants is receiving increasing attention for its potential to avoid food–fuel competition. However, seasonal variability in feedstock supplies increases the costs of stockpiling and limits commercialization. The cellulosic energy plant Napier grass (Pennisetum purpureum) has conventionally been harvested three times per year (on a 4-month cycle) in Indonesia. To shorten this cycle, we examined an alternative system in which every four rows (rather than the entire crop) were alternately harvested every 2 months (partial harvesting). Results from a 20-month experiment indicated that partial harvesting was effective in shortening the supply cycle from 4 to 2 months. Moreover, partial harvesting significantly increased biomass yield, probably as a result of the border effect. Investigations into available light, atmospheric CO2 concentration, and soil volumetric water content suggested that partial harvesting allowed Napier grass to capture more light for biomass production.

Separation and dehydration process is a key step to reduce the total production cost of lignocellulosic bioethanol. In the earlier work (Torres-Ortega and Rong, 2016), we have obtained new intensified systems for lignocellulosic bioethanol separation and dehydration through dividing wall columns, which have considerable reduction to both capital and energy costs. This work presents the analysis of process features and control properties of the intensified systems with similar capital reduction and energy savings. The control properties were based on singular value decomposition (SVD) and dynamic performances under mild disturbances and changes of set point in Aspen Dynamics V8.8. The control properties and dynamic responses of the intensified separation systems were examined against the reference system for their structural changes during intensification by thermal couplings and column section recombination. The simultaneous analysis of process feature changes by intensification and their control properties achieved the intensified systems with both cost savings and competitive control properties. [ABSTRACT FROM AUTHOR]

The recalcitrant structure of lignocellulosic biomass is a major barrier in efficient biomass-to-ethanol bioconversion processes. The combination of feedstock engineering via modification in the lignin synthesis pathway of sugarcane and co-fermentation of xylose and glucose with a recombinant xylose utilizing yeast strain produced 148% more ethanol compared to that of the wild type biomass and control strain. The lignin reduced biomass led to a substantially increased release of fermentable sugars (glucose and xylose). The engineered yeast strain efficiently co-utilized glucose and xylose for fermentation, elevating ethanol yields. In this study, it was experimentally demonstrated that the combined efforts of engineering both feedstock and microorganisms largely enhances the bioconversion of lignocellulosic feedstock to bioethanol. This strategy will significantly improve the economic feasibility of lignocellulosic biofuels production. [ABSTRACT FROM AUTHOR]

Purpose: The production of cellulase enzymes (CE) has been identified as one major contributor towards the life cycle environmental and economic impacts of second-generation lignocellulosic bioethanol (LCB) production. Despite this knowledge, the literature lacks consistent and transparent life cycle assessments (LCA) which compare CE production based on the three more commonly proposed carbon sources: cornstarch glucose, sugar cane molasses and pre-treated softwood. Furthermore, numerous LCAs of LCB omit CE production from their system boundaries, with several authors citing the lack of available production data. Methods: In this article, we perform a comparative attributional LCA for the on-site production of 1 kg CE in full broth via submerged aerobic fermentation (SmF) based on the three alternative carbon sources, cases A, B and C, respectively. We determine life cycle inventory (LCI) material consumption using stoichiometric equations and volume flow, supplemented with information from the literature. All LCIs are provided in a consistent and transparent manner, filling the existing data gaps towards performing representative LCAs of LCB production with on-site CE production. Life cycle impact assessment (LCIA) results are determined with SimaPro 8 software using CML 1A baseline and non-baseline methods along with cumulative energy demand and are compared to results of similar studies. Sensitivity analysis is performed both for all major assumptions and for market changes with the application of advanced attributional LCA (AALCA). Results and discussion: We find that CE production from pre-treated softwood (case C) provides the lowest environmental impacts, followed by sugar cane molasses (case B) and then cornstarch glucose (case A), with global warming potentials of 7.9, 9.1 and 10.6 kg CO eq./kg enzyme, respectively. These findings compare well with those of similar studies, though great variation exists in the literature. Through sensitivity analysis, we determine that results are sensitive to assumptions made concerning carbon source origin, applied allocation, market changes, process efficiency and electricity supply. Conclusions: Furthermore, we find that the contribution of CE production towards the overall life cycle impacts of LCB is significant and that the omission of this sub-process in LCAs of LCB production can compromise their representativeness. [ABSTRACT FROM AUTHOR]

The effect of non-catalytic protein addition on the adsorption/desorption behavior of individual cellulase components on/from substrates during the hydrolysis of microcrystalline cellulose and steam exploded sugarcane bagasse (SEB) were investigated. The addition of non-catalytic protein enhanced the enzymatic hydrolysis of SEB, but did not enhance the hydrolysis of microcrystalline cellulose. During the hydrolysis of SEB, adsorption of beta-glucosidase (BGL) was prevented in the presence of non-catalytic protein. Cellobiohydrolase I (CBH I) and endoglucanase I (EG I) desorbed from the substrate after temporary adsorption in the presence of non-catalytic protein during SEB hydrolysis. This suggested that reduction of the non-specific adsorption of cellulase components, CBH I, EG I, and BGL, on lignin in SEB led to the improving of enzymatic hydrolysis. [ABSTRACT FROM AUTHOR]

BACKGROUND Brachypodium distachyon (L.) Beauv. is a monocotyledonous model plant that has been studied to understand a range of biological phenomena for lignocellulosic bioethanol feedstocks and other cereal crops. The lignin makes its cell walls recalcitrant to saccharification, constituting the main barrier to lignocellulosic bioethanol production. In this study, lignin-deficient mutants of B. distachyon induced by chronic radiation were selected and the effects of the mutants on fermentable glucose production were identified. RESULTS Brachypodium distachyon M2 mutants induced by chronically irradiated gamma radiation were screened by the Wiesner test. Lignin-deficient M2 mutants were further confirmed in subsequent M3 and M4 generations by determining acetyl bromide-soluble lignin. The lignin content was significantly reduced in mutant plants 135-2 (by 7.99%), 142-3 (by 13.8%) and 406-1 (by 8.13%) compared with the wild type. Moreover, fermentable glucose was significantly higher in 135-2 (by 23.91%) and 142-3 (by 36.72%) than in the wild type after 72 h of enzymatic hydrolysis. CONCLUSION Three lignin-deficient B. distachyon mutants induced by chronically irradiated gamma radiation were obtained. This study will provide fundamental understanding of the B. distachyon cell wall and could contribute to increases in bioethanol production using bioenergy crops. © 2016 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Sugarcane ( Saccharum sp. hybrids) is one of the most efficient and sustainable feedstocks for commercial production of fuel ethanol. Recent efforts focus on the integration of first and second generation bioethanol conversion technologies for sugarcane to increase biofuel yields. This integrated process will utilize both the cell wall bound sugars of the abundant lignocellulosic sugarcane residues in addition to the sucrose from stem internodes. Enzymatic hydrolysis of lignocellulosic biomass into its component sugars requires significant amounts of cell wall degrading enzymes. In planta production of xylanases has the potential to reduce costs associated with enzymatic hydrolysis but has been reported to compromise plant growth and development. To address this problem, we expressed a hyperthermostable GH10 xylanase, xyl10B in transgenic sugarcane which displays optimal catalytic activity at 105 °C and only residual catalytic activity at temperatures below 70 °C. Transgene integration and expression in sugarcane were confirmed by Southern blot, RT-PCR, ELISA and western blot following biolistic co-transfer of minimal expression cassettes of xyl10B and the selectable neomycin phosphotransferase II. Xylanase activity was detected in 17 transgenic lines with a fluorogenic xylanase activity assay. Up to 1.2% of the total soluble protein fraction of vegetative progenies with integration of chloroplast targeted expression represented the recombinant Xyl10B protein. Xyl10B activity was stable in vegetative progenies. Tissues retained 75% of the xylanase activity after drying of leaves at 35 °C and a 2 month storage period. Transgenic sugarcane plants producing Xyl10B did not differ from non-transgenic sugarcane in growth and development under greenhouse conditions. Sugarcane xylan and bagasse were used as substrate for enzymatic hydrolysis with the in planta produced Xyl10B. TLC and HPLC analysis of hydrolysis products confirmed the superior catalytic activity and stability of the in planta produced Xyl10B with xylobiose as a prominent degradation product. These findings will contribute to advancing consolidated processing of lignocellulosic sugarcane biomass. [ABSTRACT FROM AUTHOR]

This study assessed the economic viability of using Miscanthus x giganteus as a feedstock for the production of bioethanol based on plant designs and models by the National Renewable Energy Laboratory. In 2007 dollars, the total cost of installed equipment for a plant with an annual feedstock requirement of 701 million kg/year was $281 million, with the single largest component, cost of feedstock, contributing approximately 40% to the total. The total capital investment needed for the plant was $464 million, or $2.01 per annual liters of ethanol. The variable operating cost of the plant varied between $79 and $93 million per year, depending on the cost of feedstock. The minimum ethanol-selling price (MESP) was calculated from discount cash flow rate analysis. Changing the feedstock cost from $0.08/kg to $0.10/kg increased the MESP from $0.65/L to $0.71/L. The analysis estimated the sensitivity of the MESP to variations in the percentage of equity financing (from 0 to 100%), internal rate of return (from 10% to 20%) and federal corporate taxes (from 30% to 60%). The results of the study allow a direct comparison of the MESP for Miscanthus as opposed to corn-stover, grass straw and hybrid poplar, and provide a benchmark for future studies of economic feasibility of alternative lignocellulosic feedstocks against each other as well as against conventional gasoline and diesel fuels. [ABSTRACT FROM AUTHOR]

Utilization of oil palm empty fruit bunch (OPEFB) for bioethanol production with crude cellulase cocktails from locally isolated fungi was studied. Enzymatic saccharification of alkaline pretreated OPEFB was done using different cellulase enzyme preparations. Crude cellulase cocktails from Trichoderma asperellum UPM1 and Aspergillus fumigatus UPM2 produced 8.37 g/L reducing sugars with 0.17 g/g yield. Production of bioethanol from OPEFB hydrolysate using Baker’s yeast produced approximately 0.59 g/L ethanol, corresponding to 13.8% of the theoretical yield. High reducing sugars concentration in the final fermentation samples resulted from accumulation of non-fermentable sugars such as xylose and cellobiose that were not consumed by the yeast. The results obtained support the possible utilization of OPEFB biomass for bioethanol production in the future.

Bioethanol from sugarcane can be produced using first-generation (1G) or second-generation (2G) technologies. 2G technologies can increase the capacity of production per sugarcane mass input and are expected to have a key role in future reductions of environmental impacts of sugarcane bioethanol. A hybrid Input-Output (IO) framework is developed for Brazil coupling the System of National Accounts and the National Energy Balance, which is extended to assess Greenhouse Gas (GHG) emissions. Life-cycle based estimates for two sugarcane cultivation systems, two 1G and eight 2G bioethanol production scenarios, are coupled in the IO framework. A multi-objective linear programming (MOLP) model is formulated based on this framework for energy-economic-environmental analysis of the Brazilian economic system and domestic bioethanol supply in prospective scenarios. Twenty-four solutions are computed: four “extreme” solutions resulting from the individual optimization of each objective function (GDP, employment level, total energy consumption and total GHG emissions - 1G scenario), ten compromise solutions minimizing the distance of the feasible region to the ideal solution (1G, 1G-optimized and prospective 1G + 2G scenarios), and ten solutions maximizing the total bioethanol production (1G, 1G-optimized and prospective 1G + 2G scenarios). Higher diesel oil and lubricants consumption in the mechanical harvesting process has counterbalanced the positive effects of more efficient trucks leading to higher energy consumption and GHG emissions. Lower overall employment level in the 1G + 2G scenarios is achieved such that policies linked to reabsorption of sugarcane cutters in alternative activities are positive. Indirect effects from maximizing the bioethanol production increase the total energy consumption and the GHG emissions thus requiring efficiency measures and fossil energy substitution by cleaner sources. The integrated- or country-based analysis of the whole economic system has complemented the process design and process-based analysis, contributing to identify direct and indirect effects that can offset the benefits. Direct and indirect effects on the whole economic system have to be considered in policies and technological choices for prospective bioethanol production, since positive direct effects of 1G + 2G plants can be counterbalanced by indirect impacts on other sectors, mainly from chemicals in the process. [ABSTRACT FROM AUTHOR]

Lignocellulosic bioethanol is an important renewable fuel for transportation purpose. Commercial production of lignocellulosic bioethanol mainly depends on cost of cellulase production, efficient pretreatment and enzymatic hydrolysis process. In the present study cellulase production from Aspergillus niger under submerged fermentation (SmF) was optimized using coconut water as natural medium. Maximum cellulase production (0.53 IU/mL) was achieved within 3 days of incubation using 8 % (w/v) waste paper and 0.07 % (w/v) glucose. The produced cellulase was applied for enzymatic hydrolysis of thermo chemically (dilute acid and alkaline) pretreated biomass (equal mixture of wheat straw and cotton stalk). Optimization of dilute acid and dilute alkaline pretreatment showed dilute alkaline pretreatment was more effective for higher reducing sugar production. Maximum reducing sugar yield of 398.0 mg/g dry biomass was obtained from dilute alkaline pretreated biomass (using 0.5 M sodium hydroxide, 8 % substrate concentration, 120 °C temperature and 20 min of incubation time). The presence of difference sugars (glucose, xylose, mannose, maltose) in the saccharified sample was confirmed by thin layer chromatographic analysis. The effectiveness of dilute alkaline pretreatment was further confirmed by biochemical composition (cellulose, hemicelluloses and lignin) and structural (furrier transformed infrared spectroscopic and scanning electron microscopic) analysis. The above result can be useful for commercial production of lignocellulosic bioethanol. [ABSTRACT FROM AUTHOR]

Industrial technologies for bioethanol production from lignocellulosic biomass were reviewed by integrating feedstock handling, selective-fractionation, synergistic enzymatic hydrolysis, industrial fermenting yeast strains, and simultaneous saccharification and co-fermentation in this paper. The breakthrough of integrated technologies contributed to economic feasibility was also analyzed by industrial operation test. With the integrated technologies, the feedstock cost was reduced by 19.4% compared with traditional conversion process. The enzyme loading was reduced by 25.0% using synergistic enzyme systems compared with single cellulase addition. The pre-hydrolysis and simultaneous saccharification and co-fermentation without detoxification operation was developed using inhibitors-tolerant Saccharomyces cerevisiae . More than 4% (w/w) ethanol concentration was achieved, which corresponded to 72.3% theoretical yield of ethanol. The improved conversion efficiency of pentose resulted in 41% increase of ethanol yield. Additionally, lignin plastic composite material (LPCM) and compress natural gas (CNG) were co-produced, which proportioned the capital cost of process and hence facilitated the economic feasibility of process. As a result, the corresponding ethanol total cost was reduced to 5571.6 Yuan/t (Yuan, Chinese currency). In conclusion, the low cost of feedstock, simple and integrated conversion process, and multi-products production contribute to the competiveness of this integrated industrial technology for lignocellulosic bioethanol production. [ABSTRACT FROM AUTHOR]

The objective of this paper is to conduct Life Cycle Assessment (LCA) and Environmental Life Cycle Costing (ELCC) studies for lignocellulosic bioethanol blends [E10 and E85 (10% and 85% by volume of bioethanol with gasoline, respectively)] and conventional gasoline (CG). To compare the environmental performance and economic advantage of the selected fuel blends, the impact potentials and the cost of fuel applications per kilometer by a middle size car was evaluated. According the LCA results, one kilometer driven by E10 and E85 fueled vehicles could reduce the greenhouse gas (GHG) emissions by 4.3% and 47% and ozone layer depletion emissions by 3% and 66%, respectively, relative to CG. However, shifting from gasoline to bioethanol increases the emissions that contribute to eutrophication and photochemical ozone depletion. In terms of acidification potential, E85 shows a more favorable result relative to E10 and CG. According to the ELCC analysis, E85 fuel use provides a 23% lower driving cost relative to CG based on a-1 km driving distance. The results showed that E85 seems to be the best alternative in terms of both GHG emission and fuel production cost reduction compare to CG. [ABSTRACT FROM AUTHOR]

Industrial yeast strains with good xylose fermentation ability and inhibitor tolerance are important for economical lignocellulosic bioethanol production. The flocculating industrial Saccharomyces cerevisiae strain NAPX37, harboring the xylose reductase-xylitol dehydrogenase (XR-XDH)-based xylose metabolic pathway, displayed efficient xylose fermentation during batch and continuous fermentation. During batch fermentation, the xylose consumption rates at the first 36 h were similar (1.37 g/L/h) when the initial xylose concentrations were 50 and 75 g/L, indicating that xylose fermentation was not inhibited even when the xylose concentration was as high as 75 g/L. The presence of glucose, at concentrations of up to 25 g/L, did not affect xylose consumption rate at the first 36 h. Strain NAPX37 showed stable xylose fermentation capacity during continuous ethanol fermentation using xylose as the sole sugar, for almost 1 year. Fermentation remained stable at a dilution rate of 0.05/h, even though the xylose concentration in the feed was as high as 100 g/L. Aeration rate, xylose concentration, and MgSO concentration were found to affect xylose consumption and ethanol yield. When the xylose concentration in the feed was 75 g/L, a high xylose consumption rate of 6.62 g/L/h and an ethanol yield of 0.394 were achieved under an aeration rate of 0.1 vvm, dilution rate of 0.1/h, and 5 mM MgSO. In addition, strain NAPX37 exhibited good tolerance to inhibitors such as weak acids, furans, and phenolics during xylose fermentation. These findings indicate that strain NAPX37 is a promising candidate for application in the industrial production of lignocellulosic bioethanol. [ABSTRACT FROM AUTHOR]

Bringing down energy system emissions to zero is a key step to restrict the global temperature rise to "well below 2 °C". Recent studies have extensively discussed the integration of bioenergy with carbon capture and storage (BECCS) in existing energy systems to achieve net-zero emissions. India recently initiated a carbon dioxide-based enhanced oil recovery (CO 2 -EOR) project in the matured oil wells of western India. Using this project, we propose a bioenergy-CO 2 -EOR system to study the techno-economic feasibility and potential of BECCS towards net-zero emissions from energy systems. We use mixed integer linear programming for bioenergy and CO 2 source-sink matching. The proposed system breaks even, without any carbon price, at an oil price of around 56 USD per barrel (USD/bbl) if using CO 2 from bioethanol fermentation and at around 90 USD/bbl for bioelectricity plants. A carbon price between USD 20 to 40 per tonne of CO 2 makes the system feasible even below the oil price of 45 USD/bbl for the ethanol route. The system has net negative CO 2 emissions after accounting for the lifecycle emissions of produced oil, assuming a sequestration rate of 0.5 tonne of CO 2 per barrel of recovered oil. Further, the bioenergy-CO 2 -EOR system reduces crude oil imports, supports ethanol blending, provides additional income opportunities at local level, and reduces air pollution from crop residue burning in the fields. • We study bioenergy with carbon capture and storage-based enhanced oil recovery. • We use mixed integer linear programming for bioenergy and CO 2 source-sink matching. • The proposed system breaks even at oil price of around USD 56 per barrel. • A carbon price of USD 20–40 could make the system profitable for lower oil prices. • An integrated approach to BECCS is required to sustainably achieve net-zero emissions. [ABSTRACT FROM AUTHOR]

On a near future, bio-based economy will assume a key role in our lives. Lignocellulosic materials (e.g., agroforestry residues, industrial/solid wastes) represent a cheaper and environmentally friendly option to fossil fuels. Indeed, following suitable processing, they can be metabolized by different microorganisms to produce a wide range of compounds currently obtained by chemical synthesis. However, due to the recalcitrant nature of these materials, they cannot be directly used by microorganisms, the conversion of polysaccharides into simpler sugars being thus required. This conversion, which is usually undertaken enzymatically, represents a significant part on the final cost of the process. This fact has driven intense efforts on the reduction of the enzyme cost following different strategies. Here, we describe the fundamentals of the enzyme recycling technology, more specifically, cellulase recycling. We focus on the main strategies available for the recovery of both the liquid- and solid-bound enzyme fractions and discuss the relevant operational parameters (e.g., composition, temperature, additives, and pH). Although the efforts from the industry and enzyme suppliers are primarily oriented toward the development of enzyme cocktails able to quickly and effectively process biomass, it seems clear by now that enzyme recycling is technically possible. [ABSTRACT FROM AUTHOR]

This article examines land-use, market and welfare implications of lignocellulosic bioethanol production in Hawai'i to satisfy 10% and 20% of the State's gasoline demand in line with the State's ethanol blending mandate and Alternative Fuels Standard (AFS). A static computable general equilibrium (CGE) model is used to evaluate four alternative support mechanisms for bioethanol. Namely: i) a federal blending tax credit, ii) a long-term purchase contract, iii) a state production subsidy financed by a lump-sum tax and iv) a state production subsidy financed by an ad valorem gasoline tax. We find that because Hawaii-produced bioethanol is relatively costly, all scenarios are welfare reducing for Hawaii residents: estimated between −0.14% and −0.32%. Unsurprisingly, Hawaii's economy and its residents fair best under the federal blending tax credit scenario, with a positive impact to gross state product of $49 million. Otherwise, impacts to gross state product are negative (up to −$63 million). We additionally find that Hawaii-based bioethanol is not likely to offer substantial greenhouse gas emissions savings in comparison to imported biofuel, and as such the policy cost per tonne of emissions displaced ranges between $130 and $2100/tonne of CO 2 e. The policies serve to increase the value of agricultural lands, where we estimate that the value of pasture land could as well. [ABSTRACT FROM AUTHOR]

A high number of life cycle assessment of the production of lignocellulosic bioethanol have been published to evaluate or to demonstrate its environmental benefits, in most of the cases the comparison of results and conclusions is difficult due the different methodological approaches of the analysts. The aim of this review is to synthesize and to analyze the available and updated information concerning to life cycle assessment (LCA) of lignocellulosic bioethanol and to compare its environmental impacts with conventional fossil fuels and the first-generation bioethanol. This review analyzes more than one hundred case studies reported in the last decade, whose main focus were the energy balance and the green house gas (GHG) emissions, considering the methods of analysis, assumptions and the most used impact categories. The studies showed a clear reduction in GHG emissions and ozone layer depletion, while results in other impact categories, such as acidification, eutrophication, human health and photochemical smog showed to be positively or negatively affected. The LCA results of the bioethanol production are highly influenced by the bioethanol proportion in the gasoline–bioethanol blend and by the source of raw material: GHG emissions reduction is less than 10% for E10 blend and higher than 40% for E85 and upper blends. When comparing raw materials for E100 blend, the highest GHG reduction per distance traveled were obtained for agricultural residues, with reductions between 82 and 91%. In the case of switchgrass and wood, the reduction values were between 53–93% and 50–62%, respectively. Most of the reviewed studies found that lignocellulosic bioethanol production is energetically sustainable, being this result dependent on the possibility of using by-products as fuel in a cogeneration system. It has been shown that lignocellulosic bioethanol have lower impacts in most of the categories and a positive energy balance compared with first generation bioethanol and gasoline. [ABSTRACT FROM AUTHOR]

Bioethanol from lignocellulose is an attractive alternative to fossil fuels, and Saccharomyces cerevisiae is the most important ethanol producer. However, yeast cells are challenged by various environmental stresses during ethanol production on an industrial scale, and robust strains with a high tolerance to inhibitors, temperature and osmolality are needed for the effective feasibility of lignocellulosic ethanol. To search for such innately more resistant yeast, we selected grape marc as an extreme environment due to limited nutrients, exposure to solar radiation, temperature fluctuations, weak acids and ethanol. Using a temperature of 40 °C as the key selection criterion, we isolated 120 novel S. cerevisiae strains from grape marc and found high ethanol yields (up to 92 % of the theoretical maximum) when inoculated at 40 °C in minimal media with a high sugar concentration. For the first time, this work assessed yeast tolerance to inhibitors at 40 °C, and the newly isolated yeast strains displayed interesting abilities to withstand increasing levels of single inhibitors or cocktails containing a mixture of inhibitory compounds. The newly isolated strains showed significantly higher fermentative abilities and tolerance to inhibitors than the industrial and commercial benchmark S. cerevisiae strains. The strong physiological robustness and fitness of a few of these S. cerevisiae yeast strains support their potential industrial application and encourage further studies in genetic engineering to enhance their ethanol performance in terms of rate and yield through the co-fermentation of all available carbon sources. [ABSTRACT FROM AUTHOR]

A CO-added ammonia explosion pretreatment was performed for bioethanol production from rice straw. The pretreatment conditions, such as ammonia concentration, CO loading level, residence time, and temperature were optimized using response surface methodology. The response for optimization was defined as the glucose conversion rate. The optimized pretreatment conditions resulting in maximal glucose yield (93.6 %) were determined as 14.3 % of ammonia concentration, 2.2 MPa of CO loading level, 165.1 °C of temperature, and 69.8 min of residence time. Scanning electron microscopy analysis showed that pretreatment of rice straw strongly increased the surface area and pore size, thus increasing enzymatic accessibility for enzymatic saccharification. Finally, an ethanol yield of 97 % was achieved via simultaneous saccharification and fermentation. Thus, the present study suggests that CO-added ammonia pretreatment is an appropriate process for bioethanol production from rice straw. [ABSTRACT FROM AUTHOR]

Highlights: [•] Oil palm Empty Fruit Bunches shown as good candidates for bioethanol production. [•] Two pretreatment techniques compared (acid/alkali): the first option is superior. [•] Optimized dilute acid treatment (≈161°C, 10min, 1.5% acid): 85% glucose yield. [•] Alkali treatment is seriously hampered by high lignin content of the feedstock. [•] Fate of the different components of biomass monitored during each treatment. [ABSTRACT FROM AUTHOR]

SUMMARY Energy demand is increasing by the years. Population's needs and technological investments bring the new approach about generating energy. It is considered that fossil fuels will not be able to respond to all energy requirements after approximately 150 years. Turkey imports nearly all of its petroleum and so this causes major economic problems. Turkey, as a major cereal producer, has a huge potential to grow energy crops and other cellulosic biomaterials and can obtain plant's residues, which are suitable to produce second generation bioethanol (SGB). With domestic production, bioethanol can reduce the dependence of petroleum for Turkey, and greenhouse gas emissions can be decreased. Taking into account Turkey's situation in fuel-oil consumption, costliness of gasoline and environmentally hazardous specification of fossil fuels, bioethanol gains more importance and increases in value. Especially, SGB production is rising. Foodstuffs are valuable, and producing ethanol from directly those materials can cause a crisis in Turkey because lignocellulosic bioethanol is becoming prominent. In this regard, bioethanol production in Turkey becomes a major alternative to petroleum and may be a key to new and clean energy source. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Measurement of the protein content in samples from production of lignocellulosic bioethanol is an important tool when studying the adsorption of cellulases. Several methods have been used for this, and after reviewing the literature, we concluded that one of the most promising assays for simple and fast protein measurement on this type of samples was the ninhydrin assay. This method has also been used widely for this purpose, but with two different methods for protein hydrolysis prior to the assay-alkaline or acidic hydrolysis. In samples containing glucose or ethanol, there was significant interference from these compounds when using acid hydrolysis, which was not the case when using the alkaline hydrolysis. We evaluated the interference from glucose, cellulose, xylose, xylan, lignin and ethanol on protein determination of BSA, Accellerase® 1500 and Cellic® CTec2. The experiments demonstrated that the presence of cellulose, lignin and glucose (above 50 g/kg) could significantly affect the results of the assay. Comparison of analyses performed with the ninhydrin assay and with a CN analyser revealed that there was good agreement between these two analytical methods, but care has to be taken when applying the ninhydrin assay. If used correctly, the ninhydrin assay can be used as a fast method to evaluate the adsorption of cellulases to lignin. [ABSTRACT FROM AUTHOR]

Background Enzyme recycling is a method to reduce the production costs for advanced bioethanol by lowering the overall use of enzymes. Commercial cellulase preparations consist of many different enzymes that are important for efficient and complete cellulose (and hemicellulose) hydrolysis. This abundance of different activities complicates enzyme recycling since the individual enzymes behave differently in the process. Previously, the general perception was that β-glucosidases could easily be recycled via the liquid phase, as they have mostly been observed not to adsorb to pretreated biomass or only adsorb to a minor extent. Results The results from this study with Cellic® CTec2 revealed that the vast majority of the β- glucosidase activity was lost from the liquid phase and was adsorbed to the residual biomass during hydrolysis and fermentation. Adsorption studies with β-glucosidases in two commercial preparations (Novozym 188 and Cellic® CTec2) to substrates mimicking the components in pretreated wheat straw revealed that the Aspergillus niger β-glucosidase in Novozym 188 did not adsorb significantly to any of the components in pretreated wheat straw, whereas the β-glucosidase in Cellic® CTec2 adsorbed strongly to lignin. The extent of adsorption of β-glucosidase from Cellic® CTec2 was affected by both type of biomass and pretreatment method. With approximately 65% of the β-glucosidases from Cellic® CTec2 adsorbed onto lignin from pretreated wheat straw, the activity of the β- glucosidases in the slurry decreased by only 15%. This demonstrated that some enzyme remained active despite being bound. It was possible to reduce the adsorption of Cellic® CTec2 β-glucosidase to lignin from pretreated wheat straw by addition of bovine serum albumin or poly(ethylene glycol). Conclusions Contrary to the β-glucosidases in Novozym 188, the β-glucosidases in Cellic® CTec2 adsorb significantly to lignin. The lignin adsorption observed for Cellic® CTec2 is usually not a problem during hydrolysis and fermentation since most of the catalytic activity is retained. However, adsorption of β-glucosidases to lignin may prove to be a problem when trying to recycle enzymes in the production of advanced bioethanol. [ABSTRACT FROM AUTHOR]