Search

The efficient biosynthesis is important for the sustainable development of lignocellulosic ethanol industry, but it is limited by furfural stress produced with cellulose pretreatment. Collagen peptide (CP), as an affluent protein resource, considerably improved the tolerance of Saccharomyces cerevisiae against furfural stress. When the furfural concentration was 2 g/L, the residual sugar concentration was reduced from 122.39 to 8.90 g/L, and the final ethanol yield increased from 30.69 to 87.27 g/L in the presence of CP. In addition, the ethanol yield in CP containing media was higher than those in other peptides. Transcriptome analysis showed CP can improve the expression of genes (FBA1, PDC1, PDC6, and ENO1) associated with glycolysis to promote sugar utilization, and enhance ethanol biosynthesis under furfural stress, which were further verified by quantitative real-time PCR. These results indicated that CP is a promising protectant and accelerator for bioethanol biosynthesis. [ABSTRACT FROM AUTHOR]

The sorghum × sudangrass hybrid is significant as a biofuel crop due to its high biomass production, drought tolerance, adaption ability to various climatic conditions, and high sugar content in its stems. This study aimed to determine the effects of six different nitrogen dose treatments on ethanol yield, yield parameters, and fertilizer use relationships in sorghum × sudangrass hybrid plants in two locations in 2021 and 2022. The experiment was established according to the randomized block design with three replicates. Nitrogen treatments were applied as N0 (0 kg da-1), N5 (5 kg da-1), N10 (10 kg da-1), N15 (15 kg da-1), N20 (20 kg da-1), and N25 (25 kg da-1). Juice ethanol yield (JEY), lignocellulosic ethanol yield (LEY), and theoretical ethanol yield (TEY) values varied between 123.8-219.0 L da-1, 522.2-955.1 L da-1, and 646.0-1174.2 L da-1, respectively. JEY, LEY, and TEY values increased as the amount of nitrogen increased. The correlation analysis found a high positive relationship between all traits except acid detergent lignin. As a result of the orthogonal comparison, it was found that the nitrogen dose amount should be increased for JEY, LEY, and TEY. Principal components-biplot analyses explained 92.9% of the relationships between the studied parameters and the nitrogen dose levels. This study, conducted over two years and in two locations, determined that sorghum x sudangrass hybrid cultivation could be realized in terms of bioethanol yield under different nitrogen dose levels and that the ethanol yield potential is high. [ABSTRACT FROM AUTHOR]

The utilization of lignocellulosic materials for second-generation ethanol production via enzymatic catalysts is primarily hindered by enzyme cost. Enzymatic immobilization emerges as a viable solution, enabling enzyme reuse. This study investigated the immobilization of an enzymatic extract obtained from Moniliophthora perniciosa fermentation in calcium alginate spheres using the direct trapping method. Initial tests assessed β-glucosidase activity, showing that a higher concentration of calcium chloride (1 M) alongside larger diameter spheres yielded improved results. The immobilized enzyme was reused for up to 17 cycles without significant loss of activity. The percentage of reducing sugars after 48-h hydrolysis with the supplemented enzymatic extract was 226%, doubling the value achieved with only the free enzymatic extract. The immobilized enzyme retained 50% of its initial activity after 1 h at 80 °C, demonstrating higher activity at pH 6 and 60 °C. These findings suggest that this immobilization technique is simple, economically viable, and effective for the hydrolysis of pretreated sugarcane bagasse. Successful immobilization of M. perniciosa enzymatic extract achieved through direct entrapment in calcium alginate. Immobilized β-glucosidase demonstrates sustained activity over 16 reuse cycles, showcasing the potential for cost-effective bioconversion processes. Enhanced hydrolysis of sugarcane bagasse observed with immobilized enzymatic extract, indicating a promising approach for improved biomass utilization. [ABSTRACT FROM AUTHOR]

In this work, machine learning (ML) applications in lignocellulosic bioethanol production were reviewed. First, the pretreatment-hydrolysis-fermentation route, the most commonly studied alternative, was summarized. Next, a bibliometric analysis was performed to identify the current trends in the field; it was found that ML applications in the field are not only increasing but also expanding their relative share in publications, with bioethanol seeming to be the most frequently researched topic while biochar and biogas are also receiving increased attention in recent years. Then, the implementation of ML for lignocellulosic bioethanol production via this route was reviewed in depth. It was observed that artificial neural network (ANN) is the most commonly used algorithm (appeared in almost 90% of articles), followed by response surface methodology (RSM) (in about 25% of articles) and random forest (RF) (in about 10% of articles). Bioethanol concentration is the most common output variable in the fermentation step, while fermentable sugar and glucose concentration are studied most in hydrolysis. The datasets are usually small, while the fitnesses of the models (R2) are usually high in the papers reviewed. Finally, a perspective for future studies, mostly considering improving data availability, was provided.

In recent years, the cultivation of hemp for seed has been gaining significant importance. Intensive breeding work resulted in the registration of a new oilseed hemp variety with high seed yield called Henola. Hemp of this variety is characterized by a vegetation period shorter by about a month, almost twice shorter technical length of plants and significantly larger inflorescences than fibrous hemp of the standard variety (Białobrzeskie). This work analyzes the efficiency of the second-generation bioethanol production process derived from the processing of waste biomass remaining after deseeding the panicles of the Henola variety. The research material consisted of biomass samples obtained from three variants of the fertilization experiment carried out at the IWNiRZ Experimental Farm in Stary Sielec in temperate climate conditions. In order to find out about the properties of the raw material, the chemical composition of hemp straw was tested and the bioethanol yield per 1 ha of crops was determined. Henola oilseed hemp straw yield was the lowest (10.6 Mg∙ha−1) in the case of the control and the highest (11.3 Mg∙ha−1) with the use of complex phosphorus, potassium and nitrogen fertilization. The average content of cellulose in the analyzed samples was 35.5%, holocellulose 68%, and hemicellulose 32%. The amount of lignin, in turn, was independent of the type of fertilization. The lowest bioethanol content, in the amount 7.11 g∙L−1, was found in case of hemp fertilized with nitrogen, phosphorus and potassium, and the highest content amounting to 9.93 g∙L−1 – for hemp fertilized with phosphorus and potassium, for which the ethanol yield, converted into straw yield was 2.7 m3∙ha−1. The conducted research covers both the identification of pro-environmental solutions in the economy for the management of waste biomass and the implementation of the RED II Directive on the promotion of energy from renewable sources.

In this work, machine learning (ML) applications in lignocellulosic bioethanol production were reviewed. First, the pretreatmenthydrolysis-fermentation route, the most commonly studied alternative, was summarized. Next, a bibliometric analysis was performed to identify the current trends in the field; it was found that ML applications in the field are not only increasing but also expanding their relative share in publications, with bioethanol seeming to be the most frequently researched topic while biochar and biogas are also receiving increased attention in recent years. Then, the implementation of ML for lignocellulosic bioethanol production via this route was reviewed in depth. It was observed that artificial neural network (ANN) is the most commonly used algorithm (appeared in almost 90% of articles), followed by response surface methodology (RSM) (in about 25% of articles) and random forest (RF) (in about 10% of articles). Bioethanol concentration is the most common output variable in the fermentation step, while fermentable sugar and glucose concentration are studied most in hydrolysis. The datasets are usually small, while the fitnesses of the models (R2) are usually high in the papers reviewed. Finally, a perspective for future studies, mostly considering improving data availability, was provided. [ABSTRACT FROM AUTHOR]

Bioethanol produced from agro-residue provides a sustainable alternative to fossil fuels, mitigating pollution, reducing waste, and promoting a circular economy. However, challenges arise in sustainable sourcing, resource conflicts, water quality concerns, and managing environmental footprints to maximize agro-residue-based bioethanol benefits. The environmental impacts, net energy ratio (NER), net energy value, water footprint, and uncertainties associated with bioethanol production from agro-residues are analyzed in this study. The analysis followed a cradle-to-gate approach using 1 L of bioethanol produced as a functional unit (FU), allowing for a direct comparison of the environmental performance of the different feedstocks. The result shows that rice straw-based bioethanol exhibited higher environmental impacts, particularly in terms of ecotoxicity, ionizing radiation, human toxicity, and ozone layer depletion, except for greenhouse gas emission, which is lowest for corn stover (0.37 kg CO 2 eq. per FU) and highest for cassava straw (1.1 kg CO 2 eq. per FU). Furthermore, the Cumulative Energy Demand analysis highlighted a significant reliance on fossil fuels from agricultural biomass throughout the bioethanol production process. The energy balance analysis shows that the agricultural residues are feasible for bioethanol production with NER of 1.20, 3.10, and 3.28 for rice straw, corn stover, and cassava straw, respectively. To enhance the accuracy and reliability of the LCA results, Monte Carlo simulation was employed to account for uncertainty and variability in the data. This methodology provides a better understanding of the impacts of bioethanol production, with a focus on sustainability and advancements in reducing our reliance on fossil fuels. [Display omitted] • Environmental impacts of agricultural residue-based bioethanol are evaluated. • Rice straw bioethanol has high impacts except in greenhouse gas emissions. • Bioethanol production relies significantly on fossil fuels. • Cumulative energy demand and Water footprint analysis was carried out. • Monte Carlo simulations enhance the LCA by accounting for data uncertainty. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Natural Fibers is the property of Taylor & Francis Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The thermochemical/oxidative pretreatment of date palm fibers (DPF) was investigated aiming to enhance bioethanol production from the pretreated biomass. The chemical reagents used were sodium hydroxide and/or hydrogen peroxide in dilute aquatic solutions, to which DPF was subjected at a two-step or one-step process. The effect of the pretreatment was evaluated by estimating the direct removal efficiency of lignin and the solubilization of holocellose, as well as by assessing the induced structural and morphological changes via IR spectroscopy and SEM imaging. Based on the results, a two-step combined pretreatment with NaOH applied first was selected as the most efficient and its effect on the enzymatic digestibility of DPF using commercial cellulolytic enzymes was further studied. Subsequently, batch experiments with the whole pretreated DPF slurries and after separating the solids from the hydrolysate were conducted through simultaneous saccharification and fermentation (SSF) and also separate hydrolysis and fermentation (SHF), using the non-conventional yeasts Pichia anomala (Wicherhamomyces anomalus, strain X19) and Pichia stipitis, either separately or in co-culture. The co-culture yielded to higher ethanol for both slurries and solids, whereas the results obtained from SSF and SHF experiments did not seem to differentiate significantly. The maximum ethanol yield obtained was approximately 150 g/kg dry DPF biomass, indicating that DPF can be a promising feedstock for lignocellulosic ethanol production. [ABSTRACT FROM AUTHOR]

Ethanol is a promising biofuel that can replace fossil fuel, mitigate greenhouse gas (GHG) emissions, and represent a renewable building block for biochemical production. Ethanol can be produced from various feedstocks. First-generation ethanol is mainly produced from sugar- and starch-containing feedstocks. For second-generation ethanol, lignocellulosic biomass is used as a feedstock. Typically, ethanol production contains four major steps, including the conversion of feedstock, fermentation, ethanol recovery, and ethanol storage. Each feedstock requires different procedures for its conversion to fermentable sugar. Lignocellulosic biomass requires extra pretreatment compared to sugar and starch feedstocks to disrupt the structure and improve enzymatic hydrolysis efficiency. Many pretreatment methods are available such as physical, chemical, physicochemical, and biological methods. However, the greatest concern regarding the pretreatment process is inhibitor formation, which might retard enzymatic hydrolysis and fermentation. The main inhibitors are furan derivatives, aromatic compounds, and organic acids. Actions to minimize the effects of inhibitors, detoxification, changing fermentation strategies, and metabolic engineering can subsequently be conducted. In addition to the inhibitors from pretreatment, chemicals used during the pretreatment and fermentation of byproducts may remain in the final product if they are not removed by ethanol distillation and dehydration. Maintaining the quality of ethanol during storage is another concerning issue. Initial impurities of ethanol being stored and its nature, including hygroscopic, high oxygen and carbon dioxide solubility, influence chemical reactions during the storage period and change ethanol's characteristics (e.g., water content, ethanol content, acidity, pH, and electrical conductivity). During ethanol storage periods, nitrogen blanketing and corrosion inhibitors can be applied to reduce the quality degradation rate, the selection of which depends on several factors, such as cost and storage duration. This review article sheds light on the techniques of control used in ethanol fuel production, and also includes specific guidelines to control ethanol quality during production and the storage period in order to preserve ethanol production from first-generation to second-generation feedstock. Finally, the understanding of impurity/inhibitor formation and controlled strategies is crucial. These need to be considered when driving higher ethanol blending mandates in the short term, utilizing ethanol as a renewable building block for chemicals, or adopting ethanol as a hydrogen carrier for the long-term future, as has been recommended. [ABSTRACT FROM AUTHOR]

Abstract Background Consolidated bioprocessing, which combines saccharolytic and fermentative abilities in a single microorganism, is receiving increased attention to decrease environmental and economic costs in lignocellulosic biorefineries. Nevertheless, the economic viability of lignocellulosic ethanol is also dependent of an efficient utilization of the hemicellulosic fraction, which contains xylose as a major component in concentrations that can reach up to 40% of the total biomass in hardwoods and agricultural residues. This major bottleneck is mainly due to the necessity of chemical/enzymatic treatments to hydrolyze hemicellulose into fermentable sugars and to the fact that xylose is not readily consumed by Saccharomyces cerevisiae—the most used organism for large-scale ethanol production. In this work, industrial S. cerevisiae strains, presenting robust traits such as thermotolerance and improved resistance to inhibitors, were evaluated as hosts for the cell-surface display of hemicellulolytic enzymes and optimized xylose assimilation, aiming at the development of whole-cell biocatalysts for consolidated bioprocessing of corn cob-derived hemicellulose. Results These modifications allowed the direct production of ethanol from non-detoxified hemicellulosic liquor obtained by hydrothermal pretreatment of corn cob, reaching an ethanol titer of 11.1 g/L corresponding to a yield of 0.328 g/g of potential xylose and glucose, without the need for external hydrolytic catalysts. Also, consolidated bioprocessing of pretreated corn cob was found to be more efficient for hemicellulosic ethanol production than simultaneous saccharification and fermentation with addition of commercial hemicellulases. Conclusions These results show the potential of industrial S. cerevisiae strains for the design of whole-cell biocatalysts and paves the way for the development of more efficient consolidated bioprocesses for lignocellulosic biomass valorization, further decreasing environmental and economic costs.

The engineering of xylo-oligosaccharide-consuming Saccharomyces cerevisiae strains is a promising approach for more effective utilization of lignocellulosic biomass and the development of economic industrial fermentation processes. Extending the sugar consumption range without catabolite repression by including the metabolism of oligomers instead of only monomers would significantly improve second-generation ethanol production This review focuses on different aspects of the action mechanisms of xylan-degrading enzymes from bacteria and fungi, and their insertion in S. cerevisiae strains to obtain microbial cell factories able of consume these complex sugars and convert them to ethanol. Emphasis is given to different strategies for ethanol production from both extracellular and intracellular xylo-oligosaccharide utilization by S. cerevisiae strains. The suitability of S. cerevisiae for ethanol production combined with its genetic tractability indicates that it can play an important role in xylan bioconversion through the heterologous expression of xylanases from other microorganisms.

Efficient ethanol production using dilute acid pretreated rice straw was investigated in multiple-fed simultaneous saccharification and co-fermentation (mf-SSCF) for producing high titer ethanol at a low cost. The mf-SSCF was performed at very high solid loading (29.5% w/v) by multiple feeding of dilute acid pretreated rice straw without any detoxification, solid-liquid separation, and sterilization. After 72 h, an ethanol titer of 68.72 g L−1 was attained with higher ethanol yield (0.42 g g−1) and productivity (0.95 g L−1 h−1). Only magnesium sulfate (6 g L−1) was added as nutrient component and aqueous ammonia was used for pH adjustment of pretreated slurry to 5, which also provides ammonium ions as a nitrogen source for yeast during ethanol fermentation. Almost no water was added in the mf-SSCF process; therefore, higher ethanol titer (8.7 % v/v) was achieved, which further reduce distillation, water input, and treatment cost. These results suggest that the mf-SSCF process has great potential for the production of high titer ethanol on a commercial scale due to the consolidation and simplification of the process at a low cost. • Pretreated biomass used without detoxification and sterilization. • Aqueous ammonia plays a dual role: pH adjuster and nitrogen source. • Only MgSO 4 supplemented as nutrient. • Almost no water addition in the process after pretreatment. • High titer, yield, and productivity of 2G ethanol at lower CAPEX and OPEX. [ABSTRACT FROM AUTHOR]

Abstract Background Phenolic acids are lignin-derived fermentation inhibitors formed during many pretreatment processes of lignocellulosic biomass. In this study, vanillic, p-hydroxybenzoic, and syringic acids were selected as the model compounds of phenolic acids, and the effect of short-term adaptation strategies on the tolerance of S. cerevisiae to phenolic acids was investigated. The mechanism of phenolic acids tolerance in the adapted yeast strains was studied at the morphological and physiological levels. Results The multiple phenolic acids exerted the synergistic inhibitory effect on the yeast cell growth. In particular, a significant interaction between vanillic and hydroxybenzoic acids was found. The optimal short-term adaptation strategies could efficiently improve the growth and fermentation performance of the yeast strain not only in the synthetic media with phenolic acids, but also in the simultaneous saccharification and ethanol fermentation of corncob residue. Morphological analysis showed that phenolic acids caused the parental strain to generate many cytoplasmic membrane invaginations with crack at the top of these sites and some mitochondria gathered around. The adapted strain presented the thicker cell wall and membrane and smaller cell size than those of the parental strain. In particular, the cytoplasmic membrane generated many little protrusions with regular shape. The cytoplasmic membrane integrity was analyzed by testing the relative electrical conductivity, leakage of intracellular substance, and permeation of fluorescent probe. The results indicated that the short-term adaptation improved the membrane integrity of yeast cell. Conclusion The inhibition mechanism of phenolic acid might be attributed to the combined effect of the cytoplasmic membrane damage and the intracellular acidification. The short-term adaptation strategy with varied stressors levels and adaptive processes accelerated the stress response of yeast cell structure to tolerate phenolic acids. This strategy will contribute to the development of robust microbials for biofuel production from lignocellulosic biomass.

Abstract Bioethanol production processes with Saccharomyces cerevisiae using lignocellulosic biomass as feedstock are challenged by the simultaneous utilization of pentose and hexose sugars from biomass hydrolysates. The pentose uptake into the cell represents a crucial role for the efficiency of the process. The focus of the here presented study was to understand the uptake and conversion of the pentose l-arabinose in S. cerevisiae and reveal its regulation by d-glucose and d-galactose. Gal2p—the most prominent transporter enabling l-arabinose uptake in S. cerevisiae wild-type strains—has an affinity for the transport of l-arabinose, d-glucose, and d-galactose. d-Galactose was reported for being mandatory for inducing GAL2 expression. GAL2 expression is also known to be regulated by d-glucose-mediated carbon catabolite repression, as well as catabolite inactivation. The results of the present study demonstrate that l-arabinose can be used as sole carbon and energy source by the recombinant industrial strain S. cerevisiae DS61180. RT-qPCR and RNA-Seq experiments confirmed that l-arabinose can trigger its own uptake via the induction of GAL2 expression. Expression levels of GAL2 during growth on l-arabinose reached up to 21% of those obtained with d-galactose as sole carbon and energy source. l-Arabinose-induced GAL2 expression was also subject to catabolite repression by d-glucose. Kinetic investigations of substrate uptake, biomass, and product formation during growth on a mixture of d-glucose/l-arabinose revealed impairment of growth and ethanol production from l-arabinose upon d-glucose depletion. The presence of d-glucose is thus preventing the fermentation of l-arabinose in S. cerevisiae DS61180. Comparative transcriptome studies including the wild-type and a precursor strain delivered hints for an increased demand in ATP production and cofactor regeneration during growth of S. cerevisiae DS61180 on l-arabinose. Our results thus emphasize that cofactor and energy metabolism demand attention if the combined conversion of hexose and pentose sugars is intended, for example in biorefineries using lignocellulosics.

Operating lignocellulosic fermentation processes to produce fuels and chemicals is challenging due to the inherent complexity and variability of the fermentation media. Real‐time monitoring is necessary to compensate for these challenges, but the traditional process monitoring methods fail to deliver actionable information that can be used to implement advanced control strategies. In this study, a hybrid‐modeling approach is presented to monitor cellulose‐to‐ethanol (EtOH) fermentations in real‐time. The hybrid approach uses a continuous‐discrete extended Kalman filter to reconciliate the predictions of a data‐driven model and a kinetic model and to estimate the concentration of glucose (Glu), xylose (Xyl), and EtOH. The data‐driven model is based on partial least squares (PLS) regression and predicts in real‐time the concentration of Glu, Xyl, and EtOH from spectra collected with attenuated total reflectance mid‐infrared spectroscopy. The estimations made by the hybrid approach, the data‐driven models and the internal model were compared in two validation experiments showing that the hybrid model significantly outperformed the PLS and improved the predictions of the internal model. Furthermore, the hybrid model delivered consistent estimates even when disturbances in the measurements occurred, demonstrating the robustness of the method. The consistency of the proposed hybrid model opens the doors towards the implementation of advanced feedback control schemes. [ABSTRACT FROM AUTHOR]

Lignocellulosic ethanol production at high temperature offers advantages such as the decrease of contamination risk and cooling cost. Recombinant xylose-fermenting Saccharomyces cerevisiae has been considered a promising strain for ethanol production from lignocellulose for its high inhibitor tolerance and superior capability to ferment glucose and xylose into ethanol. To improve the ethanolic fermentation by xylose at high temperature, the strain YY5A was subjected to the ethyl methanesulfonate (EMS) mutagenesis. A mutant strain T5 was selected from the EMS-treated cultures to produce ethanol. However, the xylose uptake by T5 was severely inhibited by the high ethanol concentration during the cofermentation in defined YPDX medium at 40 °C. In this study, the simultaneous saccharification and co-fermentation (SSCF) and the separate hydrolysis and co-fermentation (SHCF) processes of sugarcane bagasse were assessed to solve this problem. The xylose utilization by T5 was remarkably improved using the SSCF process compared to the SHCF process. For the SHCF and SSCF processes, 48% and 99% of the xylose in the hydrolysate was consumed at 40 °C, respectively. The ethanol yield was enhanced by the SSCF process. The ethanol production can reach to 36.0 g/L using this process under high-temperature conditions. [ABSTRACT FROM AUTHOR]

Solid-state fermentation, featured by water-saving, eco-friendly and high concentration product, is a promising technology in lignocellulosic ethanol industry. However, in solid-state fermentation system, large gas content inside the substrate directly leads to high oxygen partial pressure and inhibits ethanol fermentation. Z. mobilis can produce ethanol from glucose near the theoretical maximum value, but this ethanol yield would be greatly decreased by high oxygen partial pressure during solid-state fermentation. In this study, we applied N2 periodic pulsation process intensification (NPPPI) to ethanol solid-state fermentation, which displaced air with N2 and provided a proper anaerobic environment for Z. mobilis. Based on the water state distribution, the promotion effects of NPPPI on low solid loading and solid-state fermentation were analyzed to confirm the different degrees of oxygen inhibition in ethanol solid-state fermentation. During the simultaneous saccharification solid-state fermentation, the NPPPI group achieved 45.29% ethanol yield improvement and 30.38% concentration improvement compared with the control group. NPPPI also effectively decreased 58.47% of glycerol and 84.24% of acetic acid production and increased the biomass of Z. mobilis. By coupling the peristaltic enzymatic hydrolysis and fed-batch culture, NPPPI made the ethanol yield and concentration reach 80.11% and 55.06 g/L, respectively, in solid-state fermentation. [ABSTRACT FROM AUTHOR]

Yeast productivity in lignocellulosic ethanol fermentation is clearly impeded by stress. Enhancing the robustness of xylose-fermenting yeast is important for improving lignocellulosic ethanol production. In this study, the glutathione biosynthesis pathway and acetic acid degradation pathway were strengthened to enhance yeast tolerance to stress due to elevated reactive oxygen species (ROS) and acetic acid. Dynamic feedback regulation of the anti-stress genetic circuits was achieved using stress-driven promoters discovered from the transcriptome to maintain low intracellular ROS, relieve the metabolic burden, and ultimately improve the robustness and ethanol production of yeast. The cell growth, xylose utilization and ethanol production of the engineered strain were enhanced under both stress and nonstress conditions. The engineered strain showed 49.5% and 17.5% higher ethanol productivity in laboratory media and industrial lignocellulosic media, respectively, at 36 °C compared with the parent strain. This study provides novel insights on the rational design and construction of feedback genetic circuits for dynamically improving yeast robustness. Image 1 • Stress-driven promoters in yeast were mined from transcriptome. • Stress-driven promoters realized feedback control of tolerance genes. • Yeast robustness was improved by intensifying antioxidant system. • Ethanol titer of the engineered strain increased by 49.5% at high temperature. [ABSTRACT FROM AUTHOR]

The high substrate variability and complexity of fermentation media derived from lignocellulosic feedstock affects the concentration profiles and the length of the fermentation. Failing to account for such variability raises operational and scheduling issues and affects the overall performance of these processes. In this work, a hybrid soft sensor was developed to monitor and forecast the evolution of cellulose‐to‐ethanol fermentation. The soft sensor consisted of two modules (a data‐driven model and a kinetic model) connected sequentially. The data‐driven module used a partial‐least‐squares model to estimate the current state of glucose from spectroscopic data. The kinetic model was recursively fitted to known concentrations of glucose to update the long‐horizon predictions of glucose, xylose, and ethanol. This combination of real‐time data update from an actual fermentation process to a high‐fidelity kinetic model constitutes the basis of the digital twin concept and allows for a better real‐time understanding of complex inhibition phenomena caused by different inhibitors commonly found in lignocellulosic feedstocks. The soft sensor was experimentally validated with three different cellulose‐to‐ethanol fermentations and the results suggested that this method is suitable for monitoring and forecasting fermentation when the measurements provide reasonably good estimates of the real state of the system. These results would allow the flexibility of the operation of cellulosic processes to be increased, and would permit the scheduling to be adapted to the inherent variability of such substrates © 2020 Society of Chemical Industry and John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Background: Consolidated bioprocessing, which combines saccharolytic and fermentative abilities in a single microorganism, is receiving increased attention to decrease environmental and economic costs in lignocellulosic biorefineries. Nevertheless, the economic viability of lignocellulosic ethanol is also dependent of an efficient utilization of the hemicellulosic fraction, which contains xylose as a major component in concentrations that can reach up to 40% of the total biomass in hardwoods and agricultural residues. This major bottleneck is mainly due to the necessity of chemical/enzymatic treatments to hydrolyze hemicellulose into fermentable sugars and to the fact that xylose is not readily consumed by Saccharomyces cerevisiae—the most used organism for large-scale ethanol production. In this work, industrial S. cerevisiae strains, presenting robust traits such as thermotolerance and improved resistance to inhibitors, were evaluated as hosts for the cell-surface display of hemicellulolytic enzymes and optimized xylose assimilation, aiming at the development of whole-cell biocatalysts for consolidated bioprocessing of corn cob-derived hemicellulose. Results: These modifications allowed the direct production of ethanol from non-detoxified hemicellulosic liquor obtained by hydrothermal pretreatment of corn cob, reaching an ethanol titer of 11.1 g/L corresponding to a yield of 0.328 g/g of potential xylose and glucose, without the need for external hydrolytic catalysts. Also, consolidated bioprocessing of pretreated corn cob was found to be more efficient for hemicellulosic ethanol production than simultaneous saccharification and fermentation with addition of commercial hemicellulases. Conclusions: These results show the potential of industrial S. cerevisiae strains for the design of whole-cell biocatalysts and paves the way for the development of more efficient consolidated bioprocesses for lignocellulosic biomass valorization, further decreasing environmental and economic costs. [ABSTRACT FROM AUTHOR]

Agricultural practices generate lignocellulosic waste that can be bioconverted by fungi to generate value-added products such as biofuels. In this context, fungal enzymes are presented as an alternative for their use in the hydrolysis of cellulose to sugars that can be fermented to ethanol. The aim of this work was to characterize LBM 033 strain and to analyze its efficiency in the hydrolysis of cellulosic substrates, including barley straw. LBM 033 strain was identified as Trametes villosa by molecular techniques, through the use of the ITS and rbp2 markers and the construction of phylogenetic trees. The cell-free supernatant of T. villosa LBM 033 showed high titers of hydrolytic enzymatic activities, necessary for the hydrolysis of the holocellulosic substrates, hydrolyzing pure cellulose to cellobiose and glucose and also degraded the polysaccharides contained in barley straw to short soluble oligosaccharides. These results indicate that macro fungi from tropical soil environments, such as T. villosa LBM 033 can be a valuable resource for in-house, cost effective production of enzymes that can be applied in the hydrolysis stage, which could reduce the total cost of bioethanol production. [ABSTRACT FROM AUTHOR]

Objectives: Major lignocellulosic inhibitory compounds found in sugarcane-based industrial hydrolysate samples were tested in laboratory and industrial yeast strains, as well as in lactic acid bacteria, in order to verify their effects on important physiological parameters. Results: Saccharomyces cereviaise SA-1, an industrial strain, stood out as compared to the remaining strains for virtually all inhibitors investigated. This strain presented the highest growth rate and the lowest lag-phase in the presence of acetic acid, levulinic acid, p-coumaric acid, ferulic acid, and HMF, when compared to the other strains. In sugarcane-based hydrolysate fermentations, both SA-1 and CEN.PK113-7D presented similar fermentation performances. Industrial isolates of contaminating lactic acid bacteria were evaluated in the presence of an inhibitory cocktail, containing a mixture of 76.6 mM acetic acid, 1.3 mM HMF, 7.1 mM furfural, and 1.9 mM p-coumaric acid. Whilst all yeast strains were unable to grow under such conditions, bacteria had an average inhibition of roughly 50% on their growth rates. Conclusions: Overall, industrial strain SA-1 might be a promising microbial chassis for second generation ethanol production and for future metabolic and evolutionary engineering strategies, and for strain robustness understanding. [ABSTRACT FROM AUTHOR]

Yeast-based bioethanol production from lignocellulosic hydrolysates (LH) is an attractive and sustainable alternative for biofuel production. However, the presence of acetic acid (AA) in LH is still a major problem. Indeed, above certain concentrations, AA inhibits yeast fermentation and triggers a regulated cell death (RCD) process mediated by the mitochondria and vacuole. Understanding the mechanisms involved in AA-induced RCD (AA-RCD) may thus help select robust fermentative yeast strains, providing novel insights to improve lignocellulosic ethanol (LE) production. Herein, we hypothesized that zinc vacuolar transporters are involved in vacuole-mediated AA-RCD, since zinc enhances ethanol production and zinc-dependent catalase and superoxide dismutase protect from AA-RCD. In this work, zinc limitation sensitized wild-type cells to AA-RCD, while zinc supplementation resulted in a small protective effect. Cells lacking the vacuolar zinc transporter Zrt3 were highly resistant to AA-RCD, exhibiting reduced vacuolar dysfunction. Moreover, zrt3Δ cells displayed higher ethanol productivity than their wild-type counterparts, both when cultivated in rich medium with AA (0.29 g L−1 h−1 versus 0.11 g L−1 h−1) and in an LH (0.73 g L−1 h−1 versus 0.55 g L−1 h−1). Overall, the deletion of ZRT3 emerges as a promising strategy to increase strain robustness in LE industrial production.

In the lignocellulosic yeast development, metabolic burden relates to redirection of resources from regular cellular activities toward the needs created by recombinant protein production. As a result, growth parameters may be greatly affected. Noteworthy, Saccharomyces cerevisiae M2n[pBKD2-Pccbgl1]-C1, previously developed by multiple δ-integration of the β-glucosidase BGL3, did not show any detectable metabolic burden. This work aims to test the hypothesis that the metabolic burden and the metabolomic perturbation induced by the δ-integration of a yeast strain, could differ significantly. The engineered strain was evaluated in terms of metabolic performances and metabolomic alterations in different conditions typical of the bioethanol industry. Results indicate that the multiple δ-integration did not affect the ability of the engineered strain to grow on different carbon sources and to tolerate increasing concentrations of ethanol and inhibitory compounds. Conversely, metabolomic profiles were significantly altered both under growing and stressing conditions, indicating a large extent of metabolic reshuffling involved in the maintenance of the metabolic homeostasis. Considering that four copies of BGL3 gene have been integrated without affecting any parental genes or promoter sequences, deeper studies are needed to unveil the mechanisms implied in these metabolomic changes, thus supporting the optimization of protein production in engineered strains.

• Whole sorghum biomass was treated using steam-explosion at various severities. • Single-step recovery of extractives and hemicelluloses was achieved. • 3 min retention time at 180 °C recovered 30 wt% of monomeric carbohydrates (dw). • No additional depolymerization steps were required at selected treatment conditions. • Saccharomyces cerevisiae fermentation assays led to above 95% ethanol yields. Maximizing the extracted carbohydrates from lignocellulosic biomass represents one critical step towards a wide implementation of industrial-scale second-generation ethanol production. To this purpose, a novel steam-based treatment strategy targeting the whole sweet sorghum biomass was developed. This extraction was followed by a non-enzymatic hydrolysis of the hemicellulose fraction and ethanol fermentation. By doing so, both the free carbohydrates present in the plant stems as well as the hemicelluloses trapped inside the various structural components were recovered and converted. A statistical design of experiments (DoE) approach was developed to investigate the most suitable steam-treatment severity to maximize the recovery of these carbohydrates while simultaneously minimizing the production of fermentation inhibitors. The severity of the treatment was estimated from the combined effects of temperature (150 °C – 210 °C) and cooking time (1–7 min). The optimal treatment conditions identified in this work (3 min retention time at 180 °C) successfully allowed recovering 30% of monomeric carbohydrates (based on sorghum dry weight). Three of the most efficient steam-explosion severities were investigated further in order to evaluate their impact on the subsequent ethanol fermentation using Saccharomyces cerevisiae yeast. A maximum ethanol yield of above 95% was achieved using the mixed carbohydrate streams recovered using the optimal steam-based extraction conditions. Thus, the present work thoroughly describes for the first time and to the best of our knowledge, a single-stage recovery of sorghum extractives and hemicelluloses, followed by their efficient fermentation to ethanol. [ABSTRACT FROM AUTHOR]

Lowering the price of enzymes is one of the key challenges to stablish the full potential of lignocellulosic biorefineries. Lignocellulolytic enzymes are used to deconstruct the complex plant cell wall, releasing fermentable sugars that can be further used in the production of lignocellulosic ethanol. Countries like Brazil, India, and China are already blending or considering blending ethanol in different proportions to gasoline, to be used in combustion engines. Fungal co-cultures are an alternative way of producing lignocellulolytic enzymes. In this review, we discuss the use of fungal co-cultures as an alternative for the on-site production of lignocellulolytic enzymes. The basic concepts and applications of fungal co-cultures are presented, covering most used strains, systems, advances achieved and challenges ahead. Co-cultures are an alternative technique to produce carbohydrate-active enzymes, and several studies highlighted here demonstrate their potential to contribute to the expansion of lignocellulosic biorefineries. However, there are still several aspects of fungal co-cultures that are not understood and need to be addressed to enable fungal co-cultures for commercial enzyme production. The necessity for more detailed studies, especially regarding the molecular interactions between participant fungi, are stressed in the article. • Reutilization of biomass is one of the key strategies to implement a new bio-based economy. • Fungal co-cultures are a promising strategy to implement cell wall-degrading enzyme production for biorefinery use. • Co-cultures of filamentous fungi can increase certain enzyme activities, however other activities may be diminished. • New Omics studies are fundamental to improve molecular understating of fungal interactions. [ABSTRACT FROM AUTHOR]

Abstract Lignin-rich digested stillage as a novel feedstock for biochar production was subjected to slow pyrolysis. The lignin residue stemmed from a lignocellulosic ethanol pilot run with poplar, from which the stillage was anaerobically digested prior to pyrolysis. Pyrolysis conditions were optimized to meet guidelines put forth by the International Biochar Initiative and the European Biochar Certificate (molar H/C org ratio < 0.7 and O/C org ratio < 0.4), as biochar could be carbon-negative upon soil amendment, while reallocating nutrients to the field. Bench-scale pyrolysis of the lignin residue and straw were conducted according to a 33 factorial design with center runs (ranges: 370–450 °C highest treatment temperature, 5–45 min holding time and 5–50 °C.min−1 heating rate). Parametric and nonparametric statistics revealed that the highest treatment temperature was by far the most influencing factor for both feedstocks which 'pushed' H/C and O/C ratios within the desired range. Lignin-based biochar can be obtained with 50.7% yield, a H/C ratio of 0.70 and an O/C ratio of 0.20, already at 384 °C. This is considerably better when compared to straw-based biochar with identical H/C and O/C ratios, which came with a lower yield (33.7%) and required a modestly higher temperature (410 °C). Results from this study emphasize the feasibility to integrate slow pyrolysis in a lignocellulosic biorefinery. Graphical abstract Image 1 Highlights • Lignin residue from digested stillage was pyrolysed to biochar for the first time. • Temperature, heating rate and holding time were varied in a 33 factorial design. • Statistical models were used for process optimization to meet biochar standards. • The quality-quantity trade-off during pyrolysis was assessed. • At 384 °C, lignin-biochar with H/C = 0.7 and O/C = 0.2 is obtained with 50.71% yield. [ABSTRACT FROM AUTHOR]

Abstract Sorghum bicolor (L.) (Moench), which stands out for dry matter yield per hectare, has been considered as potential raw material for biofuels and electricity generation. It has a production cycle of six months, possibility of mechanization of cultivation and harvest and good adaptation to most regions of Brazil. Sorghum genotypes were evaluated for agronomic potential and chemical composition favorable to the production of second-generation ethanol. Three brown midrib (bmr) sorghum mutant hybrids were compared to three conventional hybrids. The bmr sorghum mutant hybrids are associated with reduced lignin content, making these genotypes more promising to the enzymatic conversion processes of the biomass. Sorghum biomass showed a high potential in terms of biomass production, with an average dry matter yield of 26.57 Mg ha−1. Brown midrib sorghum hybrids showed significantly lower lignin contents than conventional hybrids and demonstrated the potential for cellulosic ethanol production. Highlights • Sorghum biomass presented high biomass production potential. • The genotypes as brown midrib sorghum mutant hybrids differ in amount of lignin in relation to the conventional genotypes. • There was no interaction between genotypes and environments. [ABSTRACT FROM AUTHOR]

Advanced generation biofuel production from lignocellulosic material (LCM) was investigated. A range of different thermo-chemical pre-treatments were evaluated with different LCM. The pre-treatments included; alkaline (5% NaOH at 50°C), acid (1% H2SO4 at 121°C) and autohydrolytical methods (200°C aqueous based hydrothermal) and were evaluated using samples of miscanthus, wheat-straw and willow. The liberation of sugars, presence of inhibitory compounds, and the degree of enhancement of enzymatic saccharification was accessed. The suitability of the pre-treatment generated hydrolysates (as bioethanol feedstocks for Saccharomyces cerevisiae) was also accessed using a phenotypic microarray that measured yeast metabolic output. The use of the alkaline pre-treatment liberated more glucose and arabinose into both the pre-treatment generated hydrolysate and also the hydrolysate produced after enzymatic hydrolysis (when compared with other pre-treatments). However, hydrolysates derived from use of alkaline pre-treatments were shown to be unsuitable as a fermentation medium due to issues with colloidal stability (high viscosity). Use of acid or autohydrolytical pre-treatments liberated high concentrations of monosaccharides regardless of the LCM used and the hydrolysates had good fermentation performance with measurable yeast metabolic output. Acid pre-treated wheat straw hydrolysates were then used as a model system for larger scale fermentations to confirm both the results of the phenotypic microarray and its validity as an effective high-throughput screening tool.

Integrated permeate channel (IPC) flat sheet membranes were examined for use as a reverse membrane bioreactor (rMBR) for lignocellulosic ethanol production. The fermenting organism, Saccharomyces cerevisiae (T0936), a genetically-modified strain with the ability to ferment xylose, was used inside the rMBR. The rMBR was evaluated for simultaneous glucose and xylose utilization as well as in situ detoxification of furfural and hydroxylmethyl furfural (HMF). The synthetic medium was investigated, after which the pretreated wheat straw was used as a xylose-rich lignocellulosic substrate. The IPC membrane panels were successfully used as the rMBR during the batch fermentations, which lasted for up to eight days without fouling. With the rMBR, complete glucose and xylose utilization, resulting in 86% of the theoretical ethanol yield, was observed with the synthetic medium. Its application with the pretreated wheat straw resulted in complete glucose consumption and 87% xylose utilization; a final ethanol concentration of 30.3 g/L was obtained, which corresponds to 83% of the theoretical yield. Moreover, complete in situ detoxification of furfural and HMF was obtained within 36 h and 60 h, respectively, with the rMBR. The use of the rMBR is a promising technology for large-scale lignocellulosic ethanol production, since it facilitates the co-utilization of glucose and xylose; moreover, the technology would also allow the reuse of the yeast for several batches.

Switchgrass is native to the tallgrass prairie of North America. It is self-incompatible and has varied ploidy levels from diploid (2x) to dodecaploid (12x) with tetraploid and octoploid being the most common. The high yielding potential and the ability to grow well in marginal lands make switchgrass an ideal species as a dedicated biomass producer for lignocellulosic ethanol production. Genetic transformation is an important tool for studying gene function and for germplasm improvement in switchgrass, the genome of which has been sequenced recently. This paper intends to provide a comprehensive review on plant regeneration and genetic transformation in switchgrass. We first reviewed the effect of explants, basal medium and plant growth regulators on plant regeneration in switchgrass, which is a prerequisite for genetic transformation. We then reviewed the progresses on genetic transformation with either the biolistic or Agrobacterium-mediated method in switchgrass, and discussed various techniques employed to improve the transformation efficiency. Finally we reviewed the recent progresses on the use of genetic transformation in improving biomass quality such as the reduction of lignin, and in increasing biomass yield in switchgrass. We also provided a future perspective on the use of new genome editing technologies in switchgrass and its potential impact on regulatory processes.

Lignocellulosic ethanol represents a renewable alternative to petrol. Miscanthus, a perennial plant that grows on marginal land, is characterized by efficient use of resources and is considered a promising source of lignocellulosic biomass. A life cycle assessment (LCA) was performed to determine the environmental impacts of ethanol production from miscanthus grown on marginal land in Great Britain (Aberystwyth) and an average‐yield site in Germany (Stuttgart; functional unit: 1 GJ). As the conversion process has substantial influence on the overall environmental performance, the comparison examined three pretreatment options for miscanthus. Overall, results indicate lower impacts for the production in Stuttgart in comparison with the corresponding pathways in Aberystwyth across the analysed categories. Disparities between the sites were mainly attributed to differences in biomass yield. When comparing the conversion options, liquid hot water treatment resulted in the lowest impacts, followed by dilute sulphuric acid. Dilute sodium hydroxide pretreatment represented the least favourable option. Site‐dependent variation in biomass composition and degradability did not have substantial influence on the environmental performance of the analysed pathways. Additionally, implications of replacing petrol with miscanthus ethanol were examined. Ethanol derived from miscanthus resulted in lower impacts with respect to greenhouse gas emissions, fossil resource depletion, natural land transformation and ozone depletion. However, for other categories, including toxicity, eutrophication and agricultural land occupation, net scores were substantially higher than for the fossil reference. Nevertheless, the results indicate that miscanthus ethanol produced via dilute acid and liquid hot water treatment at the site in Stuttgart has the potential to comply with the requirements of the European Renewable energy directive for greenhouse gas emission reduction. For ethanol production at the marginal site, carbon sequestration needs to be considered in order to meet the requirements for greenhouse gas mitigation. Lignocellulosic ethanol represents a renewable alternative to petrol. Miscanthus, a perennial plant, is characterised by efficient resource use and is considered a promising source of lignocellulosic biomass. A LCA was performed to compare the environmental impacts of ethanol production from miscanthus grown on marginal land and an average‐yield site. In addition, three pretreatment options for miscanthus were compared. Results indicate lower impacts for the production at the average site, with the disparities mainly attributable to differences in biomass yield. Irrespective of the site, liquid hot water treatment has shown to be the pretreatment option with the lowest impacts overall. [ABSTRACT FROM AUTHOR]

The effects of pretreatments applied to raw materials and microorganism selection in lignocellulosic bioethanol production were investigated. It has been found that the yield of enzymatic pretreatment process applied after the chemical pretreatment is about 4 times higher than that only chemical. Enzymatic pretreatment used process yield is 3.5 times higher than that chemical pretreatment. When the microorganism ethanol production yield values of Saccharomyces cerevisiae and Pichia stipitis were examined, it was found that S.cerevisiae was superior to P.stipitis in chemical pretreated reactors (about 1.7 times higher) while P. stipitis' yield was higher about 1.2 times in enzymatic pretreated reactors. When the reactors which have been pretreated with both chemical and enzymatic hydrolysis and P. stipitis and S. cerevisiae used separately were examined, it was observed that there was not a great difference in terms of ethanol production yield. C. thermocellum's ethanol yield was found about 3 times lower than the S. cerevisiae and P. stipitis. According to the obtained data, it was seen that S. cerevisiae could produce ethanol with higher efficiency than P. stipitis. At the same time, the difficulty of C. thermocellum's production conditions, high energy demand and high risk of contamination, and low ethanol production yield, it is thought that it can only be used in the research phase for now. But in particular, by investigating extracellular cellulase enzyme system of C. thermocellum, genetic modifications are predicted to play an important role in the future in the second generation bioethanol production process. [ABSTRACT FROM AUTHOR]

The economics of Recycled Paper Sludge conversion into ethanol was here assessed with emphasis on integrating a cellulase recycling system. Without cellulases recycling this process presented positive economic outputs (payback period of 7.85 years; 10.90 Million US$ of accumulated NPV) despite the modest ethanol titers. Recycling both free and solid-bound enzymes allowed considerable savings of enzyme but also an increase on annual costs (0.88%), resulting on a superior economic output: payback period decreased to 7.25 years; accumulated NPV increased to 14.44 Million US$. Recycling exclusively the liquid fraction enabled a clear costs reduction, however, also total ethanol decreased, attenuating the abovementioned benefits. Targeting higher ethanol concentrations, superior solids consistencies were also evaluated. Despite a costs reduction, total ethanol decreased due to a higher ethanol retention on the solid. A sensitivity analysis further revealed that the cost of enzymes and ultrafiltration membrane may be critical on enzyme recycling economic feasibility. [ABSTRACT FROM AUTHOR]

Abstract Chain elongation is a promising mixed culture bioprocess to convert acetate into medium chain carboxylates with ethanol as an electron donor. Caproate production using lignocellulosic ethanol (LE) as feedstock via chain elongation fermentation was examined in this study. Meanwhile, the effects of yeast extract and cellulose containing in the LE were investigated separately. Fermentation performance showed that the lag phase of caproate production were shortened in experimental group LE (4 days), yeast extract (6 days), and cellulose (9 days) compared with the control group (17 days) without extra supplement. The insufficiency of electron donor, ethanol, limited further elongation into caproate, resulting in comparable caproate yields and carbon conversion ratios in four experimental groups. Microbial community and microbial kinetics analysis revealed that yeast extract could be metabolized by protein-utilizing bacteria into short chain carboxylates (SCCs), which facilitated biological chain elongation. Meanwhile, yeast extract boosted microbial growth by serving as nitrogen and other nutrient sources. Furthermore, cellulose was utilized and further converted into SCCs, or even caproate, by cellulolytic bacteria. Together, caproate production was enhanced with high microbial activities and intermediates formation using LE. This study upgrades LE into a higher energy density product, caproate, via the energy-efficient chain elongation fermentation. Graphical abstract Image 1 Highlights • Lag phase of caproate formation was shortened by 13 d with lignocellulosic ethanol. • Insufficiency of ethanol limited further elongation of butyrate into caproate. • Lignocellulosic ethanol as feedstock enriched the microbial community. • Cellulose and yeast extract shortened the lag phase of caproate production. • Yeast extract boosted bacterial growth thus improving fermentation performance. [ABSTRACT FROM AUTHOR]

Sweet sorghum was subjected to an impregnation step, which recovered most of the 1st generation sugars, prior to a steam-treatment extraction of the 2nd generation sugars, at three different severity factors (SF). A medium severity (3.56 SF) treatment proved to be an optimal compromise between the amount of sugars extracted and the fermentation inhibitors generated following the subsequent depolymerization approaches applied on the broth. Next, a series of detoxification approaches (ozonation, overliming and a combination of both) were investigated following a concentration and depolymerization step. Results show that higher steam-treatment severity required more intense detoxification steps. However, when combining the 1st and 2nd generation streams at a 2:1 ratio, the inhibitors did not affect the fermentation process and ethanol yields above 90% of the theoretical maximum were achieved. [ABSTRACT FROM AUTHOR]

Energy security, environmental concerns, and unstable oil prices have been the driving trifecta of demand for alternative fuels in the United States. The United States’ dependence on energy resources, often from unstable oil-producing countries has created political insecurities and concerns. As we try to gain energy security, unconventional oil becomes more common, flooding the market, and causing the major downshift of the usual unstable oil prices. Meanwhile, consumption of fossil fuels and the consequent CO 2 emissions have driven disruptions in the Earth’s atmosphere and are recognized to be responsible for global climate change. While the significance of each of these three factors may fluctuate with global politics or new technologies, transportation energy will remain the prominent focus of multi-disciplined research. Bioenergy future depends on the price of oil. Current energy policy of the United States heavily favors petroleum industry. In this review, the current trend in microbial lipids as a potential biofuel is discussed. [ABSTRACT FROM AUTHOR]

We investigated the yeast species associated with rotting wood samples obtained from Brazilian ecosystems, with a special focus on cellobiose-fermenting species. About 647 yeast strains were isolated from rotting wood samples collected from the areas of Atlantic rainforest, Cerrado, and Amazonian forest. Eighty-six known species and 47 novel species of yeasts were isolated. Candida boidinii, Cyberlindnera subsufficiens, Meyerozyma guilliermondii, Schwanniomyces polymorphus, Candida natalensis , and Debaryomyces hansenii were the most frequently isolated species. Among the cellobiose-fermenting yeasts, 14 known and three novel yeast species were identified. Scheffersomyces queiroziae, Sc. amazonensis, Yamadazyma sp.1, Hanseniaspora opuntiae , C. jaroonii , and Candida tammaniensi s were the main ethanol-producing yeasts. These species also produced an intracellular β-glucosidase responsible for cellobiose hydrolysis. In fermentation assays using a culture medium containing 50 g L −1 cellobiose, ethanol production was observed in all cases; Sc. queiroziae and Sc. amazonensis showed the highest yield, efficiency, and productivity. Candida jaroonii and Yamadazyma sp.1 strains also showed high efficiency in cellobiose fermentation, while C. tammaniensis and H. opuntiae strains produced low amounts of ethanol. This study shows the potential of rotting wood samples from Brazilian ecosystems as a source of yeasts, including new species as well as those with promising biotechnological properties. [ABSTRACT FROM AUTHOR]

Abstract: The bioconversion of lignocellulosic biomasses to ethanol consists of three main steps: pre‐treatment, enzymatic hydrolysis, and fermentation by microorganisms. Most pre‐treatments induce the formation of substances with a potential inhibitory effect on the microbial metabolism, which may hinder the process. The objective of this study was to investigate the behaviour of Saccharomyces cerevisiae PE‐2 yeast in the presence of four phenolic compounds (vanillin, syringaldehyde, syringic acid, and acetosyringone) resulting from the alkaline pre‐treatment of eucalyptus with green liquor. Eucalyptus is a fast‐growing tree, widely exploited by the paper and pulp industry in Brazil. It was observed that yeast growth and glucose assimilation were affected to an extent directly proportional to the initial amount of vanillin in the medium. Syringaldehyde in a concentration of 1.0 g/L had an adverse effect on the fermentation parameters related to ethanol production, which exhibited a decrease of approximately 50 %. When syringic acid and acetosyringone were used, although the cell growth and glucose consumption profiles were similar to those of the control, they inhibited the conversion at concentrations of 0.1 and 1.0 g/L. [ABSTRACT FROM AUTHOR]

Copyright of Agriscientia is the property of Revista AgriScientia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)