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Despite the significant progress in the research, the problem of finding an efficient method for producing bioethanol from renewable lignocellulosic waste materials remains unresolved. Our investigation aimed to assess the efficacy of ethanol production from sugar beet pulp (SBP) utilising various approaches, including pretreatment variations, enzymatic processes, and microbial hydrolysis. Our research involved using the post-cultivation concentrate of T. viride LOCK 0588 grown in the SBP-based medium as a source of enzymes. The SBP hydrolysis process was carried out for 48 h at 50 °C. The quantity of sugar released, up to 61 g dm−3, through the utilisation of this extract proved to be on par with the outcomes achieved by the application of the commercial Cellic Ctec2 preparation. The final yields of the ethanol production with the use of the coculture of S. cerevisiae (Ethanol Red) and Scheffersomyces stipitis LOCK 0047 strain were in the range 5.1 ± 0.11 kg 100 kg−1 ÷ 5.38 ± 0.11 kg 100 kg−1. These results provide a solid basis for improving larger-scale industrial procedures that involve converting SBP into bioethanol using a cost-efficient approach of microbial hydrolysis with T. viride and a blend of pentose and hexose fermenting yeast. [ABSTRACT FROM AUTHOR]

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Agricultural residues (e.g. corn stover (CS)) representing a huge lignocellulosic biomass waste are regarded as a promising renewable resource that can be converted to fuels and chemicals via biochemical route. Nevertheless, the unfavorable properties, such as low bulk density, contamination by microorganisms, fluffy and thereby difficult to handle, cause huge problems for biomass logistics and biomass conversion. Furthermore, traditional biomass pretreatment methods often use severe conditions, consume much energy, difficult to scale up and generate a feedstock with many toxic degradation products that inhibit fermentation. In this study, we developed a novel, low-cost and easy-to-implement pretreatment method: "Densifying Lignocellulosic biomass with acidic Chemicals (DLC)" on CS. The DLC-CS owning a uniform shape showed a bulk density 4 times higher compared to loose CS and was highly resistant to microbial contamination, which greatly facilitates biomass handling, transportation and storage. DLC-CS after regular steam autoclave treatment at 121 ○C exhibited high enzymatic digestibility and much higher fermentability compared to traditional dilute acid pretreatment. An ethanol titer as high as 68.1 g/L was achieved without washing or detoxification of the pretreated biomass. The superior performances of DLC for biomass logistics and biomass conversion render it very promising for industrial use. • A novel lignocellulosic biomass pretreatment method was developed. • This method increased biomass bulk density and prevented microbial contamination. • The pretreated biomass showed high digestibility and high fermentability. • A high ethanol titer (68.1 g/L) was achieved without washing or detoxification. • This method facilitates biomass logistics and greatly reduces pretreatment costs. [ABSTRACT FROM AUTHOR]

Background: As one of the clean and sustainable energies, lignocellulosic ethanol has achieved much attention around the world. The production of lignocellulosic ethanol does not compete with people for food, while the consumption of ethanol could contribute to the carbon dioxide emission reduction. However, the simultaneous transformation of glucose and xylose to ethanol is one of the key technologies for attaining cost-efficient lignocellulosic ethanol production at an industrial scale. Genetic modification of strains and constructing consortia were two approaches to resolve this issue. Compared with strain improvement, the synergistic interaction of consortia in metabolic pathways should be more useful than using each one separately. Results: In this study, the consortia consisting of suspended Scheffersomyces stipitis CICC1960 and Zymomonas mobilis 8b were cultivated to successfully depress carbon catabolite repression (CCR) in artificially simulated 80G40XRM. With this strategy, a 5.52% more xylose consumption and a 6.52% higher ethanol titer were achieved by the consortium, in which the inoculation ratio between S. stipitis and Z. mobilis was 1:3, compared with the Z. mobilis 8b mono-fermentation. Subsequently, one copy of the xylose metabolic genes was inserted into the Z. mobilis 8b genome to construct Z. mobilis FR2, leading to the xylose final-consumption amount and ethanol titer improvement by 15.36% and 6.81%, respectively. Finally, various corn stover hydrolysates with different sugar concentrations (glucose and xylose 60, 90, 120 g/L), were used to evaluate the fermentation performance of the consortium consisting of S. stipitis CICC1960 and Z. mobilis FR2. Fermentation results showed that a 1.56–4.59% higher ethanol titer was achieved by the consortium compared with the Z. mobilis FR2 mono-fermentation, and a 46.12–102.14% higher ethanol titer was observed in the consortium fermentation when compared with the S. stipitis CICC1960 mono-fermentation. Furthermore, qRT-PCR analysis of xylose/glucose transporter and other genes responsible for CCR explained the reason why the initial ratio inoculation of 1:3 in artificially simulated 80G40XRM had the best fermentation performance in the consortium. Conclusions: The fermentation strategy used in this study, i.e., using a genetically modified consortium, had a superior performance in ethanol production, as compared with the S. stipitis CICC1960 mono-fermentation and the Z. mobilis FR2 mono-fermentation alone. This result showed that this strategy has potential for future lignocellulosic ethanol production. [ABSTRACT FROM AUTHOR]

Paper mulberry, a fast-growing and vigorous plant, is a potential substrate for producing lignocellulosic bioethanol and an important renewable alternative to fossil fuels. In order to improve the economic feasibility of ethanol production from paper mulberry, H 3 PO 4 /H 2 O 2 pretreatment was selected as the most suitable pretreatment method that could produce the highest glucose concentration (131 g/L) compared with other pretreatments (73.2–89.3 g/L) at high solid loading. Whereafter, the final solid loading of H 3 PO 4 /H 2 O 2 pretreatment was significantly increased to 40% (w/v) without any decrease in the final glucose concentration. Finally, a novel Fed-nonisothermal-simultaneous saccharification and fermentation was constructed using H 3 PO 4 /H 2 O 2 pretreated paper mulberry, which bypassed the inhibition caused by paper mulberry solid and high temperature on the traditional simultaneous saccharification and fermentation, improving ethanol concentration (63.9 g/L), ethanol productivity (1.33 g/L/h) and ethanol yield (0.160 g/g-biomass) by 30.4%, 30.4% and 30.1%, respectively, compared to those obtained from SSF (simultaneous saccharification and fermentation) process. Thus, we have opened up a novel way to produce ethanol or other biofuels using the paper mulberry as an outstanding alternative substrate. • We are the first to produce ethanol from paper mulberry. • An extremely high solid loading (40%) was used in the pretreatment process. • A novel Fed-nonisothermal-SSF was developed, improving ethanol yield by 30.1%. [ABSTRACT FROM AUTHOR]

Summary: In this study, various functions were evaluated and utilized to forecast observed values and kinetic parameters of the batch ethanol fabrication from carob extract in the suspended‐cell stirred tank reactor (SCSTR). The best model was detected with the model comparison parameters (root‐mean‐square‐error [RMSE], mean‐absolute‐error [MAE], and R2). The results indicated that the model Stannard (ST) successfully predicted biomass production data (RMSE = 0.26 g L−1, MAE = 0.18 g L−1, and R2 = 0.9910), ethanol fabrication data (RMSE = 2.44 g L−1, MAE = 1.88 g L−1, and R2 = 0.9809), and sugar depletion data (RMSE = 2.82 g L−1, MAE = 2.17 g L−1 and R2 = 0.9938). Nevertheless, the lowest value of the objective function (Φ‐factor) was also yielded as 0.041 using the model ST. Additionally, in the estimation of the kinetic data, the model ST also gave well‐directed results. Besides, when an independent set of the observed values was utilized to confirm the mathematical functions, the satisfactory consequences were achieved in terms of both the experimental and kinetic values. Consequently, the model ST can work as a universal function in predicting observed values and kinetics of batch ethanol generation from carob extract in an SCSTR. [ABSTRACT FROM AUTHOR]

• Acetic acid pretreatment was proposed as a fractionation method. • R 0 10 was selected due of the compromise of delignification/yield/digestibility. • The reuse of black liquor apparently did not affect the bioconversion of CAB. • The ethanol production reached up to 17.11 g/L using 10% pretreated CAB. • SPF values increased 88.3% after addition of 5% lignin in sunscreen lotion. The present study focuses on the fractionation of cashew apple bagasse via a pretreatment using acetic acid as a delignifying agent and sulfuric acid as an external catalyst. As expected, the concentrations of both acids and the incubation time dramatically affected delignification and hemicellulose solubilization. Under the optimal pretreatment conditions, recycling of the spent liquor had no apparent impact on the chemical composition of the pretreated material, yield of sugar produced via enzymatic hydrolysis (∼37 g/L reducing sugars at 7.5% (w/v) solid loading), or yield of ethanol obtained via fermentation with Saccharomyces cerevisiae (∼16 g/L at 10% (w/v) solid loading). The lignin recovered from the spent liquor showed a good ultraviolet protective effect; the addition of 5% (w/w) of the biopolymer increased the sun protection factor of a commercial sunscreen lotion from 21.62 to 40.71. The combined use of hydrogen peroxide and ultraviolet radiation reduced the organosolv lignin color (absorbance at 450 nm was four times lower) owing to aromatic ring cleavage, but cosmetics containing whitened organosolv lignin had low sun protection factor values. In summary, the results obtained in this study demonstrate the utility of organic acid pretreatment in the valorization of lignocellulosic materials. [ABSTRACT FROM AUTHOR]

In this study chemical and enzymatic treatment of hemp biomass were optimized to obtain maximum ethanol production. In the first stage, physical and chemical pretreatment of hemp biomass was carried out. It was found that the Tygra variety is susceptible to alkaline treatment at an optimum concentration of 2% NaOH. Next, the effect of NaOH on the value of reducing sugars and the chemical composition of the solid fraction before and after the treatment was determined. Hemp biomass before and after the chemical treatment was analysed by FTIR spectra and SEM. The effect of enzymatic hydrolysis, i.e., substrate content, temperature, time, pH and dose of enzyme by means of Response Surface Methodology on glucose content was determined. The highest glucose value was observed at 50 °C, in time process between 48 and 72 h, and the dose of enzyme was not less than 20 FPU·g−1. After the optimization of enzymatic hydrolysis two processes of ethanol fermentation from hemp biomass, SHF and SSF, were carried out. In the SHF process a 40% higher concentration of ethanol was obtained (10.51 g/L). In conclusion, hemp biomass was found to be an interesting and promising source to be used for bioethanol production. [ABSTRACT FROM AUTHOR]

Abstract Background Bioethanol from lignocellulosic materials is of great significance to the production of renewable fuels due to its wide sources. However, multiple inhibitors generated from pretreatments represent great challenges for its industrial-scale fermentation. Despite the complex toxicity mechanisms, lignocellulose-derived inhibitors have been reported to be related to the levels of intracellular reactive oxygen species (ROS), which makes oxidoreductase a potential target for the enhancement of the tolerance of yeasts to these inhibitors. Results A typical 2-Cys peroxiredoxin from Kluyveromyces marxianus Y179 (KmTPX1) was identified, and its overexpression was achieved in Saccharomyces cerevisiae 280. Strain TPX1 with overexpressed KmTPX1 gene showed an enhanced tolerance to oxidative stresses. Serial dilution assay indicated that KmTPX1 gene contributed to a better cellular growth behavior, when the cells were exposed to multiple lignocellulose-derived inhibitors, such as formic acid, acetic acid, furfural, ethanol, and salt. In particular, KmTPX1 expression also possessed enhanced tolerance to a mixture of formic acid, acetic acid, and furfural (FAF) with a shorter lag period. The maximum glucose consumption rate and ethanol generation rate in KmTPX1-expressing strain were significantly improved, compared with the control. The mechanism of improved tolerance to FAF depends on the lower level of intracellular ROS for cell survival under stress. Conclusion A new functional gene KmTPX1 from K. marxianus is firstly associated with the enhanced tolerance to multiple lignocellulose-derived inhibitors in S. cerevisiae. We provided a possible detoxification mechanism of the KmTPX1 for further theoretical research; meanwhile, we provided a powerful potential for application of the KmTPX1 overexpressing strain in ethanol production from lignocellulosic materials.

Cassava starch is an abundant feedstock for biological transformation to ethanol, however, its industrial processing needs further improvements to enhance efficiency and cost-effectiveness. In the present study, a low-cost catalyst (CC-SO3H) was synthesized by partial carbonization and sulfonation of crystalline cellulose, which was thermally stable and reactive at 160 °C in 5 times repeated batch of thermohydrolysis of cassava starch. The catalyst was studied for its potential role in the hydrolysis of cassava starch as a standard feedstock. It was shown that the milling of cassava starch in the presence of the CC-SO3H catalyst improved the solid-state reaction that enhanced porosity, increased surface area and decreased crystallinity of the starch granules. These phenomena caused the rapid thermohydrolysis of starch with an exceptionally high starch conversion rate (96.43%), glucose yield (93.12%), and glucose selectivity (95.32%) within 2 h of reaction at 160 "C, 10 bar. The highest ethanol yield (0.43 g ethanol/g total reducing sugars) was achieved at 96 h of fermentation corresponding to the highest ethanol concentration of 15.41 g/L from the fermentation of hydrolysate of mixed-milling/thermo-hydrolysis at 160 C for 2 h of cassava starch. In addition, the reaction kinetics showed the feasibility of this process for robust bioethanol production from starchy feedstocks. [ABSTRACT FROM AUTHOR]

Highlights • Lignocellulosic waste can serve as a microbial carrier in bioconversion processes. • Lignocellulosic carriers were hydrothermally modified for microbial immobilization. • Specific surface area and porosity of corn stalks were improved by the modification. • Conditions of 200 °C for 20 min with a 1 cm size were optimal for modifying the carriers. • Modified carriers showed better immobilization and ethanol fermentation performance. Abstract Microbial immobilization is a key approach to enhance fermentation performance, especially with the advantages of low costs and the good surface properties of the lignocellulosic wastes, which can serve as natural carriers. This study investigated the capability of hydrothermal modification to improve the physicochemical properties of corn stalk carriers for microbial immobilization. Hydrothermal modification can degrade lignocellulosic structure by dissolving part of the components at different conditions. A temperature of 200 °C for 20 min with a carrier side length of 1 cm were selected as the optimal modification conditions. With these conditions, the specific surface area and porosity of the modified corn stalk carriers were 2.44 m2/g and 0.011 cm3/g, respectively, which were twice the values of untreated carriers. Immobilization tests showed that bacteria and yeast grew stably inside the modified carriers and that the immobilized biomass was 49% greater than that of the untreated carriers. After fermentation with bacteria, ethanol production in the modified carrier system was increased by 57% and 99% compared to the untreated carrier system and free bacteria, respectively. These findings confirmed that hydrothermal modification is efficient to improve lignocellulosic carrier properties to achieve better immobilization and fermentation performance, thus benefiting to the utilization of lignocellulosic wastes and their bioconversion processes. [ABSTRACT FROM AUTHOR]

Lignocellulosic materials are good feedstocks for ethanol production. Mathematical models give information about kinetic-metabolic nature of fermentation. The objectives of this study were to determine the chemical composition of non-detoxified tea processing waste hydrolysate (ND-TPWH) and detoxified tea processing waste hydrolysate (D-TPWH), to generate the ethanol from the D-TPWH, and to model the ethanol fermentation in D-TPWH using models including modified Gompertz, re-modified Gompertz, modified logistic, re-modified logistic, modified Richards, re-modified Richards, Stannard, Baranyi, Weibull, and Morgan-Mercer-Flodin. Results indicated that 11.91% of d -glucuronic acid, 7.28% of acetic acid, 98.12% of hydroxymethylfurfural, and 76.88% of phenolics were adsorbed by detoxification process. Ethanol yields by Saccharomyces cerevisiae and Scheffersomyces stipitis (ATCC 58784 and ATCC 58785) were 35.9, 38.98, and 33.87%, respectively. Regarding modeling, depending on the model comparison results including root-mean-square-error, mean-absolute-error, and regression coefficient, the experimental data of ethanol production and sugar consumption were successfully forecasted using Baranyi and Weibull models for S. cerevisiae ; using Morgan-Mercer-Flodin model for S. stipitis (ATCC 58784); and using Stannard model for S. stipitis (ATCC 58785), respectively. Consequently, this was the first report on the ethanol production from D-TPWH and its modeling. TPW can be a good feedstock for ethanol production by the xylose-fermenting yeasts. Suitable flexible models could be applied for more progress of ethanol production process in D-TPWH. [ABSTRACT FROM AUTHOR]

Background: Multiple lignocellulose-derived inhibitors represent great challenges for bioethanol production from lignocellulosic materials. These inhibitors that are related to the levels of intracellular reactive oxidative species (ROS) make oxidoreductases a potential target for an enhanced tolerance in yeasts. Results: In this study, the thioredoxin and its reductase from Kluyveromyces marxianus Y179 was identified, which was subsequently achieved over-expression in Saccharomyces cerevisiae 280. In spite of the negative effects by expression of thioredoxin gene (KmTRX), the thioredoxin reductase (KmTrxR) helped to enhance tolerance to multiple lignocellulose- derived inhibitors, such as formic acid and acetic acid. In particular, compared with each gene expression, the double over-expression of KmTRX2 and KmTrxR achieved a better ethanol fermentative profiles under a mixture of formic acid, acetic acid, and furfural (FAF) with a shorter lag period. At last, the mechanism that improves the tolerance depended on a normal level of intracellular ROS for cell survival under stress. Conclusions: The synergistic effect of KmTrxR and KmTRX2 provided the potential possibility for ethanol production from lignocellulosic materials, and give a general insight into the possible toxicity mechanisms for further theoretical research. [ABSTRACT FROM AUTHOR]

Forward osmosis (FO), driven by high osmotic pressure, was used for the first time for bioethanol production from lignocellulosic biomass. A commercial membrane, TFC-ES (Hydration Technology Innovation), was used and 3.6 M triethylamine (TEA) was chosen as the draw solution because the concentration ratio against a model xylose solution was similar to that achieved with 2.5 M NaCl. The liquid fraction of hot-water-pretreated rice straw was concentrated by using the FO membrane. The initial sugar concentration of 199 mM increased to 825 and 1612 mM after 48 and 72 h of FO concentration, respectively, and these values were much higher than those obtained from nanofiltration. Simultaneous saccharification and fermentation of the liquid fraction after 48 h of FO concentration by xylose-fermenting recombinant Saccharomyces cerevisiae produced 17.7 g/L of ethanol after 24 h fermentation. Thus, the FO process has tremendous potential to up-concentrate sugars obtained from lignocellulosic biomass. [ABSTRACT FROM AUTHOR]

An oxidative production process of xylonic acid using xylose in distillation stillage of cellulosic ethanol fermentation broth was designed, experimentally investigated, and evaluated. Dry dilute acid pretreated and biodetoxified corn stover was simultaneously saccharified and fermented into 59.80 g/L of ethanol (no xylose utilization). 65.39 g/L of xylose was obtained in the distillation stillage without any concentrating step after ethanol was distillated. Then the xylose was completely converted into 66.42 g/L of xylonic acid by Gluconobacter oxydans . The rigorous Aspen Plus modeling shows that the wastewater generation and energy consumption was significantly reduced comparing to the previous xylonic acid production process using xylose in pretreatment liquid. This study provided a practical process option for xylonic acid production from lignocellulose feedstock with significant reduction of wastewater and energy consumption. [ABSTRACT FROM AUTHOR]

Most of ethanol production processes are limited by lower ethanol production rate and recyclability problem of ethanologenic organism. In the present study, immobilized co-fermenting Saccharomyces cerevisiae GSE1618 was employed for ethanol fermentation using rice straw enzymatic hydrolysate in a packed bed reactor (PBR). The immobilization of S . cerevisiae was performed by entrapment in Ca-alginate for optimization of ethanol production by varying alginic acid concentration, bead size, glucose concentration, temperature and hardening time. Remarkably, extra hardened beads (EHB) immobilized with S . cerevisiae could be used up to repeated 40 fermentation batches. In continuous PBR, maximum 81.82 g L −1 ethanol was obtained with 29.95 g L −1 h −1 productivity with initial glucose concentration of 180 g L −1 in feed at dilution rate of 0.37 h −1 . However, maximum ethanol concentration of 40.33 g L −1 (99% yield) with 24.61 g L −1 h −1 productivity was attained at 0.61 h −1 dilution rate in fermentation of un-detoxified rice straw enzymatic hydrolysate (REH). At commercial scale, EHB has great potential for continuous ethanol production with high productivity using lignocellulosic hydrolysate in PBR. [ABSTRACT FROM AUTHOR]

This paper evaluated the effectiveness of nitric acid pretreatment on the hydrolysis and subsequent fermentation of Jerusalem artichoke stalks (JAS). Jerusalem artichoke is considered a potential candidate for producing bioethanol due to its low soil and climate requirements, and high biomass yield. However, its stalks have a complexed lignocellulosic structure, so appropriate pretreatment is necessary prior to enzymatic hydrolysis, to enhance the amount of sugar that can be obtained. Nitric acid is a promising catalyst for the pretreatment of lignocellulosic biomass due to the high efficiency with which it removes hemicelluloses. Nitric acid was found to be the most effective catalyst of JAS biomass. A higher concentration of glucose and ethanol was achieved after hydrolysis and fermentation of 5% (w/v) HNO3-pretreated JAS, leading to 38.5 g/L of glucose after saccharification, which corresponds to 89% of theoretical enzymatic hydrolysis yield, and 9.5 g/L of ethanol. However, after fermentation there was still a significant amount of glucose in the medium. In comparison to more commonly used acids (H2SO4 and HCl) and alkalis (NaOH and KOH), glucose yield (% of theoretical yield) was approximately 47–74% higher with HNO3. The fermentation of 5% nitric-acid pretreated hydrolysates with the absence of solid residues, led to an increase in ethanol yield by almost 30%, reaching 77–82% of theoretical yield.

This study reported a new solution of lignocellulose feedstock storage based on the distributed pretreatment concept. The dry dilute sulfuric acid pretreatment (DDAP) was conducted on corn stover feedstock, instead of ammonia fiber explosion pretreatment. Then the dry dilute acid pretreated corn stover was stored for three months during summer season with high temperature and humidity. No negative aspects were found on the physical property, composition, hydrolysis yield and ethanol fermentability of the long term stored pretreated corn stover, plus the additional merits including no chemicals recovery operation, anti-microbial contaminant environment from stronger acid and inhibitor contents, as well as the mild and slow hydrolysis in the storage. The new pretreatment method expanded the distributed pretreatment concept of feedstock storage with potential for practical application. [ABSTRACT FROM AUTHOR]

Effects of switchgrass particle sizes (<0.25 mm, 0.5–1.0 mm, and 2.0–4.0 mm) on the effectiveness of H 2 SO 4 and NaOH pretreatments were investigated. As particle size increased, glucan, xylan, and lignin contents in raw switchgrass augmented from 30.32% to 32.02%, 18.44% to 19.03%, and 14.78% to 15.33%, respectively. Glucan and xylan (58.54–60.94% and 18.55–20.01%) contents in NaOH pretreated switchgrass and their recoveries (91.95–94.69% and 47.91–52.31%) increased. The highest glucan content (55.76%) and recovery (79.72%) in H 2 SO 4 pretreated switchgrass were reached by middle particle size. The lowest (59.39% for H 2 SO 4 and 58.99% for NaOH) and highest (65.23% for H 2 SO 4 and 66.15% for NaOH) CrI values were obtained from middle and small particle sizes, respectively. SEM images and FTIR spectra showed no visible variations in microstructures and chemical bonds among different particle sizes under the same pretreatment conditions. On the basis of pretreated switchgrass, the highest ethanol concentration and efficiency were reached by big particle size for H 2 SO 4 pretreated (7.03 g/L and 49.28%) switchgrass, while they were achieved by small particle size for NaOH pretreated (11.68 g/L and 72.37%) switchgrass. The highest ethanol yield based on raw switchgrass was attained by big particle size for untreated (29.54%), middle particle size for H 2 SO 4 pretreated (30.60%), and small particle size for NaOH pretreated (62.36%) switchgrass. These findings indicate that the optimal ethanol conversion performance is the result of the interaction between the pretreatment method and biomass particle size. • The effect of biomass particle size on cellulosic ethanol production was investigated. • Glucan, xylan, and lignin contents in raw switchgrass increased as particle size increased. • SEM and FTIR spectra showed no visible variations among different biomass particle sizes. • Biomass particle size has a significant influence on ethanol concentration and yield. [ABSTRACT FROM AUTHOR]

ABSTRACT Corncob residue as the lignocellulosic biomass accumulated phenolic compounds generated from xylitol production industry. For utilization of this biomass, Zymomonas mobilis ZM4 was tested as the ethanol fermenting strain and presented a better performance of cell growth (2.8 × 108 CFU/mL) and ethanol fermentability (54.42 g/L) in the simultaneous saccharification and fermentation (SSF) than the typical robust strain Saccharomyces cerevisiae DQ1 (cell growth of 2.9 × 107 CFU/mL, ethanol titer of 48.6 g/L). The physiological response of Z. mobilis ZM4 to the twelve typical phenolic compounds derived from lignocellulose was assayed and compared with that of S. cerevisiae DQ1. Z. mobilis ZM4 showed nearly the same tolerance to the phenolic aldehydes with S. cerevisiae DQ1, but the stronger tolerance to the phenolic acids existing in corncob residue (2-furoic acid, p-hydroxybenzoic acid, p-coumaric acid, vanillic acid, ferulic acid, and syringic acid). The tolerance mechanism of Z. mobilis was investigated in terms of inhibitor degradation, cell morphology and membrane permeability under the stress of phenolics using GC-MS, scanning and transmission electron microscopies (SEM and TEM), as well as fluorescent probes. The results reveal that Z. mobilis ZM4 has the capability for in situ detoxification of phenolic aldehydes, and the lipopolysaccharide aggregation on the cell outer membrane of Z. mobilis ZM4 provided the permeable barrier to the attack of phenolic acids. Biotechnol. Bioeng. 2015;112: 1770-1782. © 2015 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Commercialization of lignocellulosic ethanol fermentation requires its high titer, but the reactive oxygen species (ROS) accumulation during the bioprocess damaged the cells and compromised this goal. To improve the cellular anti-oxidative activity during non-detoxified corncob residue hydrolysate fermentation, seed cells were prepared to possess a higher level of intracellular biotin pool (IBP), which facilitated the biosyntheses of catalase and porphyrin. As a result, the catalase activity increased by 1.3-folds compared to control while the ROS level reduced by 50%. Cell viability in high-IBP cells was 1.7-folds of control and the final ethanol titer increased from 31.2 to 41.8 g L −1 in batch fermentation. The high-IBP cells were further used for repeated-batch fermentation in the non-detoxified lignocellulosic hydrolysate, and the highest titer and average productivity of ethanol reached 63.7 g L −1 and 1.2 g L −1 h −1 . The results were favorable to future industrial application of this lignocellulosic bioethanol process. [ABSTRACT FROM AUTHOR]

The cost effective production of cellulolytic enzymes and their use for generating higher reducing sugars from lignocellulosic biomass is critical for attaining the commercial viability of lignocellulosic biofuels production. Optimizing the use of locally available agroresidues and natural nutritional alternatives for fungal growth and enzyme production can reduce the cost of enzyme production. In the present work, maximum cellulolytic activity of 30.85 IU/gds was obtained from Trichoderma reesei NCIM 1186 using wheat bran as the substrate and coconut water as the nutritional supplement. The produced cellualse was used for enzymatic saccharification of phosphoric acid pretreated wheat straw. The enzymatic sachharification was optimized through central composite design (CCD) based response surface methodology (RSM). Maximum reducing sugar yields of 371.44 mg/g dry substrate were obtained at 18% (w/v) substrate concentration, 50°C and 24 h of incubation time. Further, the saccharified sugar hydrolysate was fermented using S. cerevisiae NCIM 3215. Maximum ethanol production (2.58% w/v) obtained after 24 h of fermentation at 30°C. © 2015 American Institute of Chemical Engineers Environ Prog, 34: 1243-1248, 2015 [ABSTRACT FROM AUTHOR]

The research was carried out with the aim to determine the impact of the application of the fed-batch system of simultaneous saccharification and fermentation of polysaccharides contained in rape straw on the production of ethanol in SSF system. Rape straw after alkaline pretreatment was subjected to detoxification by double rinsing with water. After 24 and 48 hours of simultaneous hydrolysis and fermentation, pretreated and dried substrate was added to the samples, each in an amount of 25% of the initial amount of substrate in the slurry. Comparatively simultaneous hydrolysis and fermentation without additional supply of substrate was carried out. The effects of the fermentation were expressed as the amount of ethanol produced in a fermentation medium. In the control experiment of hydrolysis and fermentation 1.60% (v/v) of ethanol was obtained. However, in the fed-batch system, ethanol concentration was 1.81% (v/v), which represented an increase in ethanol concentration of 13%. [ABSTRACT FROM AUTHOR]

Process control automation in the emerging biorefinery industry may be achieved by applying effective methods for monitoring compound concentrations during the production processes. This study examines the application of Raman spectroscopy with an excitation wavelength of 785 nm and an immersion probe for in situ monitoring the progression of pretreatment, hydrolysis and fermentation processes in the production of lignocellulosic ethanol. Raman signals were attenuated by light scattering cells and lignocellulosic particulates, which the quantification method to some degree could correct for by using an internal standard in the spectra. Allowing particulates to settle by using a slow stirring speed further improved results, suggesting that Raman spectroscopy should be used in combination with continuous separation when used to monitor process mixtures with large amounts of particulates. The root mean square error of prediction (RMSE) of ethanol and glucose measured in real-time was determined to be 0.98 g/L and 1.91 g/L respectively. [ABSTRACT FROM AUTHOR]

Xylose is abundant in lignocellulosic biomass. The fermentation of xylose is still a key problem in cellulose ethanol fermentation. In this research, the xylose fermentation strains were isolated from the soil sample. Strain N6 was chosen for further xylose fermentation experiments. Comparison of its 16S rDNA gene sequence with available sequences in GenBank showed that it was 100 % identical to that of Bacillus cereus strain SWFU2816 (Accession No. JN935015.1). Strain N6, which ferments xylose and hexose to ethanol, can produce fuel ethanol. The ability of strain N6 to transform xylose was better than its ability to transform glucose. As a result, the optimal condition for xylose fermentation was determined. The optimum fermentation conditions at 150 rpm for 48 h in a shake flask were as follows: pH 7.0, reducing sugar 70 g L-1, inoculation amount 5 %, and temperature 38 °C. The xylose to ethanol yield coefficient could reach a maximum of 0.26 g g-1. At the same time, the influence of the acid hydrolysis by-products on the isolated strain was studied. Compared to the commonly used saccharomycetes, the tolerance of strain N6 on furaldehyde had greatly improved, which could help ethanol fermentation from lignocellulose materials. [ABSTRACT FROM AUTHOR]

Amaranthus is a fast-growing perennial plant containing large amounts of extractable green proteins and lignocellulose residues. However, it remains to explore optimal Amaranthus biomass process technology for biofuel production. In this study, we examined that mild alkali and acid pretreatments (1% NaOH, 2% H 2 SO 4) were sufficient for near-complete biomass enzymatic saccharification, while 8% Amaranthus endogenous proteins were supplemented into the enzymatic hydrolyses. By performing classic yeast fermentation with all carbon sources from directly-extractable sugars and starch and lignocellulose enzymatic hydrolysis, this work achieved the bioethanol yield up to 23.5% (% dry matter). Notably, with respect to extremely high yield of Amaranthus straw, the maximum bioethanol yield was estimated at 14.46 t/ha/year, which was much higher than those of other major bioenergy crops as previously reported. Furthermore, this work proposed a hypothetic model to elucidate how the complete biomass saccharification was achieved to maximize bioethanol production at large scale, based on the effective wall polymer extraction and distinct lignocellulose feature modification for remarkably enhanced biomass porosity and cellulases adsorption. Hence, this work has demonstrated that Amaranthus could be applied as a novel and leading bioenergy crop, providing a powerful strategy for optimal biomass processing towards high bioethanol production. [Display omitted] • Amaranthus plant is a promising bioenergy crop rich at digestible lignocellulose. • Amaranthus straw was of extractable hemicellulose-lignin complexes. • Endogenous proteins let to 97–99% biomass saccharification with Amaranthus. • Bioethanol yield of 23.47 g/100 g was obtained with Amaranthus straw. [ABSTRACT FROM AUTHOR]

Highlights: [•] Biomass pelleting is an effective biomass densification method required for biofuels production. [•] Biomass pelleting leads to partial deconstruction of the complex biomass structure and facilitates bioethanol production. [•] Pelleting process led to better enzymatic hydrolysis of pretreated biomasses without affecting the quality of sugars for fermentation. [•] Ethanol yield on the basis of released sugars did not differ significantly between pelleted and unpelleted samples. [•] Schematic diagram for complete utilization of lignocellulosic biomass is proposed. [Copyright &y& Elsevier]

Ethanol fermentation from food wastes containing mainly starch without carrying out sterilization was investigated by using wild and tolerant yeast, Issatchenkia orientalis MF-121. The MF-121 strain is not a suitable choice for ethanol fermentation from lignocellulosic biomass because it is only capable of fermenting hexoses of glucose, mannose, and fructose to ethanol. Therefore, we first isolated acid- and salt-tolerant yeast that are capable of fermenting various monosaccharides to ethanol, and the isolated yeast that showed the ability to ferment ethanol from glucose, mannose, galactose, fructose, and xylose, was identified as Zygoascus hellenicus LK-5G on the basis of the 26S rRNA sequence analysis. [Copyright &y& Elsevier]

Abstract: A small solar energy collector was run to heat lignocellulosic hydrolyzates through an exchanger, and the heated hydrolyzate was concentrated by vacuum membrane distillation (VMD). Under optimal conditions of velocity of 1.0m/s and 65°C, glucose rejection was 99.5% and the flux was 8.46Lm−2 h−1. Fermentation of the concentrated hydrolyzate produced 2.64 times the amount of ethanol as fermentation using the original hydrolyzate. The results of this work indicated the possibility to decrease the thermal energy consumption of lignocellulosic ethanol through using VMD. [Copyright &y& Elsevier]

In this work, forage sorghum biomass was studied as feedstock for ethanol production by a biological conversion process comprising the steps of hydrothermal steam explosion pretreatment, enzymatic hydrolysis with commercial enzymes, and fermentation with the yeast Saccharomyces cerevisiae. Steam explosion conditions were optimized using a response surface methodology considering temperature (180-230°C) and time (2-10 min). Sugar recovery in the pretreatment and the enzymatic digestibility of the pretreated solid were used to determine the optimum conditions, i.e., 220°C and 7 min. At these conditions, saccharification efficiency attained 89 % of the theoretical and the recovery of xylose in the prehydrolyzate accounted for 35 % of the amount of xylose present in raw material. Then, a simultaneous hydrolysis and fermentation (SSF) process was tested at laboratory scale on the solid fraction of forage sorghum pretreated at optimum condition, in order to evaluate ethanol production. The effect of the enzyme dose and the supplementation with xylanase enzyme of the cellulolytic enzyme cocktail was studied at increasing solid concentration up to 18 % ( w/ w) in SSF media. Results show good performance of SSF in all consistencies tested with a significant effect of increasing enzyme load in SSF yield and final ethanol concentration. Xylanase supplementation allows increasing solid concentration up to 18 % ( w/ w) with good SSF performance and final ethanol content of 55 g/l after 4-5 days. Based on this result, about 190 l of ethanol could be obtained from 1 t of untreated forage sorghum, which means a transformation yield of 85 % of the glucose contained in the feedstock. [ABSTRACT FROM AUTHOR]

Abstract: Using standard laboratory equipment, thermochemically pretreated oat straw was enzymatically saccharified and fermented to ethanol, and after removal of ethanol the remaining material was subjected to biogas digestion. A detailed mass balance calculation shows that, for steam explosion pretreatment, this combined ethanol fermentation and biogas digestion converts 85–87% of the higher heating value (HHV) of holocellulose (cellulose and hemicellulose) in the oat straw into biofuel energy. The energy (HHV) yield of the produced ethanol and methane was 9.5–9.8MJ/(kg dry oat straw), which is 28–34% higher than direct biogas digestion that yielded 7.3–7.4MJ/(kg dry oat straw). The rate of biogas formation from the fermentation residues was also higher than from the corresponding pretreated but unfermented oat straw, indicating that the biogas digestion could be terminated after only 24days. This suggests that the ethanol process acts as an additional pretreatment for the biogas process. [Copyright &y& Elsevier]

Abundant plant biomass has the potential to become a sustainable source of fuels and chemicals. Realizing this potential requires the economical conversion of recalcitrant lignocellulose into useful intermediates, such as sugars. We report a high-yielding chemical process for the hydrolysis of biomass into monosaccharides. Adding water gradually to a chloride ionic liquid-containing catalytic acid leads to a nearly 90% yield of glucose from cellulose and 70-80% yield of sugars from untreated corn stover. Ion-exclusion chromatography allows recovery of the ionic liquid and delivers sugar feedstocks that support the vigorous growth of ethanologenic microbes. This simple chemical process, which requires neither an edible plant nor a cellulase, could enable crude biomass to be the sole source of carbon for a scalable biorefinery. [ABSTRACT FROM AUTHOR]

Abstract: Yeast strains of Saccharomyces cerevisiae have been extensively studied in recent years for fuel ethanol production, in which yeast cells are exposed to various stresses such as high temperature, ethanol inhibition, and osmotic pressure from product and substrate sugars as well as the inhibitory substances released from the pretreatment of lignocellulosic biomass. An in-depth understanding of the mechanism of yeast stress tolerance contributes to breeding more robust strains for ethanol production, especially under very high gravity conditions. Taking advantage of the “omics” technology, the stress response and defense mechanism of yeast cells during ethanol fermentation were further explored, and the newly emerged tools such as genome shuffling and global transcription machinery engineering have been applied to breed stress resistant yeast strains for ethanol production. In this review, the latest development of stress tolerance mechanisms was focused, and improvement of yeast stress tolerance by both random and rational tools was presented. [Copyright &y& Elsevier]

The article presents a study on the properties of ethanol fermentation by basidiomycetes to determine its suitability for consolidated bioprocessing (CBP) by Flammulina velutipes. Basidiomycetes can degrade lignocellulosic biomass and produce alcohol dehydrogenase which may be useful for direct production of ethanol from lignocellulose. Methods used include inoculum preparation for fermentation, and measurement of ethanol. Results show advantageous characteristics of F. velutipes for CBP.

Conversion of organic wastes to methane via anaerobic digestion has been practiced for more than 160 years. However, the technical bottlenecks derived from the thermodynamic limitations of interspecies hydrogen/formate transfer (IHT/IFT) between syntrophs and methanogens resulting in the slow fermentation rate, low methane conversion efficiency and poor stability of system still limit its large-scale application. No engineering strategy to speed up IHT/IFT for dramatically changing the performances of anaerobic digestion has been developed. However, recent studies documented that simply pretreating organic wastes to produce ethanol could effectively accelerate and stabilize anaerobic digestion. This may be linked to the promotion of direct interspecies electron transfer (DIET), an alternative working mode that no longer requires hydrogen or formate as an electron carrier. Further information on how this strategy affects the function of methanogenic communities to clarify its advantages is required. In this study, we summarized the evidence that pretreating organic wastes to produce ethanol enhanced anaerobic digestion, discussed the link between ethanol and DIET, and emphasized how this strategy would be better applied in the future. [Display omitted] • Evidence that ethanol-type fermentation enhanced anaerobic digestion was summarized. • Link between ethanol and direct interspecies electron transfer was discussed. • Engineering a better anaerobic digestion by ethanol-type fermentation was emphasized. [ABSTRACT FROM AUTHOR]

Abstract: Antarctic basidiomycetous yeast Mrakia blollopis SK-4 has unique fermentability for various sugars under a low temperature condition. Hence, this yeast was used for ethanol fermentation from glucose and also for direct ethanol fermentation (DEF) from cellulosic biomass without/with Tween 80 at 10°C. Maximally, 48.2g/l ethanol was formed from 12% (w/v) glucose. DEF converted filter paper, Japanese cedar and Eucalyptus to 12.2g/l, 12.5g/l and 7.2g/l ethanol, respectively. In the presence of 1% (v/v) Tween 80, ethanol concentration increased by about 1.1–1.6-fold compared to that without Tween 80. This is the first report on DEF using cryophilic fungi under a low temperature condition. We consider that M. blollopis SK-4 has a good potential for ethanol fermentation in cold environments. [Copyright &y& Elsevier]

The present study emphasized on ethanol production using biologically synthesized ZnO nanoparticles as a catalyst. Fusarium oxysporum has been shown to have a high zinc metal tolerance ability and a potential for extracellular synthesis of ZnO nanoparticles. The purity and quality of synthesized nanoparticles were confirmed by various characterization methods such as UV–Vis spectroscopy, FTIR, XRD, SEM, TGA and DTA analysis. Primarily, for bioethanol production the rice straw was subjected to delignification by ammonia. Enzymes required for further degradation of lignocellulosic biomass of rice straw into monosaccharide sugars was produced using fungus Fusarium oxysporum. These sugars were then converted into ethanol via fermentation under micro-aerobic conditions. Ethanol yield was enhanced by using zinc oxide nanoparticles in certain concentration range during fermentation. Maximum ethanol yield of 0.0359 g/g of dry weight based plant biomass was obtained at 200 mg/L concentration of ZnO nanoparticles. Here, we summarizes the synthesis and recent advances of ZnO nanoparticles in bioethanol production which in turn will be used in various industrial applications, pharmaceutical sector and also as a bio-fuel. Image 1 • Zinc oxide nanoparticles were synthesized from fungus Fusarium oxysporum. • Bioethanol was produced from rice straw using fungus Fusarium oxysporum. • Zinc oxide nanoparticles enhances the concentration of bioethanol from rice straw. • Maximum 0.0359 g/g of ethanol was produced at 200 mg/L of zinc oxide nanoparticles. [ABSTRACT FROM AUTHOR]

• Feasibility of using waste pizza for ethanol fermentation was examined. • Enzymatic hydrolysis of WP by α-amylase could be completed within 50 min. • The total power consumed for the whole bio-process was 1.1 kW⋅h. • The highest ethanol yield of 0.292 g/g WP was obtained. • This is the first study to report bio-ethanol production from WP. In this work, the feasibility of ethanol production from waste pizza (WP) by enzymatic hydrolysis and fermentation was investigated. The effects of enzyme volumes (0.02-0.08 mL/L) and WP mass ratios (50−160 g/L) on the performance of enzymatic hydrolysis and ethanol fermentation were also examined. It was observed that the lowest enzyme volume (0.02 mL/L) could completely hydrolyze WP with mass ratio of 50 g/L. The reducing sugar (RS) increased obviously with increasing of WP mass ratio from 50 g/L to 160 g/L when the enzyme volume of 0.02 mL/L was applied. The WP hydrolysate was utilized as substrate for bio-ethanol production with the highest cumulative ethanol production of 27.58 g/L and ethanol yield of 0.292 g/g WP, respectively. To our knowledge, this is the first study to report ethanol production from WP by enzymatic hydrolysis and fermentation. [ABSTRACT FROM AUTHOR]

• Higher loading operation in AnMBR systems via EP for starch-rich artificial FW. • Three-fold higher enabled OLR 26.5 g-COD/L/d in EP series than the control series. • Acetic acid majorly constituted VFA in the EP series' reactor. • EP caused high loading operation by avoiding pH decrease. • Based on the Gibbs free energy, biomethanation of EP is easier to conduct. The study aims to examine whether ethanol fermentation pretreatment (EP) of food waste can contribute to high load operation on methane fermentation using an anaerobic membrane bioreactor (AnMBR). The hydraulic retention time was reduced stepwise from 20 to 5 days to increase the load by increasing the feeding volume. The corresponding organic loading rate (OLR) ranged from 6.6 to 26.5 g-COD/L/day. The control series (without pretreatment) was operable to an OLR of 8.8 g-COD/L/day versus 26.5 g-COD/L/day for the EP series. In the control series, the major volatile fatty acid (VFA) produced by acidogenesis in the reactor was propionic acid because based on Gibbs free energy variations for the methane conversion, acetic acid conversion was not as easy as from propionic acid as from ethanol in the EP series. EP proved effective in avoiding VFA accumulation and subsequent decreased pH. Therefore, EP significantly improves AnMBR performance. [ABSTRACT FROM AUTHOR]

Raman spectroscopy as a process analytical technology tool was implemented for the monitoring and control of ethanol fermentation carried out with Saccharomyces cerevisiae. The need for the optimization of bioprocesses such as ethanol production, to increase product yield, enhanced the development of control strategies. The control system developed by the authors utilized noninvasive Raman measurements to avoid possible sterilization problems. Real‐time data analysis was applied using partial least squares regression (PLS) method. With the aid of spectral pretreatment and multivariate data analysis, the monitoring of glucose and ethanol concentration was successful during yeast fermentation with the prediction error of 4.42 g/L for glucose and 2.40 g/L for ethanol. By Raman spectroscopy‐based feedback control, the glucose concentration was maintained at 100 g/L by the automatic feeding of concentrated glucose solution. The control of glucose concentration during fed‐batch fermentation resulted in increased ethanol production. Ethanol yield of 86% was achieved compared to the batch fermentation when 75% yield was obtained. The results show that the use of Raman spectroscopy for the monitoring and control of yeast fermentation is a promising way to enhance process understanding and achieve consistently high production yield. [ABSTRACT FROM AUTHOR]

Sweet sorghum juice, a potential bioethanol feedstock, can be incorporated into the dry-grind ethanol process to improve sugar utilization efficiency, thereby enhancing ethanol yields. The juice is normally obtained by pressing the stalk through roller mills in tandem. Juice extraction by this process is known to be labor intensive, less efficient, and susceptible to considerable fermentable sugar loss due to microbial activities when stored at room temperature. Sweet sorghum juice extraction via diffusion has recently been proposed to improve sugar recovery efficiency. In this study, extraction kinetics based on the optimized diffusion parameters (8% grain loading, 85 °C, and 120 min) were determined to describe the mass transfer of sugars in sweet sorghum biomass during the diffusion process. Diffusion parameters obtained from previous studies were used to extract free sugars and convert them into ethanol using granular starch hydrolyzing enzymes (GSHE) and traditional enzymes. Ethanol yields at 72 h of fermentation mashes treated with GSHE and those with traditional enzymes were comparable (14.49–14.56%, v/v). Ethanol fermentation efficiencies also ranged from 88.92–92.02%. [ABSTRACT FROM AUTHOR]