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The study aims to enhance ethanol production by Wickerhamomyces subpelliculosus ZE75 isolated from marine sediment. In addition, analyzing the kinetic parameters of ethanol production and optimization of the fermentation conditions was performed. The marine yeast isolate ZE75 was selected as the front runner ethanol-producer, with an ethanol yield of 89.77 gL−1. ZE75 was identified relying on the phenotypic and genotypic characteristics of W. subpelliculosus. The genotypic characterization based on the Internal Transcribed Spacer (ITS) sequence was deposited in the GenBank database with the accession number OP715873. The maximum specific ethanol production rate (vmax) was 0.482 gg−1 h−1 at 175 gL−1 glucose concentration, with a high accuracy of R2 0.95. The maximum growth specific rates (μmax) were 0.141 h−1 obtained at 150 gL−1 glucose concentration with R2 0.91. Optimization of the fermentation parameters such as pH and salinity has been achieved. The highest ethanol yield 0.5637 gg−1 was achieved in a 100% natural seawater-based medium. The maximum ethanol production of 104.04 gL−1 was achieved at pH 4.5 with a specific ethanol rate of 0.1669 gg−1 h−1. The findings of the present study recommend the possibility of ethanol production from a seawater-based medium on a large scale using W. subpelliculosus ZE75. [ABSTRACT FROM AUTHOR]

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]

The excess of minerals in the industrial substrates is detrimental for Saccharomyces cerevisiae ethanol fermentation performance. In this work, we sought to understand the effect of some of those minerals on the physiology of Dekkera bruxellensis. Three groups of minerals were classified on the basis of the aerobic growth profiles on glucose neutrals (K+, Mg2+, P5+, and Zn2+), inducers (Mn2+ and Ca2+), and inhibitors (Al3+, Cu2+, and Fe2+). Cu2+ showed the highest mineral toxicity, and its effect was dependent on the level of medium aeration. On the other hand, copper stimulated respiration by increasing growth on respiratory carbon sources. Most growth inhibitors also hampered glucose fermentation, with changes in carbon distribution to metabolic routes dedicated to anabolic reactions and for alternative reduced cofactors oxidations to maintain cellular homeostasis. The negative effect of Cu2+ on yeast fermentation was partially alleviated by Mg2+ and Mn2+, similar to magnesium antagonism observed for S. cerevisiae. All these results might contribute to understand the action of these minerals in sugarcane substrates on the physiology of D. bruxellensis cells. Therefore, it represents one more step for the consolidation of the industrial use of this yeast in the production of fuel ethanol as well as other biotechnological goods. [ABSTRACT FROM AUTHOR]

Wood biomass conversion for fossil resource replacement could result in the sustainable production of chemicals, although lignin represents an obstacle to efficient polysaccharide use. White-rot fungus Phlebia sp. MG-60 reportedly selectively and aerobically degrades lignin in hardwood, then it begins cellulose saccharification from the delignified wood to produce ethanol. Environmental conditions might change white-rot fungi-driven biomass conversion. However, how the environmental response sensor affects ethanol fermentation in white-rot fungi remains elusive. In this study, we focused on MGHOG1, the yeast Hog1 homolog in Phlebia sp. MG-60, a presumably important player in osmoresponse. We generated MGHOG1 overexpressing (OE) transformants in Phlebia sp. MG-60, exhibiting slower mycelial growth compared with the wild-type under salinity stress. MGHOG1 overexpressing liquid cultures displayed suppressed mycelial growth and ethanol fermentation. Therefore, MGHOG1 potentially influences ethanol fermentation and mycelial growth in Phlebia sp. MG-60. This study provides novel insights into the regulation of white-rot fungi-mediated biomass conversion. [ABSTRACT FROM AUTHOR]

The present study demonstrates the feasibility of a two-phase biorefinery process applied to waste substrates producing ethanol rich effluents. The process includes a dark fermentation step followed by photo fermentation and it is able to optimize hydrogen production from waste biomass. The study was conducted using winery wastewater as feedstock. The results indicate that no additional treatments are required when an appropriate dilution of the initial waste is applied. Microbial consortia contained in the winery wastewater promoted a fermentative ethanol pathway. The ethanol rich effluent was converted into hydrogen by phototrophic microorganisms. Despite the presence of inhibiting compounds, the adoption of a mixed phototrophic culture allowed to obtain good results in terms of hydrogen production. Specifically, up to 310 mLH 2 gCOD consumed −1 were obtained in the photo fermentative stage. The effectiveness of ethanol rich dark fermentation effluents for hydrogen production enhancement was demonstrated. Noteworthy, polyhydroxybutyrate was also produced during the experiments. The work faces two of the major challenges in the sequential dark fermentation and photo fermentation technology applied to real waste substrates: the minimization of pre-treatments and the enhancement of the hydrogen production yields using ethanol rich DFEs. [Display omitted] • A dark-photo fermentation process for winery wastewater treatment is proposed. • Indigenous cultures of winery wastewater promote the ethanol production pathway. • Dark fermentation intermediates define the photo fermentative hydrogen yield. • Ethanol rich dark fermentation effluents are effective substrates for PNSB. • Use of mixed PNSB cultures is beneficial to reduce pre-treatments. [ABSTRACT FROM AUTHOR]

Bioethanol is alternative renewable energy typically obtained from glucose through a fermentation process using Saccharomyces cerevisiae. In the bioethanol fermentation process using yeast, there are several inhibiting factors, such as a high concentration of substrate, ethanol as the product, and nutrients. The present study aimed to investigate the effect of fermentation time (12- 72 hours), immobilized carrier size (sizes of 0.5 cm3, 1 cm3, and 1.5 cm3), and medium pH (3.0, 4.0, and 5.0) on the ethanol fermentation process using immobilized yeast in jackfruit (Artocarpus heterophyllus) seeds and subsequently to compare its performance with a free cell system. The highest ethanol concentration (89.15 g/L) with a yield of 96.92% was obtained by immobilizing yeast in jackfruit seed at a fermentation time of 72 hours, carrier size of 0.5 cm3, and medium pH of 5.0. When compared to the free cell system fermentation under identical operating conditions, immobilized yeast in jackfruit seed obtained 1.41 times higher ethanol concentration. Jackfruit seed also led to a higher ethanol concentration compared to other S. cerevisiae carriers. Altogether, our findings imply that jackfruit seed has great potential as a carrier of S. cerevisiae in the process of fermenting glucose into ethanol. [ABSTRACT FROM AUTHOR]

In this study, major factors involved in regulating ethanol production from wood by the saprotrophic white-rot fungus Phanerochaete sordida YK-624 were investigated. P. sordida YK-624 produced ethanol from wood meal culture without the addition of any nutrients, and ethanol was produced from wood culture only when the oxygen concentration in headspace was reduced to ≤5%; thereafter, ethanol production ceased within a few days. Analyses of gene expression during aerobic incubation indicated that P. sordida simultaneously upregulates the glycolytic pathway from sugar uptake to pyruvate conversion during ethanol fermentation and suppresses pyruvate influx into the TCA cycle. Upon termination of ethanol fermentation, the expression of all tested genes was repressed, and the fungus ceased to grow. In contrast, the fungus could utilize ethanol for aerobic growth. These results suggest that ethanol fermentation by P. sordida functions as a short-term stress response system under anaerobic conditions during wood decay, enabling the fungus to rapidly resume growing when oxygen is supplied (e.g., following breakdown of plant cell walls or removal of the fungus from water immersion). This is the first report to describe the physiologic significance of ethanol fermentation in saprotrophic white-rot fungi. [Display omitted] • The biological significance of ethanol fermentation by saprotrophic white-rot fungus P. sordida YK-624 was speculated. • P. sordida YK-624 produced ethanol from wood meal without addition of any nutrients under hypoxic condition. • P. sordida YK-624 could survive and ferment for only a few days under hypoxia conditions during wood decay. • Ethanol fermentation in P. sordida YK-624 appears to be a short-term hypoxia tolerance system. [ABSTRACT FROM AUTHOR]

Bioethanol is an environmentally benign renewable energy commonly obtained from glucose fermentation using Saccharomyces cerevisiae. The purposes of this study are to investigate the effects of time, temperature, pH, immobilized yeast cell loading, beads reuse during ethanol production through batch fermentation of glucose derived from oil palm empty fruit bunches by S. cerevisiae immobilized on Na-alginate beads and to compare the performance of fermentation using immobilized yeast cells and that of using a free cell system. The results revealed that time, temperature, pH, yeast mass and beads reuse significantly affected the ethanol and final glucose concentrations. As expected, a maximum ethanol concentration was obtained from fermentation using immobilized yeast cells at 30 °C, pH 5, and immobilized yeast cell loading of 0.75 g for 48 hours. However, fermentation with a free cell system at the same conditions resulted in lower ethanol yield. The highest ethanol concentration of 88.125 g/L with a productivity of 1.84 g/L·h was achieved from the second cycle fermentation using of immobilized cells beads. The results suggest that an immobilized cell system exhibits great potential applications for improved ethanol production due to its ability to sustain the stability of cell activity, reduce contamination tendency, and protect yeast cells from any possible inhibitions. [ABSTRACT FROM AUTHOR]

Aim: Tyrosol, a quorum sensing molecule in yeasts, was reported to reduce lag phase and induces hyphae formation during cell proliferation. However, evidence of any enhancing effect of tyrosol in cellular proliferation within fermentative environment is unclear. In this investigation, selected yeast cells were assessed for their ability to synthesize tyrosol followed by examining the role of the molecule during fermentation. Methods and Results: Tyrosols were characterized in four fermentative yeasts viz., Saccharomyces cerevisiae, Wickerhamomyces anomalus, Candida glabrata and Candida tropicalis isolated from traditional fermentative cakes of northeast India. All the isolates synthesized tyrosol while C. tropicalis exhibited filamentous growth in response to tyrosols retrieved from other isolates. Purified tyrosols showed protective behaviour in C. tropicalis and S. cerevisiae under ethanol mediated oxidative stress. During fermentation, tyrosol significantly enhanced growth of W. anomalus in starch medium while C. tropicalis exhibited growth enhancement in starch and glucose sources. The chief fermentative yeast S. cerevisiae showed notable enhancement in fermentative capacity in starch medium under the influence of tyrosol con‐commitment of ethanol production. Conclusion: The study concludes that tyrosol exerts unusual effect in cellular growth and fermentative ability of both Saccharomyces and non‐Saccharomyces yeasts. Significance and Impact of the Study: This is the first report of expression of tyrosol by non‐conventional yeasts, where the molecule was found to exert enhancing effect during fermentation, thereby augmenting the process of metabolite production during traditional fermentation. [ABSTRACT FROM AUTHOR]

A two-step pretreatment using sequential dilute acid/alkali was applied in this study to improve the hydrolysis of corncobs. 88.6% of the hemicellulose was selectively removed by dilute sulfuric acid hydrolysis (DA) in the first step, 88% of the lignin was effectively extracted by sodium hydroxide in the second step. Consequently, a high content of glucan (74.4%), corresponding to 94.6% recovery, remained in the pretreated biomass. The substrate enzymatic digestibilities (SED) of the two-step pretreated biomass were 64%, 80%, 91%, and 93% after 72 h hydrolysis with enzyme loadings of 5, 10, 15, and 20 FPU/g substrate, respectively, which were much higher than those of the DA-pretreated material. The ethanol concentration after the simultaneous saccharification and fermentation (SSF) process at 15% (w/w) solids loading reached 52 g/L, equivalent to 77.2% of the theoretical ethanol yield based on an untreated corncobs glucan content. The changes to the chemical and physical structures of the residues detected by SEM, FTIR, and the DPv test were correlated with the improved enzymatic digestibility. [ABSTRACT FROM AUTHOR]

Fuel ethanol has been consolidated in view of the current energy matrix. However, for an efficient process, the yeast and the quality of the substrate used must be taken into account. Thus, this study aims to evaluate sugarcane juice and sweet sorghum and analyze cell viability, ethanol production and the assimilation of amino acids present in these substrates as a function of temperature. The Industrial yeasts Saccharomyces cerevisiae FT858 and Pedra-2 (Pe-2) were activated with pre-inoculum of 2% YPD. The biomass obtained was inoculated on the substrates and incubated at 30 and 40°C at 250 rpm. Aliquots were collected for feasibility analyses with methylene blue, ethanol by gas chromatography and amino acids by high performance liquid chromatography. Yeasts showed better performance in sorghum broth at 30°C. The viability of 89% for Pe-2 and 85% for FT858 and ethanol concentration of 10% (v v-1) for both yeasts. At 40°C there was a reduction in these parameters. Sorghum had the highest amount of amino acids and serine, arginine, alanine and tryptophan were effectively assimilated by yeasts. The temperature of 40°C interfered in the metabolic capacity of the yeasts, causing thermal stress, inducing a greater consumption of amino acids. [ABSTRACT FROM AUTHOR]

[Display omitted] • pflA knockout enhanced ethanol tolerance and production in T. aotearoense SCUT27/ Δldh. • The ethanol/acetate ratio increased 2.16-fold when compared to the parental strain. • Oxidative decarboxylation of pyruvate via Pfor is favorable over Pfl for ethanol production. • Immobilized-cell fermentation was employed to further improve the ethanol production. • The highest ethanol production (45.01 g/L) in T. aotearoense SCUT27 was obtained. Thermophilic anaerobic bacteria have received increasing interest as a promising bioprocessing platform for bioethanol production due to their broad substrate range and higher operating temperature. However, ethanol concentration is still lower than the commercial requirements on account of the high by-product formation and low ethanol tolerance. Our previous transcriptome analysis showed the gene expression level of pyruvate formate lyase-activating protein (PflA) was significantly down-regulated when Thermoanaerobacterium aotearoense SCUT27/ Δldh was stimulated by various concentrations of ethanol. Based on this, we constructed the mutant strain T. aotearoense SCUT27/ Δldh / ΔpflA , which not only possesses higher ethanol tolerance and production but also has enhanced ethanol/acetate ratio that is important for economical ethanol production. Compared to T. aotearoense SCUT27/ Δldh , the mutant strain could resist to 5% (v/v) exogenous ethanol and produce 49 % more ethanol (38.82 g/L vs. 26.05 g/L) in 5-L bioreactor. In addition, the final concentration of ethanol reached 45.01 g/L by immobilized cell fermentation, which is the highest value obtained in T. aotearoense SCUT27. Simultaneously, the ethanol/acetate ratio of the mutant strain achieved 6.82, which was 2.16-fold higher than that of the parental strain. [ABSTRACT FROM AUTHOR]

Metal ions in fermentation media is very crucial for yeast growth and fermentation performance. Other than that, they also have roles for protecting yeast cells against environmental stress factors. In the present study, we investigate the role of calcium ions on fermentation performance and stress tolerance. Most study focus only on one stress factor, while in the present study we tested the effect of calcium ion supplementation against four stress factors, namely ethanol, hyperosmotic, weak acid, and oxidative stresses. The results of the present study indicate that calcium ion has positive role in cell growth and fermentation performance as indicated by significantly higher OD600 nm and higher ethanol produced when calcium ion present in the fermentation media. Calcium ion was also found improving the yeast cell tolerance to all stress factors tested. Therefore, we propose that calcium ion act as general stress protectant for the yeast strain used in this study. [ABSTRACT FROM AUTHOR]

• Integration of a green biorefinery with ethanol fermentation was evaluated. • 90% of the green juice crude protein was recovered in the protein concentrate. • Nanofiltration raised the sugar composition in the brown juice from 2.4 to 13.6 %. • Purification of ethanol from concentrated brown juice used up to 45% less energy. • DWC was the best choice to purify ethanol among the tested extractive distillations. The objective of this study is to propose the integration of a green protein biorefinery with ethanol production and to highlight the potential of nanofiltration membrane technologies and extractive distillation in the separation and purification of valuable substances. Depending on the product and its purity, the nanofiltration membrane can help in decreasing energy expenditure and greenhouse gas emissions while extractive distillation overcomes the water–ethanol azeotrope formation. The aim is to enhance the sustainability of biorefinery processes by integrating new separation techniques and adopting process intensification. The concentration of the residual brown juice using nanofiltration reduced its water content and favored the sugar conversion into ethanol while concomitantly decreasing the formation of byproducts. It has been shown that these configurations (with the presence of nanofiltration and intensified) have lower energy consumption compared to the proposed classical sequence. The results of the simulations indicate that better results are obtained with the extractive distillation using a dividing-wall column, achieving around a 50 % reduction in energy consumption and a 58 % reduction in CO 2 emissions. [ABSTRACT FROM AUTHOR]

This paper aimed to use the major part of carbohydrate fractions in enzymatic hydrolysate of sweet sorghum bagasse, acetone-butanol-ethanol (ABE) fermentation was performed following the ethanol fermentation of hexoses. In batch ethanol fermentation stage, 50.8 ± 3.2 g/L of ethanol was produced from 111.5 g/L of glucose in hydrolysate. After ethanol recovery by batch vacuum distillation, 123.6 ± 15.6 g/L of ethanol was obtained in the distillate, while 47.2 ± 2.5 g/L of xylose was remained in the fermentation broth. The ethanol-free broth was further used as the substrate for ABE fermentation. Compared with yeast remaining scenario, the cell-free ethanol fermentation broth showed a better performance in ABE production. 7.37 ± 0.33 g/L of butanol and 10.93 ± 0.54 g/L of ABE solvent were produced after 120 h of batch fermentation. Based on the biorefinery strategy that cascade two-types of fermentation process, the overall solvents yield boosted significantly, about 144.8 g of ethanol, 17.3 g of butanol and 4.8 g of acetone can be produced from 1 kg sweet sorghum bagasse. • High concentration of sugar was obtained by fed-batch enzymatic hydrolysis of the pretreated pulp. • Ethanol was recovered by vacuum distillation after batch fermentation of enzymatic hydrolysate. • The ethanol removal broth was used as the substrate of ABE fermentation. • About 144.8 g of ethanol, 17.3 g of butanol and 4.8 g of acetone per 1 kg of raw material was achieved. [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]

Background: Ethanol concentration (PE), ethanol productivity (QP) and sugar consumption (SC) are important values in industrial ethanol production. In this study, initial sugar and nitrogen (urea) concentrations in sweet sorghum stem juice (SSJ) were optimized for high PE (=10%, v/v), QP, (=2.5 g/L·h) and SC (=90%) by Saccharomyces cerevisiae SSJKKU01. Then, repeated-batch fermentations under normal gravity (NG) and high gravity (HG) conditions were studied. Results: The initial sugar at 208 g/L and urea at 2.75 g/Lwere the optimumvalues tomeet the criteria. At the initial yeast cell concentration of ~1 × 108 cells/mL, the PE, QP and SCwere 97.06 g/L, 3.24 g/L·h and 95.43%, respectively. Repeated-batch fermentations showed that the ethanol production efficiency of eight successive cycleswith and without aeration were not significantly different when the initial sugar of cycles 2 to 8 was under NG conditions (~140 g/L). Positive effects of aeration were observed when the initial sugar from cycle 2 was under HG conditions (180-200 g/L). The PE and QP under no aeration were consecutively lower from cycle 1 to cycle 6. Additionally, aeration affected ergosterol formation in yeast cell membrane at high ethanol concentrations, whereas trehalose content under all conditions was not different. Conclusion: Initial sugar, sufficient nitrogen and appropriated aeration are necessary for promoting yeast growth and ethanol fermentation. The SSJ was successfully used as an ethanol production medium for a high level of ethanol production. Aeration was not essential for repeated-batch fermentation under NG conditions, but it was beneficial under HG conditions. [ABSTRACT FROM AUTHOR]

The budding yeast Saccharomyces cerevisiae remains a central position among biofuel-producing organisms. However, the gene expression regulatory networks behind the ethanol fermentation is still not fully understood. Using a static fermentation model, we have examined the ethanol yields on biomass of deletion mutants for all yeast nonessential genes encoding transcription factors and their related proteins in the yeast genome. A total of 20 (about 10%) transcription factors are identified to be regulators of ethanol production during fermentation. These transcription factors are mainly involved in cell cycling, chromatin remodeling, transcription, stress response, protein synthesis and lipid synthesis. Our data provides a basis for further understanding mechanisms regulating ethanol production in budding yeast. • A genetic screen identified 18 transcription factors involved in ethanol production. • Chromosomal remodeling factors mainly affect ethanol production negatively. • Deletion of INO2 , INO4 or HAC1 reduces ethanol production. • Deletion of RSC1 increases ethanol tolerance of yeast cells. [ABSTRACT FROM AUTHOR]

Trehalase catalyzes the hydrolysis of the non-reducing disaccharide trehalose. The highly active trehalase MthT from Myceliophthora thermophila was screened from the trehalase genes of six species of filamentous fungi. An ingenious multi-copy knock-in expression strategy mediated by the CRISPR/Cas9 tool and medium optimization were used to improve MthT production in Aspergillus niger, up to 1698.83 U/mL. The protein background was dramatically abated due to insertion. The recombinant MthT showed optimal activity at pH 5.5 and 60 °C, and exhibited prominent thermal stability between 50 and 60 °C under acid conditions (pH 4.5–6.5). The ethanol conversion rate (ethanol yield/total glucose) was significantly improved by addition of MthT (51.88%) compared with MthT absence (34.38%), using 30% starch saccharification liquid. The results of this study provided an effective strategy, established a convenient platform for heterologous expression in A. niger and showed a potential strategy to decrease production costs in industrial ethanol production. [ABSTRACT FROM AUTHOR]

Herbicides inhibiting either aromatic or branched-chain amino acid biosynthesis trigger similar physiological responses in plants, despite their different mechanism of action. Both types of herbicides are known to activate ethanol fermentation by inducing the expression of fermentative genes; however, the mechanism of such transcriptional regulation has not been investigated so far. In plants exposed to low-oxygen conditions, ethanol fermentation is transcriptionally controlled by the ethylene response factors-VII (ERF-VIIs), whose stability is controlled in an oxygen-dependent manner by the Cys-Arg branch of the N-degron pathway. In this study, we investigated the role of ERF-VIIs in the regulation of the ethanol fermentation pathway in herbicide-treated Arabidopsis plants grown under aerobic conditions. Our results demonstrate that these transcriptional regulators are stabilized in response to herbicide treatment and are required for ethanol fermentation in these conditions. We also observed that mutants with reduced fermentative potential exhibit higher sensitivity to herbicide treatments, thus revealing the existence of a mechanism that mimics oxygen deprivation to activate metabolic pathways that enhance herbicide tolerance. We speculate that this signaling pathway may represent a potential target in agriculture to affect tolerance to herbicides that inhibit amino acid biosynthesis. [ABSTRACT FROM AUTHOR]

• Humic substances (HS) consisted mainly of polyphenols and polysaccharides. • HS derived from rice straw promoted tomato growth. • HS exhibited an inhibitory effect on saccharification and fermentation. • HS production integrated with ethanol fermentation is a strategy for straw utilization. The aim of this study was to investigate the effects of bioactives derived from rice straw on tomato growth and develop an integrated process for utilization of straw. The humic substances (HS) was obtained from rice straw in this study. To investigate the effect of HS on tomato growth, tomato seedlings were sprayed with HS and the changes in morphology were measured. Compared with the control, the relative stem heights and leaf numbers of the tomato plants increased by 17.05% and 23.47% for polyphenols in HS and by 28.27% and 17.66% for polysaccharides in HS, respectively. Moreover, the inhibition of HS on cellulase activity and ethanol fermentation were confirmed in this study. When HS was added, the activities of FPase, CMCase and β-glucosidase decreased by 37.29%, 11.54% and 30.70%, respectively. Essentially, the production of HS could be considered as a removal step prior to the bioconversion of the straw into ethanol, and it increased the productivity of ethanol fermentation by 29.39%. The findings demonstrated that HS from rice straw could be successfully used as an environmentally friendly product to increase plant yield and, the residue after HS removal exhibited an improved efficiency of bioconversion to ethanol, making biofuels more attractive. [ABSTRACT FROM AUTHOR]

This study reports on the evaluation of a two-stage pretreatment process for preparing cotton gin trash (CGT) for conversation to ethanol. During the first stage, CGT was mixed with acid at 12% H2SO4 on solids and heated to 180 °C for 15 min in a pressurised stirred reactor. Pressed first-stage pretreated fibres were heated to 200 °C for 5 min during the second stage. The two-stage process facilitated excellent sugar recovery from both cellulose (84%) and hemicellulose (78%) fractions of CGT. Recombinant yeast GSF335 propagated on first-stage liquors yielded 41.8 g kg−1 of dry CGT and was compared with the commercial yeast during separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentations (SSF). SHF of pretreated CGT fibre yielded the equivalent of 66.2 and 64.0 kg ethanol per tonne of unprocessed CGT with GSF335 and the commercial yeast, respectively. SSF ethanol yields for the commercial yeast were significantly lower (50.3 kg) while GSF335 correspondingly produced 63.8 kg ethanol per tonne of raw CGT. [ABSTRACT FROM AUTHOR]

Maize starch was irradiated by a Co60 irradiator with different doses. The morphology and physicochemical properties of native and irradiated starches were investigated. Scanning electron microscopy showed that the shape and size of starch granules did not change after irradiation. However, the irradiated starch granules were easily destroyed by dissolution. Irradiation also caused the change of starch color, the decrease in the pH value, light transmittance, stability index, degree of polymerization, total sugar content, and the increase in the swelling index and the reducing sugar content. In this study, irradiated maize starch was also used as material for ethanol fermentation to investigate its potential as a pretreatment method. Results showed that the ethanol yield of cooked and raw starch fermentation using irradiated starch increased by 20.41 % and 5.18 %, respectively, and the ethanol concentration increased by 3 % and 2 %. This finding indicated that irradiation effectively improved the utilization rate of maize starch, making it an effective pretreatment method for ethanol fermentation. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Controlling extracellular redox potential enhances the tolerance of yeast to furfural. • Intracellular redox status shows a tight correlation with extracellular redox potential. • −100 mV is an optimal redox level to obtain high biomass and ethanol titer. Abstract Furfural is a major toxic byproduct present in the hydrolysate of lignocellulosic biomass, which inhibits the growth and ethanol fermentation of Saccharomyces cerevisiae. To enhance yeast tolerance to furfural, extracellular redox potential (ORP) regulation was employed for the fermentation system through controlling ORP at −150 mV, −100 mV and −50 mV, respectively, by adjusting its aeration. When ORP was controlled at −100 mV, yeast cells exhibited improved growth, furfural degradation and ethanol production. Analysis of intracellular redox pairs such as NADH/NAD+ and GSH/GSSG indicated a correlation between extracellular ORP and intracellular redox homeostasis. Moreover, intracellular reactive oxygen species (ROS) caused by furfural stress decreased under the redox control condition, which consequently conferred yeast cells tolerance to furfural. Comparative transcriptome analysis for yeast cells sampling under the ORP control at −100 mV further revealed that the expression of genes for proliferation was up-regulated to degrade furfural more efficiently. These results demonstrated that extracellular ORP regulation would be a strategy for enhancing yeast tolerance to furfural stress during cellulosic ethanol fermentation. [ABSTRACT FROM AUTHOR]

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 • Ratio of α-amylase to glucoamylase is important in saccharifying cassava pulp (CP). • Cold hydrolysis at 50 °C followed by 30 °C is effective in CP saccharification. • A model was developed for predicting the performance of cold hydrolysis process. • A sequential process for bioconversion of CP to ethanol was proposed. • The proposed process yielded 27.4 g-ethanol/L, with 57.8% fermentation efficiency. Abstract The present study investigated cold hydrolysis of cassava pulp (CP) and the use of cold hydrolysis with simultaneous saccharification and fermentation (SSF) for ethanol production. Cold hydrolysis of 100 g-CP/L at 50 °C for 2 h, followed by at 30 °C for 72 h resulted in the production of 71.5 ± 1.8 g/L of reducing sugar, with a yield of 0.72 g/g-CP. A mathematical model describing the cold hydrolysis process was subsequently developed. The model proved to be applicable for other cold hydrolysis systems with satisfactory results. The sequential process of cold hydrolysis at 50 °C for 2 h, followed by SSF at 30 °C for 72 h gave 27.4 g-ethanol/L, with a productivity of 0.37 g/(L h) and a fermentation efficiency of 57.58%. Based on the results, a bioconversion process for CP to ethanol was proposed. In this process, 1 kg of ethanol could be produced from 3.65 kg of CP without any nutrient supplementation. [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]

Highlights • A continuous fermentation process with a delayed product inhibition is considered. • Stability analysis of the control system with PI algorithm and process delay is given. • The negative effect of measurement noises is considered. • The process is stabilized for any delay and for a sufficiently high controller gain. • Filtering of the process variable reduces the effect of noises, but affects stability. Abstract The paper addresses the problem of stabilization of ethanol concentration in continuous fermentation processes. The stability analysis is performed for a class of continuous fermentation processes assuming that the possible oscillatory behavior results from a delayed response of microorganisms to inhibitory effects of ethanol concentration and that the specific growth rate is a monotonic function of substrate and a monotonic function of product concentrations. Treating dilution rate as the manipulated variable, it is shown that the classical PI controller is able to stabilize the oscillating process in the whole range of operating regions. Moreover, for a sufficiently large controller gain, the closed-loop system is asymptotically stable for any process delay. However, a high-gain controller may lead to extensive control signal activity and wear of actuator in the presence of measurement noises. To reduce the negative effect of measurement noises, the measured process variable is filtered by using the first order filter. Then, it is shown that the closed-loop system with the filter can also be stabilized for any process delay. The simulation results confirmed the effectiveness of the proposed closed-loop strategy with and without filtering. [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]

[Display omitted] • Raman spectroscopy and chemometrics track metabolic changes in individual yeast cells. • Yeast cells exhibit 3 stages during high gravity ethanol fermentation. • Unique protein structure and increased triacylglycerol synthesis as a defense from ethanol stress. Saccharomyces cerevisiae is the most common microbe used for the industrial production of bioethanol, and it encounters various stresses that inhibit cell growth and metabolism during fermentation. However, little is currently known about the physiological changes that occur in individual yeast cells during ethanol fermentation. Therefore, in this work, Raman spectroscopy and chemometric techniques were employed to monitor the metabolic changes of individual yeast cells at distinct stages during high gravity ethanol fermentation. Raman tweezers was used to acquire the Raman spectra of individual yeast cells. Multivariate curve resolution-alternating least squares (MCR-ALS) and principal component analysis were employed to analyze the Raman spectra dataset. MCR-ALS extracted the spectra of proteins, phospholipids, and triacylglycerols and their relative contents in individual cells. Changes in intracellular biomolecules showed that yeast cells undergo three distinct physiological stages during fermentation. In addition, heterogeneity among yeast cells significantly increased in the late fermentation period, and different yeast cells may respond to ethanol stress via different mechanisms. Our findings suggest that the combination of Raman tweezers and chemometrics approaches allows for characterizing the dynamics of molecular components within individual cells. This approach can serve as a valuable tool in investigating the resistance mechanism and metabolic heterogeneity of yeast cells during ethanol fermentation. [ABSTRACT FROM AUTHOR]

In the present investigation, an collagen fibre (CF), abundant natural biomass, was successfully grafted by polyethyleneimine (PEI). The resultant PEI grafted collagen fibre (CF-PEI) was employed as biocompatible and high cell loading support matrix for the immobilization of Saccharomyces cerevisiae cells. The as-prepared CF-PEI immobilized cells (CF-PEI-cell) exhibited high activity and stability for both batch and continuous fermentation. In batch fermentation, CF-PEI-cells showed enhanced stability as compared with other matrices supported cells, and produced an average ethanol concentration of 45.04 g/L with ethanol yield (YP/S) of 0.46 g/g and glucose conversion efficiency (η) of 90.4%. Continuous fermentation was operated stably in a down-flow trickling bed reactor charged with CF-PEI-cell for a total of 2 months. When the dilution rate was 0.16 1/h, the average ethanol productivity reached 7.18 g/(L h) with η of 88.94%. Further scanning electron microscopy observations confirmed that yeast cells can proliferate on the surface of CF-PEI during ethanol fermentation, which demonstrates that CF-PEI is indeed an ideal matrix for the immobilization of yeast cells. [ABSTRACT FROM AUTHOR]

Garcinia cambogia, a Chinese herbal medicine, was popular due to its effect for weight loss. The main medical component inside was determined to be hydroxycitric acid (HCA). To realize the resource technology of garcinia cambogia residue, Optimum ethanol production from residues was investigated, and the effects of remaining HCA on the ethanol yield were investigated. A Plackett-Burman experimental design was used to screen the significance of several influencing factors, and cellulase, yeast extract, and KH2PO4 were observed to exert important effects. The optimum ethanol fermentation conditions were determined through an orthogonal design to include a cellulase concentration of 100 U/g, a yeast extract concentration of 15 g/L, and a KH2PO4 concentration of 1.0 g/L. The ethanol concentration obtained under optimal conditions was 4.0 g/L. The remained HCA in the residues showed minimal influences on ethanol fermentation and could even increase ethanol yield at low concentrations. [ABSTRACT FROM AUTHOR]

In this study, it was found that the type of phenolic acids derived from rice straw was the major factor affecting ethanol fermentation by Pichia stipitis . The aim of this study was to investigate the inhibitory effect of phenolic acids on ethanol fermentation with rice straw. Different cellulases produced different ratios of free phenolic acids to soluble conjugated phenolic acids, resulting in different fermentation efficiencies. Free phenolic acids exhibited much higher inhibitory effect than conjugated phenolic acids. The flow cytometry results indicated that the damage to cell membranes was the primary mechanism of inhibition of ethanol fermentation by phenolic acids. The removal of free phenolic acids from the hydrolysates increased ethanol productivity by 2.0-fold, indicating that the free phenolic acids would be the major inhibitors formed during saccharification. The integrated process for ethanol and phenolic acids may constitute a new strategy for the production of low-cost ethanol. [ABSTRACT FROM AUTHOR]

Miscanthus × giganteus is a perennial rhizomatous grass which is used as a biofuel crop. Due to its high yields, low production costs, resistance to low temperatures, low soil requirements and, above all, high cellulose content, miscanthus can be a useful resource for ethanol production. The aim of this study was to determine the effect of two fertilization regimes (sewage sludge/mineral NPK) during miscanthus cultivation on the chemical composition of biomass, the content of major lignocellulosic factions and the effectiveness of miscanthus conversion to bioethanol. The results indicate that fertilization treatments influenced biomass yield and the content of major lignocellulosic fractions. Bioethanol production was higher when hydrolysis and fermentation processes were conducted separately than when saccharification and fermentation were conducted simultaneously. Ethanol production increased by 30% and 40% in response to sewage sludge and NPK (equivalent nitrogen content = 160 kg N/ha) fertilization, respectively, in comparison with unfertilized crops. [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]

In this study, dilute alkali salts (0.6% NaClO, 0.067% Na 2 S) pretreatment at 10% sulfidity under the autoclave system at 120 °C for 40 min was used for pretreating bamboo shoot shell (BSS). Furthermore, FT-IR, XRD and SEM were employed to characterize the changes in the cellulose structural characteristics (porosity, morphology, and crystallinity) of the pretreated BSS solid residue. After 72 h, the reducing sugars and glucose from the enzymatic in situ hydrolysis of 50 g/L pretreated BSS in dilute NaClO/Na 2 S media could be obtained at 31.11 and 20.32 g/L, respectively. Finally, the obtained BSS-hydrolysates containing alkalic salt NaClO/Na 2 S resulted in slightly negative effects on the ethanol production. Glucose in BSS-hydrolysates was fermented from 20.0 to 0.17 g/L within 48 h, and an ethanol yield of 0.41 g/g glucose, which represents 80.1% of the theoretical yield, was obtained. This study provided an effective strategy for potential utilization of BSS. [ABSTRACT FROM AUTHOR]

[Display omitted] • Rice husk improves yeast tolerance to high temperature and ethanol concentration. • Yeast biofilms on rice husks tolerate high temperature and ethanol concentration. • Kinetic models illustrate the promotion of fermentation by rice husk. • A mixed substrate was applied in the ethanol fermentation. In recent years, growing attention has been devoted to improving stress resistance of yeast to temperature and ethanol concentration as it affects fermentation productivity in biofuel ethanol industry. Rice husk was found to increase the resistance of yeast to high temperature and high ethanol concentration, which can be attributed to yeast cell adsorption on rice husk. Compared with no addition of rice husk, the ethanol yield of brown rice fermented at 32 °C and 39 °C with 1.0 % rice husk increased by 9.4 % and 5.1 %. The fermentation kinetics of cell growth and ethanol formation could be described by the improved Logistic model and Luedeking-Piret model, respectively. Based on the effect of rice husk, the higher ethanol concentration (106.7 g/L at 32 °C) and complete substrate utilization could be achieved by using a mixed substrate at dry mass ratio of whole rice to brown rice of 3:1. [ABSTRACT FROM AUTHOR]

In this study, soluble polysaccharides (SPs) were used to prepare the complexes with different degrees of polymerization and ratios of saccharide to phenolic acids (PAs) and their effects on yeast growth and ethanol fermentation were studied. Time-of-flight mass spectrometry showed that the lower the degree of saccharide polymerization, the higher the PA content. Oligosaccharide-PAs played an important role in ethanol fermentation. ATP/ADP and flow cytometry indicated that oligosaccharide-PAs could improve cell viability and increase the proportion of living and dead cells. Atomic force microscopy and confocal laser scanning microscopy images showed that the oligosaccharide-PAs induced the formation of extracellular matrixes, maintained the cellular biomorphology. The oligosaccharide-PAs also regulated NAD+/NADH, NAPD+/NADPH, and reduced the intracellular peroxide content. Thus, the oligosaccharide-PAs improved the cell viability by reducing the intracellular peroxide content and maintaining the cellular biomorphology. [Display omitted] • Saccharide polymerization has a strong correlation with the ratio of saccharide to PAs. • Oligosaccharides-PAs complex had a stronger effect than SPs on ethanol fermentation. • The complex can reduce intracellular peroxide content and maintain cell morphology. [ABSTRACT FROM AUTHOR]

[Display omitted] • Whole-cell biomass utilization was completed with newly integrated biorefinery. • Hydrolysis yielded 89 % of total carbohydrate within 4 min using optimized process. • Volume reduction decreased solvent usage by 75 % and recovered all oil within 20 min. • Bioethanol yield of sole hydrolysate was comparable with conventional YPD medium. • Newly developed process decreased OPEX and CAPEX by 82.7 % and 70.1 %, respectively. Microalgae are a promising source of biomass for the production of biofuels, but their use is currently infeasible because of changes in the biofuel market and the lack of an optimized refinery process. The biomass of oleaginous microalgae consists of up to 50% lipids and 50% carbohydrates and proteins, so the biorefinery process must be able to use whole cell biomass. In this work, an alternative process to the standard biorefinery approach of lipid extraction and treatment of lipid-extracted residue was developed and tested using oleaginous Chlorella sp. ABC-001. First, a hydrolysis process was optimized to achieve cell lysis. At 170 °C and 0.1 N H 2 SO 4 , 89.0% of total carbohydrates were hydrolyzed to monosaccharides within 4 min. Then, a volume reduction process (brief and mild centrifugation) was applied to reduce the extraction time and the use of organic solvent. By reducing the aqueous phase from the hydrolysate, all lipids were extracted by vortexing with just a quarter of the original volume (10 mL) within 20 min. Finally, after extraction the aqueous phase was utilized as the sole growth medium for ethanol production by Saccharomyces cerevisiae KL17. The resulting ethanol yield was 0.39 g ethanol/g sugar, comparable to that achieved using conventional yeast-peptone-dextrose (YPD) medium (0.41 g ethanol/g sugar). Furthermore, relative to the conventional process, techno-economic analysis confirmed that the newly developed process decreased operational expenditures by 82.7% and decreased capital expenditures by 70.1%. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Since both ethanol and butanol fermentations are urgently developed processes with the biofuel-demand increasing, performance comparison of aerobic ethanol fermentation and anerobic butanol fermentation in a continuous and closed-circulating fermentation (CCCF) system was necessary to achieve their fermentation characteristics and further optimize the fermentation process. Fermentation and pervaporation parameters including the average cell concentration, glucose consumption rate, cumulated production concentration, product flux, and separation factor of ethanol fermentation were 11.45 g/L, 3.70 g/L/h, 655.83 g/L, 378.5 g/m2/h, and 4.83, respectively, the corresponding parameters of butanol fermentation were 2.19 g/L, 0.61 g/L/h, 28.03 g/L, 58.56 g/m2/h, and 10.62, respectively. Profiles of fermentation and pervaporation parameters indicated that the intensity and efficiency of ethanol fermentation was higher than butanol fermentation, but the stability of butanol fermentation was superior to ethanol fermentation. Although the two fermentation processes had different features, the performance indicated the application prospect of both ethanol and butanol production by the CCCF system. [ABSTRACT FROM PUBLISHER]

Methane and ethanol were co-produced from different feedstock, including a mixture of dairy manure and soybean straw (DMS), a mixture of pig manure and soybean straw (PMS), and soybean straw alone (SS), after anaerobic digestion times of 30 and 60 days in mesophilic conditions. Digesting DMS for 60 days led to the highest methane yield of 115.3 g/kg dry raw feed; however, the lowest ethanol yield of 88 g/kg dry raw feed was observed. After 30 days, SS yielded the lowest methane levels (45.2 g/kg dry raw feed) but the highest ethanol levels (113.5 g/kg dry raw feed). Analysis of the net energy balance showed that the highest net energy balance, 6549 kJ/kg of dry raw feedstock, was achieved from the digestion of DMS for 60 days. Overall, both the type of feedstock and length of digestion time played important roles in the integrated processing of methane and ethanol from livestock manure and straw. [ABSTRACT FROM AUTHOR]

One of the key processes in making beer is fermentation. In the fermentation process, brewer's yeast plays an essential role in both the production of ethanol and the flavor profile of beer. Therefore, the mechanism of ethanol fermentation by of brewer's yeast is attracting much attention. The high ethanol productivity of sake yeast has provided a good basis from which to investigate the factors that regulate the fermentation rates of brewer's yeast. Recent studies found that the elevated fermentation rate of sake Saccharomyces cerevisiae species is closely related to a defective transition from vegetative growth to the quiescent (G 0 ) state. In the present study, to clarify the relationship between the fermentation rate of brewer's yeast and entry into G 0 , we constructed two types of mutant of the bottom-fermenting brewer's yeast Saccharomyces pastorianus Weihenstephan 34/70: a RIM15 gene disruptant that was defective in entry into G 0 ; and a CLN3 Δ PEST mutant, in which the G 1 cyclin Cln3p accumulated at high levels. Both strains exhibited higher fermentation rates under high-maltose medium or high-gravity wort conditions (20° Plato) as compared with the wild-type strain. Furthermore, G 1 arrest and/or G 0 entry were defective in both the RIM15 disruptant and the CLN3 Δ PEST mutant as compared with the wild-type strain. Taken together, these results indicate that regulation of the G 0 /G 1 transition might govern the fermentation rate of bottom-fermenting brewer's yeast in high-gravity wort. [ABSTRACT FROM AUTHOR]

In this study, a Saccharomyces cerevisiae recombinant strain 14 was constructed through genome shuffling method by transferring the whole genomic DNA of Candida intermedia strain 23 into a thermo-tolerant S. cerevisiae strain. The recombinant strain 14 combined the good natures of both parent strains that efficiently produced ethanol from glucose and single cell protein from xylose with 54.6% crude protein and all essential amino acids except cysteine at 35 °C. Importantly, the recombinant strain 14 produced 64.07 g/L ethanol from 25% (w/v) NaOH-pretreated and washed corn stover with the ethanol yield of 0.26 g/g total stover by fed-batch simultaneous saccharification and fermentation and produced 66.50 g/L dry cell mass subsequently from the residual hydrolysate and ethanol. Therefore, this study represents a feasible method to comprehensively utilize hexose and pentose in lignocellulosic materials. [ABSTRACT FROM AUTHOR]

Stillage reflux fermentation in food waste ethanol fermentation could reduce sewage discharge but exert a harmful effect because of side-product accumulation. In this study, regulation methods based on metabolic regulation and side-product alleviation were conducted. Result demonstrated that controlling the proper oxidation–reduction potential value (−150 mV to −250 mV) could reduce the harmful effect, improve ethanol yield by 21%, and reduce fermentation time by 20%. The methods of adding calcium carbonate to adjust the accumulated lactic acid showed that ethanol yield increased by 17.3%, and fermentation time decreased by 20%. The accumulated glyceal also shows that these two methods can reduce the harmful effect. Fermentation time lasted for seven times without effect, and metabolic regulation had a better effect than side-product regulation. [ABSTRACT FROM AUTHOR]

Bioethanol is a renewable biofuel that has a strong inhibitory effect on cells in bioethanol fermentation by yeast. In this study, carbon nanotube (CNT)-mixed polydimethylsiloxane (PDMS) membranes were used for ethanol recovery from model solutions as well as for fermentation by self-flocculating yeast. Imbedding CNTs into the PDMS membrane led to enhanced ethanol recovery, with a maximum total flux of 128.7 g/m 2 h and an ethanol titer of 615.1 g/L in permeate. The CNTs can provide a flexible route for ethanol transport through the inner tubes or along the smooth surface. In fed-batch fermentation incorporating pervaporation, 112.3 g/L of ethanol was produced with an overall ethanol productivity and yield of 2.23 g/L h and 0.45 g/g, respectively. The membrane produced a highly concentrated condensate containing 400.3–487.5 g/L of ethanol. Furthermore, as yeast flocs can be throttled down in the bioreactor, self-flocculating yeast can be used to prevent membrane fouling induced by cell adsorption on the membrane. Therefore, the CNT-mixed membrane coupled with ethanol fermentation by self-flocculating yeast not only reduces ethanol-mediated inhibition of cells but also saves the production cost because of the reduced fouling risk. Thus, this combination approach has potential in industrial bioethanol production for long-time operation. [ABSTRACT FROM AUTHOR]

In this paper, genetic algorithm was used to investigate mathematical modeling of ethanol fermentation in a continuous conventional bioreactor (CCBR) and a continuous membrane bioreactor (CMBR) by ethanol permselective polydimethylsiloxane (PDMS) membrane. A lab scale CMBR with medium glucose concentration of 100 g L −1 and Saccharomyces cerevisiae microorganism was designed and fabricated. At dilution rate of 0.14 h −1 , maximum specific cell growth rate and productivity of 0.27 h −1 and 6.49 g L −1 h −1 were respectively found in CMBR. However, at very high dilution rate, the performance of CMBR was quite similar to conventional fermentation on account of insufficient incubation time. In both systems, genetic algorithm modeling of cell growth, ethanol production and glucose concentration were conducted based on Monod and Moser kinetic models during each retention time at unsteady condition. The results showed that Moser kinetic model was more satisfactory and desirable than Monod model. [ABSTRACT FROM AUTHOR]

Raw materials and pollution control are key issues for the ethanol fermentation industry. To address these concerns, food waste was selected as fermentation substrate, and stillage reflux was carried out in this study. Reflux was used seven times during fermentation. Corresponding ethanol and reducing sugar were detected. Accumulation of by-products, such as organic acid, sodium chloride, and glycerol, was investigated. Lactic acid was observed to accumulate up to 120 g/L, and sodium chloride reached 0.14 mol/L. Other by-products did not accumulate. The first five cycles of reflux increased ethanol concentration, which prolonged fermentation time. Further increases in reflux time negatively influenced ethanol fermentation. Single-factor analysis with lactic acid and sodium chloride demonstrated that both factors affected ethanol fermentation, but lactic acid induced more effects. [ABSTRACT FROM AUTHOR]

Saccharomyces cerevisiae is the most widely used fermentation organism for ethanol production. However, the gene expression regulatory networks behind the ethanol fermentation are still not fully understood. Using a static fermentation model, we examined the ethanol yields on biomass of deletion mutants for 77 yeast genes encoding nonessential transcription factors, and found that deletion mutants for ACE2 and SWI5 showed dramatically increased ethanol yields. Overexpression of ACE2 or SWI5 in wild type cells reduced their ethanol yields. Furthermore, among the 34 target genes regulated by Ace2 and Swi5, deletion of CTS1, RPS4a, SIC1, EGT2, DSE2, or SCP160 led to increased ethanol yields, with the former two showing higher effects. Overexpression of CTS1 or RPS4a in both ace2/ace2 and swi5/swi5 mutants reduced their ethanol yields. In contrast, deletion of MCR1 or HO significantly decreased ethanol yields, with the former one showing the highest effect. Therefore, Ace2 and Swi5 are two negative regulators of ethanol yield during static fermentation of yeast cells, and both CTS1 and RPS4a are major effectors mediating these two transcription factors in regulating ethanol production. [ABSTRACT FROM AUTHOR]

Pretreatment with ozone combined with aqueous ammonia was used to recover residual organic carbon from recalcitrant solid digestate for ethanol production after anaerobic digestion (AD) of rice straw. Methane yield of AD at mesophilic and thermophilic conditions, and ethanol production of solid digestate were investigated. The results showed that the methane yield at thermophilic temperature was 72.2% higher than that at mesophilic temperature under the same conditions of 24 days and 17% solid concentration. And also the ethanol production efficiency of solid digestate after thermophilic process was 24.3% higher than that of solid digestate after mesophilic process. In this study, the optimal conditions for integrated methane and ethanol processes were determined as 55 °C, 17% solid concentration and 24 days. 58.6% of glucose conversion, 142.8 g/kg of methane yield and 65.2 g/kg of ethanol yield were achieved, and the highest net energy balance was calculated as 6416 kJ/kg. [ABSTRACT FROM AUTHOR]