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Waterlogging stress is one of the major abiotic stresses affecting the productivity and quality of many crops worldwide. However, the mechanisms of waterlogging tolerance are still elusive in barley. In this study, we identify key differentially expressed genes (DEGs) and differential metabolites (DM) that mediate distinct waterlogging tolerance strategies in leaf and root of two barley varieties with contrasting waterlogging tolerance under different waterlogging treatments. Transcriptome profiling revealed that the response of roots was more distinct than that of leaves in both varieties, in which the number of downregulated genes in roots was 7.41-fold higher than that in leaves of waterlogging sensitive variety after 72 h of waterlogging stress. We also found the number of waterlogging stress-induced upregulated DEGs in the waterlogging tolerant variety was higher than that of the waterlogging sensitive variety in both leaves and roots in 1 h and 72 h treatment. This suggested the waterlogging tolerant variety may respond more quickly to waterlogging stress. Meanwhile, phenylpropanoid biosynthesis pathway was identified to play critical roles in waterlogging tolerant variety by improving cell wall biogenesis and peroxidase activity through DEGs such as Peroxidase (PERs) and Cinnamoyl-CoA reductases (CCRs) to improve resistance to waterlogging. Based on metabolomic and transcriptomic analysis, we found the waterlogging tolerant variety can better alleviate the energy deficiency via higher sugar content, reduced lactate accumulation, and improved ethanol fermentation activity compared to the waterlogging sensitive variety. In summary, our results provide waterlogging tolerance strategies in barley to guide the development of elite genetic resources towards waterlogging-tolerant crop varieties. [ABSTRACT FROM AUTHOR]

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]

Simple Summary: Pyruvate decarboxylase (PDC) is a key enzyme involved in ethanol fermentation, a process for the production of biofuels. Thermostable and oxygen-stable PDC activity is highly desirable for biotechnological applications at high temperatures. The enzymes from the thermoacidophiles Saccharolobus (formerly Sulfolobus) solfataricus (Ss, Topt = 80 °C) and Sulfolobus acidocaldarius (Sa, Topt = 80 °C) were purified and characterized, and their biophysical and biochemical properties were determined comparatively. The purified enzymes were CoA-dependent and thermostable. There was no loss of activity in the presence of oxygen. In conclusion, both thermostable SsPDC and SaPDC catalyze the CoA-dependent production of acetaldehyde from pyruvate in the presence of oxygen. Pyruvate decarboxylase (PDC) is a key enzyme involved in ethanol fermentation, and it catalyzes the decarboxylation of pyruvate to acetaldehyde and CO2. Bifunctional PORs/PDCs that also have additional pyruvate:ferredoxin oxidoreductase (POR) activity are found in hyperthermophiles, and they are mostly oxygen-sensitive and CoA-dependent. Thermostable and oxygen-stable PDC activity is highly desirable for biotechnological applications. The enzymes from the thermoacidophiles Saccharolobus (formerly Sulfolobus) solfataricus (Ss, Topt = 80 °C) and Sulfolobus acidocaldarius (Sa, Topt = 80 °C) were purified and characterized, and their biophysical and biochemical properties were determined comparatively. Both enzymes were shown to be heterodimeric, and their two subunits were determined by SDS-PAGE to be 37 ± 3 kDa and 65 ± 2 kDa, respectively. The purified enzymes from S. solfataricus and S. acidocaldarius showed both PDC and POR activities which were CoA-dependent, and they were thermostable with half-life times of 2.9 ± 1 and 1.1 ± 1 h at 80 °C, respectively. There was no loss of activity in the presence of oxygen. Optimal pH values for their PDC and POR activity were determined to be 7.9 and 8.6, respectively. In conclusion, both thermostable SsPOR/PDC and SaPOR/PDC catalyze the CoA-dependent production of acetaldehyde from pyruvate in the presence of oxygen. [ABSTRACT FROM AUTHOR]

For many biorefinery processes, the development of effective preservation techniques is essential to avoid any sugar loss between crop-harvesting and fermentation. In this work, five physicochemical techniques (acidification, ozonation, addition of sodium hydrosulfite, sodium sulfate and oil layer) were investigated for the preservation of sugar beet molasses diluted at low (150 g/L) and high (300 g/L) concentration of initial sugars. After 30 days, sugars and metabolites profiles were quantified to determine the optimal preservation technique capable of limiting the biological contamination while preserving as much fermentable sugars as possible. Although none of the strategies was efficient to prevent the microbial contamination at 150 g/L, some approaches allowed preserving more than 90% of fermentable sugars at 300 g/L of initial sugars. Furthermore, the use of 2 g/L of sodium hydrosulfite or acidifying the media to pH 3 allowed the conservation of nearly 100% of the fermentable sugars. Fermentation assays performed after storage indicated that acidification, sodium hydrosulfite and ozonation did not alter the fermentation performances, as the production of ethanol reached 102 g/L after 6 days of incubation. Therefore, the use of sodium hydrosulfite or acidification were considered as relevant strategies for maintaining fermentable sugars in liquid feedstock for bioethanol production. [Display omitted] • Diluted sugar beet molasses was used as feedstock for bioethanol production. • Five storage techniques were tested to preserve fermentable sugars from contamination. • Acidification or addition of Na 2 S 2 O 4 were the most efficient preservation techniques. • 90% of the initial fermentable sugars were preserved after 30 days of storage. • Addition of Na 2 S 2 O 4, acidification and ozonation did not impact the fermentation performances after storage. [ABSTRACT FROM AUTHOR]

Currently, most cotton textile waste is sent to landfill. However, due to the use of synthetic additives and the chemical treatment of cotton fibers, cotton textile waste is difficult to biodegrade. Cotton textile waste can also be subjected to material recycling, or to incineration/gasification to produce energy. Here, we present the optimization of acid hydrolysis of cotton yarn fibers for glucose efficiency. The cotton yarn hydrolysates showed great potential for replacing simple sugar solutions in fermentation media. The highest glucose concentration was obtained in the hydrolysates of cotton yarn hydrolyzed in a 2% solution of sulfuric acid or phosphoric acid at 140–160 °C for 2 h. After 2 h of hydrolysis at 140 °C with 2% H3PO4, the concentration of glucose in the cotton yarn hydrolysate (13.19 g/L) increased fivefold compared with cotton yarn treated under the same conditions with H2SO4 (2.65 g/L). The structural modifications in the solid residues after acid hydrolysis were analyzed using a scanning electron microscope with energy dispersive spectroscopy (SEM-EDS), attenuated total reflectance Fourier-transform infrared spectroscopy (FTIR-ATR), and Raman spectroscopy. The SEM images, IR spectra, and Raman spectra revealed that the most significant changes in the morphology of the fibers occurred when the process was carried out at high temperatures (≥140 °C). Better growth of the yeast strains Saccharomyces cerevisiae Ethanol Red and Saccharomyces cerevisiae Tokay ŁOCK0204 was observed in the medium containing phosphoric acid hydrolysate. The maximum methane yield of 278 dm3/kgVS and the maximum hydrogen yield of 42 dm/kgVS were reported for cotton yarn waste after pretreatment with H3PO4. This might have been linked to the beneficial effect of phosphorus, which is a key nutrient for anaerobic digestion. The proposed hydrolysis method does not generate fermentation inhibitors. [ABSTRACT FROM AUTHOR]

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]

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]

The scarcity of essential minerals in the wort used for bioethanol production has long been a persistent concern in industrial processes. This scarcity can negatively impact various aspects of production, including yeast cell vitality and sugar-to-ethanol conversion. In this study, we assessed the nutritional profile of key components of the industrial bioethanol production process and identified nitrogen, phosphorus, magnesium, manganese, zinc, and copper ions deficiencies. Supplementation of fermentation assays with TMNitrofós was carried out until reaching the maximum allowed for manganese (24.5%), zinc (49.4%), and copper (8.8%). Laboratory-scale fermentation assays were conducted under varying conditions of soluble solids in the wort (20, 24, and 26°Brix). These experiments aimed to assess the primary productivity parameters in response to the application of TMNitrofós. Results showed that fermentations using wort with 24 and 26°Brix supplemented with TMNitrofós led to 7% higher fermentative efficiency compared to the control group. The supplemented fermentations demonstrated higher levels of cellular vitality (76.6%) compared to the control group (55.3%). Considering a scale-up in the bioethanol production process with TMNitrofós supplementation, an increase of 266 m3 of ethanol per month was achieved compared to the control group, resulting in cost savings of R$ 586,879.20.Graphical Abstract: The scarcity of essential minerals in the wort used for bioethanol production has long been a persistent concern in industrial processes. This scarcity can negatively impact various aspects of production, including yeast cell vitality and sugar-to-ethanol conversion. In this study, we assessed the nutritional profile of key components of the industrial bioethanol production process and identified nitrogen, phosphorus, magnesium, manganese, zinc, and copper ions deficiencies. Supplementation of fermentation assays with TMNitrofós was carried out until reaching the maximum allowed for manganese (24.5%), zinc (49.4%), and copper (8.8%). Laboratory-scale fermentation assays were conducted under varying conditions of soluble solids in the wort (20, 24, and 26°Brix). These experiments aimed to assess the primary productivity parameters in response to the application of TMNitrofós. Results showed that fermentations using wort with 24 and 26°Brix supplemented with TMNitrofós led to 7% higher fermentative efficiency compared to the control group. The supplemented fermentations demonstrated higher levels of cellular vitality (76.6%) compared to the control group (55.3%). Considering a scale-up in the bioethanol production process with TMNitrofós supplementation, an increase of 266 m3 of ethanol per month was achieved compared to the control group, resulting in cost savings of R$ 586,879.20. [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]

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]

Background: The industrial production of various alcohols from organic carbon compounds may be performed at high rates and with a low risk of contamination using thermophilic microorganisms as whole-cell catalysts. Thermoanaerobacter species that thrive around 50–75 °C not only perform fermentation of sugars to alcohols, but some also utilize different organic acids as electron acceptors, reducing them to their corresponding alcohols. Results: We purified AdhE as the major NADH- and AdhB as the major NADPH-dependent alcohol dehydrogenase (ADH) from the cell extract of the organic acid-reducing Thermoanaerobacter sp. strain X514. Both enzymes were present in high amounts during growth on glucose with and without isobutyrate, had broad substrate spectra including different aldehydes, with high affinities (< 1 mM) for acetaldehyde and for NADH (AdhE) or NADPH (AdhB). Both enzymes were highly thermostable at the physiological temperature of alcohol production. In addition to AdhE and AdhB, we identified two abundant AdhA-type ADHs based on their genes, which were recombinantly produced and biochemically characterized. The other five ADHs encoded in the genome were only expressed at low levels. Conclusions: According to their biochemical and kinetic properties, AdhE and AdhB are most important for ethanol formation from sugar and reduction of organic acids to alcohols, while the role of the two AdhA-type enzymes is less clear. AdhE is the only abundant aldehyde dehydrogenase for the acetyl-CoA reduction to aldehydes, however, acid reduction may also proceed directly by aldehyde:ferredoxin oxidoreductase. The role of the latter in bio-alcohol formation from sugar and in organic acid reduction needs to be elucidated in future studies. [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]

Long fermentation time and high oxygen partial pressure were significant challenges for high ethanol productivity in solid state fermentation (SSF). In this study, the feasibility of N 2 periodic pulsation to improve ethanol productivity was investigated. Changes of CO 2 concentration and water state distribution in N 2 periodic pulsation SSF were examined. A metabolic flux model was developed to understand the effect of N 2 periodic pulsation on ethanol production. The results indicated that ethanol productivity of 1.75 g/(L·h) in N 2 periodic pulsation group (NPPG) was 34.4% higher than that in control group (CG) within 24 h. The maximum ethanol concentration and yield were 47.52 g/L and 70.80% at 70% moisture content, respectively. The CO 2 concentration in NPPG was well below 5000 ppm at 21 h, which was much lower than 38,080 ppm in CG. Metabolic flux analysis revealed that the metabolic flux towards ethanol increased by 25% with the application of N 2 periodic pulsation. These results confirmed that N 2 periodic pulsation is an effective method for improving ethanol production in solid state fermentation. Image 1 • Ethanol production performance was enhanced by N 2 periodic pulsation. • Ethanol productivity increased by 34.4% with N 2 periodic pulsation. • CO 2 removal and low moisture content could improve ethanol production. • The metabolic flux distribution to ethanol increased by N 2 periodic pulsation. [ABSTRACT FROM AUTHOR]

Diversity of extremophilic microorganisms in mud volcanoes is largely unexplored. Here, we report the isolation of a novel alkaliphilic, mesophilic, fermentative bacterium (strain F-3apT) from a terrestrial mud volcano located at the Taman peninsula, Russia. Cells of strain F-3apT are Gram-stain-positive non-motile rods. The formation of endospores is not observed. The temperature range for growth is 14–42 °C, with an optimum at 37 °C. The pH range for growth is 7.5–11.0, with an optimum at pH 9.0. The isolate utilizes various organic polymeric substances, organic acids, carbohydrates, and proteinaceous compounds. The end products of glucose fermentation are ethanol, CO2, and H2. The major cellular fatty acids of strain F-3apT are C16:0, C16:1, and C14:0. Phylogenetic analysis reveals that strain F-3apT belongs to the order Clostridiales, with less than 91% of 16S rRNA gene sequence similarity to any species with a validly published name. The total size of the genome of strain F-3apT is 2.98 Mb, and a genomic DNA G + C content is 56.78 mol%. The whole-genome phylogenetic analysis confirms that strain F-3apT forms a distinct lineage within Clostridia. We propose to assign strain F-3apT to a new species of a novel genus Anaerotalea alkaliphila gen. nov., sp. nov. The type strain is F-3apT (= KCTC 15917 T = VKM B-3406 T). [ABSTRACT FROM AUTHOR]

Increasing ethanol demand and public concerns about environmental protection promote the production of lignocellulosic bioethanol. Compared to that of starch- and sugar-based bioethanol production, the production of lignocellulosic bioethanol is water-intensive. A large amount of water is consumed during pretreatment, detoxification, saccharification, and fermentation. Water is a limited resource, and very high water consumption limits the industrial production of lignocellulosic bioethanol and decreases its environmental feasibility. In this review, we focused on the potential for reducing water consumption during the production of lignocellulosic bioethanol by performing pretreatment and fermentation at high solid loading, omitting water washing after pretreatment, and recycling wastewater by integrating bioethanol production and anaerobic digestion. In addition, the feasibility of these approaches and their research progress were discussed. This comprehensive review is expected to draw attention to water competition between bioethanol production and human use. [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]

Mathematical models of ethanol fermentation in continuous conventional bioreactor (CCBR) and continuous membrane bioreactor (CMBR) are discussed theoretically. Each of these models is a system of nonlinear equations containing nonlinear terms related to Monod model for each retention time at non-steady condition. Analytical expressions of cell growth, glucose consumption, and ethanol production are obtained using a new approach of the homotopy perturbation method. A detailed study of the parameters effects on each of the governing systems is also presented. The obtained analytical solution is shown to be in strong agreement with most reliable numerical methods. [ABSTRACT FROM AUTHOR]

• A novel strategy was proposed to breed multiple stress-tolerant strain E-158. • Ethanol production was significantly improved under different stress conditions. • Good genetic stability of E-158 was found after 30 times of sub-cultivation. • Strain E-158 had strong antioxidant defense ability. Breeding stress-tolerant industrial Saccharomyces cerevisiae strains is crucial to reduce the cost of bioethanol production. In this study, a novel strategy, atmospheric and room temperature plasma (ARTP) mutagenesis combined with genome shuffling and hybridization, was successfully applied to obtain a multiple stress-tolerant flocculating industrial S. cerevisiae strain E-158. The enhanced strain E-158 grew better under various stress conditions compared with the original strain KF-7. The concentrations of ethanol produced by strain E-158 during batch fermentation were 10.14 %–81.02 % higher than those produced by strain KF-7 under high ethanol, high temperature, and high osmosis stress conditions. The stress tolerance of E-158 kept stable even after 30 times of sub-cultivation. The lower reactive oxygen species (ROS) level and higher superoxide dismutase (SOD) and catalase (CAT) activities in strain E-158 manifested that the antioxidant defense ability of E-158 was improved and contributed to its multiple stress-tolerance. This study provided a stress-tolerant strain for industrial ethanol production and a feasible strategy for breeding multiple stress-tolerant industrial S. cerevisiae strain. [ABSTRACT FROM AUTHOR]

The yeast Dekkera bruxellensis is well-known for its adaptation to industrial ethanol fermentation processes, which can be further improved if nitrate is present in the substrate. To date, the assimilation of nitrate has been considered inefficient because of the apparent energy cost imposed on cell metabolism. Recent research, however, has shown that nitrate promotes growth rate and ethanol yield when oxygen is absent from the environment. Given this, the present work aimed to identify the biological mechanisms behind this physiological behaviour. Proteomic analyses comparing four contrasting growth conditions gave some clues on how nitrate could be used as primary nitrogen source by D. bruxellensis GDB 248 (URM 8346) cells in anaerobiosis. The superior anaerobic growth in nitrate seems to be a consequence of increased cell metabolism (glycolytic pathway, production of ATP and NADPH and anaplerotic reactions providing metabolic intermediates) regulated by balanced activation of TORC1 and NCR de-repression mechanisms. On the other hand, the poor growth observed in aerobiosis is likely due to an oxidative stress triggered by nitrate when oxygen is present. These results represent a milestone regarding the knowledge about nitrate metabolism and might be explored for future use of D. bruxellensis as an industrial yeast. Key points: • Nitrate can be regarded as preferential nitrogen source for D. bruxellensis. • Oxidative stress limits the growth of D. bruxellensis in nitrate in aerobiosis. • Nitrate is a nutrient for novel industrial bioprocesses using D. bruxellensis. [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]

To minimize waste generation in ethanol production from starchy and cellulosic feedstocks, the feasibility of stillage recycle to fermentation process was studied. For sugarcane bagasse (SCB) and palm empty fruit bunch (EFB), optimal hot-compressed water (HCW) pretreatment and enzyme hydrolysis (10% wt) gave the highest total reducing sugar (TRS) yields of 64.2% and 67.3%, respectively. Ethanol fermentation of SCB, EFB and fresh cassava by Saccharomyces cerevisiae TISTR5606 gave the highest yields of 0.31 g g−1, 0.40 g g−1, and 0.31 g g−1 TRS, respectively. For recycling of SCB and EFB stillage, a slight decline of ethanol yield was found while ethanol yield of cassava significantly increased from 60.8% to 89.9%. The ethanol yields from the 2nd recycle of cassava was still 10% higher than no recycle. Addition of 10%–20% v/v black liquor from lignocellulosic HCW pretreatment into anaerobic digestion system noticeably enhanced the chemical oxygen demand removal and methane production. Analysis of variable operating cost showed that stillage recycles for 20% for fresh cassava and 10% for SCB is cost-effective process for ethanol production. • Cassava stillage recycle significantly increased ethanol yield from 60.8% to 89.9%. • The ethanol yields from the 2nd recycle of cassava was still 10% higher than control. • Adding 10–50% of black liquor from SCB enhanced COD removal and CH 4 yield. • Adding 10–20%v/v black liquor from EFB enhanced COD removal and CH 4 yield. [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]

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 objective of this study was to assess the suitability of buckwheat grain for agricultural distillate production. The effects of the method of starch liberation on the physicochemical composition of the prepared mashes, fermentation results, the concentration of volatile compounds in the obtained distillates, and their organoleptic features, were investigated. The raw materials used were two cultivars of buckwheat grains, Panda and Kora. Both cultivars were characterized by similar starch content, however Panda cultivar had a significantly higher content of reducing sugars. Fermentation of the Kora cultivar-based mashes resulted in a higher fermentation efficiency (up to approximately 85% of the theoretical yield) compared to the Panda cultivar-based mashes (up to approx. 75%). Of the tested methods of starch liberation, the pressure-thermal treatment was revealed as superior, especially in the case of the Panda cultivar. In the case of the Kora cultivar, both the pressure-thermal method and the pressureless method of starch liberation resulted in a high process efficiency (up to 85% of the theoretical). Supplementation of the buckwheat mashes with (NH4)2HPO4 improved fermentation results. The highest scores in sensory assessment were given to distillates from mashes prepared with the pressure-thermal treatment, which contained relatively low concentrations of undesirable compounds, such as acetaldehyde and methanol, and revealed pleasant organoleptic features. [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]

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]

Fresh corn stover, which could be separated into fermentable juice and lignocellulosic bagasse, is considered as an alternative raw material for second-generation ethanol production. However, the influence of harvest time of corn stover on ethanol yield has not been evaluated yet. In this work, aiming to improve ethanol yield from fresh corn stover, the harvest time was redefined and optimized. Liquefaction plus simultaneous saccharification and co-fermentation (L + SScF) was carried out to define the realistic ethanol yields. Results showed that compared with the corn stover harvested in the end of physiological stage, the conventional harvest stage, the corn stover harvested in dent stage provided the highest theoretical ethanol yield of 9.92 t/ha (5.64 t/ha for the case that exclude xylan derives). 3.53 t/ha of ethanol was produced from the fresh stover harvested in dent stage, which was 1.64 times higher than using the stover obtained in the conventional harvest time. This study demonstrated that bio-ethanol yield was hugely influenced by harvest time of corn stover, and the stover harvested in dent stage has the highest ethanol yield. Image 1 • Different harvest times of fresh corn stover for bio-ethanol production were evaluated. • A highest theoretical ethanol yield of 9.92 t/ha was estimated in dent stage. • 3.53 t/ha of ethanol can be obtained by fermentation using the stover harvested in dent stage. [ABSTRACT FROM AUTHOR]

A previously published genome‐scale metabolic model namely iFF708 was modified to depict the metabolic flux distribution within Saccharomyces cerevisiae grown under a redox potential–controlled very high‐gravity condition. The following modifications were made: electron transport chain (ETC) and oxidative phosphorylation, proton gradient and ATP transportation, and malate–aspartate shuttle. With these modifications, this model could describe the experimental data collected from the above‐mentioned ethanol fermentation. As a result, the simulation unveiled that the P/O ratio is critical under microaerobic conditions and the malate–aspartate shuttle is inactivated due to the shortage of electron transport across mitochondria. In other words, the limited supply of oxygen suppresses the functionality of oxidative phosphorylation, tricarboxylic acid (TCA) cycle, and ETC. In terms of the glycolytic pathway, fluxes coming from glucose‐6‐phosphate and pyruvate nodes are insensitive to the changes of fermentation redox potential. As the initial glucose concentration is greater than 250 g/L, the interactive effect between the initial glucose concentration and redox potential level becomes noticeable. [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]

SPs could alleviate inhibition of phenolic acids, leading to high fermentability. • Soluble polysaccharides (SPs) were obtained from rice straw. • Xylan and glucan were the main components of SPs. • SPs enhanced the formation of polysaccharide-dependent extracellular matrix. • Extracellular matrix secreted by Saccharomyces cerevisiae maintained cellular integrity even under phenolic acid stress. • SPs increased ethanol production by S. cerevisiae. The bioconversion of rice straw into ethanol can alleviate the energy crisis and solve problems related to waste treatment. In this study, the effect of soluble polysaccharides (SPs) produced during rice straw saccharification on the formation of extracellular matrices (EMs) by the yeast Saccharomyces cerevisiae was investigated. SPs were characterized by high-performance liquid chromatography (HPLC) and fourier transform infrared spectroscopy (FT-IR). SPs reduced the inhibition of alcohol dehydrogenase activity by phenolic acids (PAs) and regulated the intracellular redox state, resulting in higher ethanol production. The results of flow cytometry, confocal laser scanning microscopy, and atomic force microscopy indicated that PAs changed microbial morphology and caused damage in microbial cell membranes. The protective effect of SPs against cell membrane damage could be attributed to the synthesis of polysaccharide-dependent extracellular matrix, which maintained cellular integrity even under phenolic acid stress. These findings provide new strategies to improve pretreatment and saccharification processes. [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]

Wheat sourdough is a common traditional fermented food that is produced worldwide. However, product quality of spontaneous sourdough is not easy to control because it depends on natural fermentation and backslopping, about which little is known, notably after ten backslopping steps. To this end, we tracked the spontaneous fermentation of three sourdoughs made from wheat flours during 32 backslopping steps for 60 days. At 24 time points, the microbial community was analyzed by both culture-dependent and culture-independent methods and its chemical constituents were assessed. Dynamic changes were observed in the microbial community, which showed a common succession pattern among the three sourdoughs at the bacterial family level and differences at the species level. The bacterial communities evolved through three phases that were driven by different groups of lactic acid bacteria (LAB) species. The dynamism among the metabolites also differed, depending on the species composition of the LAB and yeast communities. In one sourdough, the growth of Saccharomyces cerevisiae was detected along with a concentration of increased ethanol, while in the other two sourdoughs, Wickerhamomyces anomalus was detected without ethanol production. Regarding the LAB communities, two sourdoughs were eventually co-dominated by Lactobacillus plantarum and L. brevis , while the other sourdough was eventually dominated solely by the heterolactic fermentative bacterium Lactobacillus fermentum , and ethanol was produced at the same level as lactic acid. Further research is needed to determine the bacterial and yeast species involved in the fermentation of sourdough, to help improve the design and quality control of the final product. • The first report to track spontaneous sourdough in detail for 60 days. • Lactobacillus fermentum stabilized heterolactic fermentation at late stage. • Lactic acid increases until the final when two Lactobacillus species co-dominate. • Ethanol increases with sugars exhaustion when Saccharomyces cerevisiae is retrieved. [ABSTRACT FROM AUTHOR]

N-Acetyltransferase Mpr1 was originally discovered as an enzyme that detoxifies l-azetidine-2-carboxylate through its N-acetylation in the yeast Saccharomyces cerevisiae Σ1278b. Mpr1 protects yeast cells from oxidative stresses possibly by activating a novel l-arginine biosynthesis. We recently constructed a stable variant of Mpr1 (N203K) by a rational design based on the structure of the wild-type Mpr1 (WT). Here, we examined the effects of N203K on ethanol fermentation of the sake yeast S. cerevisiae strain lacking the MPR1 gene. When N203K was expressed in the diploid Japanese sake strain, its fermentation performance was improved compared to WT. In a laboratory-scale brewing, a sake strain expressing N203K produced more ethanol than WT. N203K also affected the contents of flavor compounds and organic acids. These results suggest that the stable Mpr1 variant contributes to the construction of new industrial yeast strains with improved fermentation ability and diversity of taste and flavor. [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]

Abstract Very high-gravity (VHG) worts (24 °P) supplemented with wheat gluten hydrolysates (WGH) and their ultrafiltration fractions (Mw > 1 kDa and <1 kDa fractions) were used to evaluate their effects on physiological activity and ethanol fermentation of brewer's yeast. The results demonstrated that WGH and their ultrafiltration fractions supplementations could obviously improve the biomass and viability of yeast, and further enhance the sugar utilization and ethanol production under VHG fermentation. Supplementation with Mw < 1 kDa fraction exhibited the maximum biomass (6.90 g/L dry cell), sugar utilization (79.79%) and ethanol concentration (11.88%, v/v) during VHG fermentation. Meanwhile, the addition of Mw < 1 kDa fraction significantly decreased the plasma membrane permeability and intracellular reactive oxygen species (ROS) accumulation, and increased the mitochondrial membrane potential in cells during VHG fermentation. Moreover, Mw < 1 kDa fraction supplementation caused the highest accumulations of intracellular trehalose and glycerol, which were 12.10% and 31.22% higher than the control, respectively. These results illustrated that WGH (especially Mw < 1 kDa fraction) addition was an economic and efficient method to improve physiological activity and ethanol fermentation of brewer's yeast in VHG worts. Highlights • WGH and their ultrafiltration fractions were obtained as nitrogen sources of yeast. • WGH supplementation changed nitrogen metabolism of yeast during VHG fermentation. • Biomass and ethanol production were increased by WGH addition under VHG condition. • Physiological activity of yeast was improved by WGH addition under VHG condition. • Trehalose and glycerol in yeast accumulated by WGH addition under VHG condition. [ABSTRACT FROM AUTHOR]

Abstract In this study, edible filamentous fungi Aspergillus oryzae and Rhizopus oligosporus were co-cultured with fodder yeast Candida utilis using corn thin stillage to produce feed-grade biomass, amylases, and ethanol with the purpose of backset valorization. The co-culture of A. oryzae with C. utilis inoculated after 24 h of pure fungal growth provided the most promising results, yielding 18.6 g L−1 biomass with 41 and 31% of lipid and protein, respectively, with all of the essential amino acids. The microorganisms consumed nearly 34% of the cultivation medium solids, as well as 33% of glycerol and 12% of lactic acid, which allowed them to produce ca. 4.5 g L−1 ethanol and 1.7 U mL−1 amylase. The liquid fraction of the cultivation medium was used as 200 mL L−1 backset for the production of high-solids corn mash. The final ethanol concentrations reached 78.3, 90.6 and 108.2 g L−1 in the control sample (without backset), unfermented backset addition and fermented backset addition, respectively. This suggests that the yeast-fungi co-culture for backset treatment was effective in improving the core production stage in an ethanol-producing plant. Highlights • Co-culture of fungi and yeast on thin stillage for backset valorization was studied. • 33.9% solids, 12.5% lactic acid and 33.4% glycerol removed by A. oryzae / C. utilis. • 18.6 g L−1 biomass, 1.7 U mL−1 amylase and 4.5 g L−1 ethanol produced. • Cultivation liquid used as 200 mL L−1 for high solids corn mash production. • Ethanol yield and production rate greatly improved by fermented backset use. [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]