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Economically feasible ethanol production requires efficient hydrolysis of lignocellulosic biomass and high–temperature processing to enable simultaneous saccharification and fermentation. During the lignocellulolysic hydrolysate, the yeast must encounter with a multiple of inhibitors such as heat and furfural. To solve this problem, a potential fermentative yeast strain that tolerated simultaneous multistress and enhance ethanol concentration was investigated. Twenty yeast isolates were classified into two major yeast species, namely Pichia kudriavzevii (twelve isolates) and Candida tropicalis (eight isolates). All P. kudriavzevii isolates were able to grow at high temperature (45 °C) and exhibited stress tolerance toward furfural. Among P. kudriavzevii isolates, NUCG–S3 presented the highest specific growth rate under each stress condition of heat and furfural, and multistress. Morphological changes in P. kudriavzevii isolates (NUCG–S2, NUCG–S3, NUKL–P1, NUKL–P3, and NUOR–J1) showed alteration in mean cell length and width compared to the non–stress condition. Ethanol production by glucose was also determined. The yeast strain, NUCG–S3, gave the highest ethanol concentrations at 99.46 ± 0.82, 62.23 ± 0.96, and 65.80 ± 0.62 g/l (P < 0.05) under temperature of 30 °C, 40 °C, and 42 °C, respectively. The tolerant isolated yeast NUCG–S3 achieved ethanol production of 53.58 ± 3.36 and 48.06 ± 3.31 g/l (P < 0.05) in the presence of 15 mM furfural and multistress (42 °C with 15 mM furfural), respectively. Based on the results of the present study, the novel thermos and furfural-tolerant yeast strain P. kudriavzevii NUCG–S3 showed promise as a highly proficient yeast for high–temperature ethanol fermentation. [ABSTRACT FROM AUTHOR]

Kluyveromyces markus CGMCC13907 and Saccharomyces cerevisiae AS2. 119 were selected as mixed starter cultures for fermentation of whey liquid to produce whey vinegar. Plackett-Burman Design (PBD) and Box-Behnken Design (BBD) were used to optimize the ethanol fermentation process. The results showed that the optimal ethanol fermentation process was K. markus CGMCC13907 inoculum volume 4. 0×106 CFU/mL, S. cerevisiae AS2. 119 inoculum volume 4. 5×106 CFU/ mL, fermentation time 151 h, fermentation temperature 40. 0 ×, fermentation pH value 5. 6, ginger powder dosage 0. 09 g/100 mL. Under this condition, the concentration of ethanol in fermentation liquid reached 8. 70 %vol, which increased by 56. 2% compared with that before optimization. K. markus CGMCC13907 combined with S. cerevisiae AS2. 119 could effectively solve the lactose fermentation problem in the process of making vinegar from whey, and achieve a better ethanol concentration. [ABSTRACT FROM AUTHOR]

AbstractGlobal energy demand is experiencing a notable surge due to growing energy security. Renewable energy sources, like ethanol, are becoming more viable. In the present study, the application of a PSO-PID (Particle Swarm Optimization – Proportional Integral Derivative) controller with a split-range control strategy was suggested for the regulation of temperature within the fermentation system. To optimize performance, a POS-PID controller with a split-range arrangement utilizing two control valves for hot and cold utilities was constructed. The study began by examining the open-loop dynamic response of the system to inlet temperature and concentration disturbances during ethanol production fermentation. Subsequently, a transfer function model was developed through linearization at the steady-state operating point. The split-range controller structure, implemented by optimizing the PSO-PID controller parameters using PSO, effectively demonstrated temperature control in simulations of a nonlinear model. In this investigation, the ethanol fermentation system was modeled as a CSTR using a modified Monod equation for microbial growth kinetics. Various dynamic behavioral disturbances were explored and verified in the model with plant data in this study. The simulation model results were validated through plant data. The proposed method showed superior closed-loop performance with respect to errors, with the actuators proving to be effective than other reported methods for temperature control. [ABSTRACT FROM AUTHOR]

Thermophilic actinomycetes are commonly found in extreme environments and can thrive and adapt to extreme conditions. These organisms exhibit substantial variation and garnered significant interest due to their remarkable enzymatic activities. This study evaluated the potential of Streptomyces griseorubens NBR14 and Nocardiopsis synnemataformans NBRM9 strains to produce thermo-stable amylase via submerged fermentation using wheat and bean straw. The Box-Behnken design was utilized to determine the optimum parameters for amylase biosynthesis. Subsequently, amylase underwent partial purification and characterization. Furthermore, the obtained hydrolysate was applied for ethanol fermentation using Saccharomyces cerevisiae. The optimal parameters for obtaining the highest amylase activity by NBR14 (7.72 U/mL) and NBRM9 (26.54 U/mL) strains were found to be 40 and 30 °C, pH values of 7, incubation time of 7 days, and substrate concentration (3 and 2 g/100 mL), respectively. The NBR14 and NBRM9 amylase were partially purified, resulting in specific activities of 251.15 and 144.84 U/mg, as well as purification factors of 3.91 and 2.69-fold, respectively. After partial purification, the amylase extracted from NBR14 and NBRM9 showed the highest activity level at pH values of 9 and 7 and temperatures of 50 and 60 °C, respectively. The findings also indicated that the maximum velocity (Vmax) for NBR14 and NBRM9 amylase were 57.80 and 59.88 U/mL, respectively, with Km constants of 1.39 and 1.479 mM. After 48 h, bioethanol was produced at concentrations of 5.95 mg/mL and 9.29 mg/mL from hydrolyzed wheat and bean straw, respectively, through fermentation with S. cerevisiae. Thermophilic actinomycetes and their α-amylase yield demonstrated promising potential for sustainable bio-ethanol production from agro-byproducts. [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]

Background: Production of cheese whey in the EU exceeded 55 million tons in 2022, resulting in lactose-rich effluents that pose significant environmental challenges. To address this issue, the present study investigated cheese-whey treatment via membrane filtration and the utilization of its components as fermentation feedstock. A simulation model was developed for an industrial-scale facility located in Italy's Apulia region, designed to process 539 m3/day of untreated cheese-whey. The model integrated experimental data from ethanolic fermentation using a selected strain of Kluyveromyces marxianus in lactose-supplemented media, along with relevant published data. Results: The simulation was divided into three different sections. The first section focused on cheese-whey pretreatment through membrane filtration, enabling the recovery of 56%w/w whey protein concentrate, process water recirculation, and lactose concentration. In the second section, the recovered lactose was directed towards fermentation and downstream anhydrous ethanol production. The third section encompassed anaerobic digestion of organic residue, sludge handling, and combined heat and power production. Moreover, three different scenarios were produced based on ethanol yield on lactose (YE/L), biomass yield on lactose, and final lactose concentration in the medium. A techno-economic assessment based on the collected data was performed as well as a sensitivity analysis focused on economic parameters, encompassing considerations on cheese-whey by assessing its economical impact as a credit for the simulated facility, dictated by a gate fee, or as a cost by considering it a raw material. The techno-economic analysis revealed different minimum ethanol selling prices across the three scenarios. The best performance was obtained in the scenario presenting a YE/L = 0.45 g/g, with a minimum selling price of 1.43 €/kg. Finally, sensitivity analysis highlighted the model's dependence on the price or credit associated with cheese-whey handling. Conclusions: This work highlighted the importance of policy implementation in this kind of study, demonstrating how a gate fee approach applied to cheese-whey procurement positively impacted the final minimum selling price for ethanol across all scenarios. Additionally, considerations should be made about the implementation of the simulated process as a plug-in addition in to existing processes dealing with dairy products or handling multiple biomasses to produce ethanol. [ABSTRACT FROM AUTHOR]

In this article, the problem of real‐time estimation of the fermentative ethanol process is tackled. The considered observer is a model‐based technique that is robust regarding the model parameter uncertainties and inline noisy measurements. An unstructured kinetic model was used to describe the production of ethanol in a batch bioreactor for Saccharomyces cerevisiae. The biomass concentration was selected as the measured bioreactor´s output via an inline device, where the estimate variables were the substrate and ethanol concentrations. An experimental prototype was constructed to demonstrate the observer's real‐time performance. The experimental results show that the robust, smooth sliding mode observer performs better than the standard proportional sliding mode observer. [ABSTRACT FROM AUTHOR]

Very high gravity (VHG) ethanol fermentation at low temperatures can be a way to obtain wines with high ethanol content (> 15 °GL). The production of vinasse is lower, compared to typical industrial conditions, which reduces the costs of storage and transport. However, there is greater heat generation during cell growth, resulting in an increased requirement for cooling water. One promising way to cool the vat is to use CO2 stripping, which removes heat by vaporization of the ethanol and water in the broth. Therefore, the aim of the present study was to find suitable operating conditions, considering the gas flow rate ( F CO 2 ) and the stripping start ( t start ) and stop ( t stop ) times, that could reduce the volume of water required for temperature control. Simulations of extractive fermentations at 28 and 34 °C, with must substrate concentration ( C SM ) of 300 g/L, were performed to obtain F CO 2 , t start , and t stop . Experimental validations showed water volume reductions of 66.4% (28 °C) and 67.0% (34 °C), compared to the corresponding conventional ethanol fermentations. An extractive VHG fermentation at 28 °C, with C SM =372 g/L, was carried out under the conditions obtained in the simulations. The results showed a 61.9% reduction in water volume and a total ethanol content of 15 °GL. The gas stripping technique applied to VHG fermentation at low temperature was proved to be environmentally friendly, since it reduced the volume of vinasse generated and saved water, which could reduce the number of heat exchangers and the costs associated with their maintenance. [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]

[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]

Fuel ethanol has drawn extensive attention as renewable energy. However, modeling the fuel ethanol batch fermentation process is still a critical task. The unstructured kinetic model (UKM) is often utilized to model the process, but it encounters two problems due to the large differences in initial glucose concentrations. First, the UKM has poor predictions of the yeast growth, which is a crucial production index. Second, the kinetic parameters of the UKM are time-varying because of the changing environmental conditions. The constant manually set kinetic parameters affect the prediction accuracy. To tackle the problems, we propose a dynamic hybrid model of the fuel ethanol fermentation process. First, a biomass concentration prediction model based on extreme gradient boosting is developed. It predicts the values of biomass concentrations and mycelium growth rate as supplementary mechanism knowledge. Then, we present an artificial neural network-based model to determine the time-varying kinetic parameters. Our model can accurately predict the time series of biomass, ethanol, and glucose concentrations, with RMSEs reaching 0.3323, 1.9295, and 3.0540. Experimental results show that the dynamic hybrid model performs with satisfactory accuracy in modeling the fuel ethanol fermentation process. [ABSTRACT FROM AUTHOR]

Cassava (Manihot esculenta Crantz) leaves contain high protein content (ca 20%). This study aimed to evaluate application of the leaves as a nitrogen source for Saccharomyces cerevisiae in ethanol fermentation by comparing it with general nitrogen sources in yeast malt (YM) media. Mild pretreatments: liquid hot water, alkaline, and dilute acid, were conducted to extract amino nitrogen from the leaves while minimizing degradation. The liquid fraction from the liquid hot water pretreatment (CLWP) showed the highest amino nitrogen content of 271 ± 25 mg of N/L. Most free amino acids in CLWP were glutamic acid (22 g/kg leaves) and aspartic acid (20 g/kg leaves). After 24 h of fermentation, the equal glucose and nitrogen concentration media with CLWP gave 5 times higher ethanol content (10% v/v) than the absence of CLWP conditions (2% v/v). Free amino acids in the leaves provided a greater benefit to yeasts in ethanol production than other traditional chemical sources. Cassava leaves had high potential to be used as a nitrogen source for ethanol fermentation. [ABSTRACT FROM AUTHOR]

• SCF as a kind of periodic operation is analyzed for its superiority over the steady-state counterpart. • SCF as a kind of impulsive control is evaluated for possible repetition property in long-term operation. • Optimal on-off operation strategies are formulated with guaranteed periodic stability and superiority. Fuel ethanol is highlighted for being renewable and carbon neutral, but a multi-scale challenge exists that hampers its role as a future energy substitute, and with the breakthrough of cellulose pretreatment and enzyme hydrolysis technology, fermentation itself has become one of the main limiting factors for process enhancement. To tackle the problem, this paper studies periodic operation strategies to improve process performance and avoid possible instabilities. Firstly, superiority by periodic operation over the corresponding steady-state operation is verified. Then, to settle the problem of possible instabilities under impulsive control, stability of state-impulsive control is conducted and for the studied case, any self-cycling fermentation starts from batch mode with 50 % discharge-and-refill portion exhibits superior repeatability property, which allows continuous fermentation to operate under very slow overall dilution rate to cope with the extreme slow fermentation rate. Finally, on-off operation problem is formulated that is governed by a multidimensional nonlinear system, affine to the manipulated variable that is under the isoperimetric constraint; with the use of Pontryagin maximum principle, the optimal synthesis of the optimal strategies under integral constraint is computed out, and a practically plausible on-off operation strategy for ethanol fermentation is formulated with guaranteed periodic stability and optimality. [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]

[Display omitted] • A butanol concentration of 11.7 g /L was achieved by Clostridium using apple pomace. • The process conditions optimization allowed to avoid the undesirable acid crash. • Lower temperature and higher pH and CaCO 3 concentration promotes butanol production. • Avoiding centrifugation of the hydrolysate reduces process costs and time. • The hydrolysate with solids was comparable to the supernatant as substrate. Apple pomace (AP) is a lignocellulosic residue from the juice and cider industries that can be valorized in a multi-product biorefinery to generate multiple value-added compounds, including biofuels such as butanol. Butanol is produced biologically by acetone-butanol-ethanol (ABE) fermentation using bacteria of the genus Clostridium from sugar-based feedstocks. In this study, AP hydrolysate was used as a substrate for producing butanol by ABE fermentation. Various environmental factors influence the amount of butanol produced, but only under certain conditions the so-called 'acid crash', an undesirable phenomenon characterized by a total arrest of cell growth and solvent production, can be avoided. Operational parameters that may influence the prevention of acid crash occurrence, such as pH, CaCO 3 concentration and culture temperature, were optimized in C. beijerinckii CECT 508 cultures applying a Box-Behnken experimental design. The mathematical model of the fermentation found the optimal conditions of pH 7, 6.8 g/L of CaCO 3 and 30 °C, and this was validated in an independent experiment carried out at the optimal conditions, reaching 10.75 g/L of butanol. Also, the comparison of butanol production between the supernatant of the AP hydrolysate (10.57 g/L) and the full hydrolysate with solids (11.69 g/L) indicated that it is possible to eliminate the centrifugation step after hydrolysis, which may allow to reduce process costs and the full utilization of apple pomace, aiming a zero-waste approach. [ABSTRACT FROM AUTHOR]

High-temperature ethanol fermentation by thermotolerant yeast is considered a promising technology for ethanol production, especially in tropical and subtropical regions. In this study, optimization conditions for high-temperature ethanol fermentation of pineapple waste hydrolysate (PWH) using a newly isolated thermotolerant yeast, Saccharomyces cerevisiae HG1.1, and the expression of genes during ethanol fermentation at 40 °C were carried out. Three independent variables, including cell concentration, pH, and yeast extract, positively affected ethanol production from PWH at 40 °C. The optimum levels of these significant factors evaluated using response surface methodology (RSM) based on central composite design (CCD) were a cell concentration of 8.0 × 107 cells/mL, a pH of 5.5, and a yeast extract concentration of 4.95 g/L, yielding a maximum ethanol concentration of 36.85 g/L and productivity of 3.07 g/L. Gene expression analysis during high-temperature ethanol fermentation using RT–qPCR revealed that the acquisition of thermotolerance ability and ethanol fermentation efficiency of S. cerevisiae HG1.1 are associated with genes responsible for growth and ethanol stress, oxidative stress, acetic acid stress, DNA repair, the pyruvate-to-tricarboxylic acid (TCA) pathway, and the pyruvate-to-ethanol pathway. [ABSTRACT FROM AUTHOR]

A high sugar concentration is used as a starting condition in alcoholic fermentation by budding yeast, which shows changes in intracellular state and cell morphology under conditions of high-sugar stress. In this study, we developed artificial intelligence (AI) models to predict ethanol yields in yeast fermentation cultures under conditions of high-sugar stress using cell morphological data. Our method involves the extraction of high-dimensional morphological data from phase contrast images using image processing software, and predicting ethanol yields by supervised machine learning. The neural network algorithm produced the best performance, with a coefficient of determination (R 2) of 0.95, and could predict ethanol yields well even 60 min in the future. Morphological data from cells cultured in low-glucose medium could not be used for accurate prediction under conditions of high-glucose stress. Cells cultured in high-concentration glucose medium were similar in terms of morphology to cells cultured under high osmotic pressure. Feeding experiments revealed that morphological changes differed depending on the fermentation phase. By monitoring the morphology of yeast under stress, it was possible to understand the intracellular physiological conditions, suggesting that analysis of cell morphology can aid the management and stable production of desired biocommodities. [ABSTRACT FROM AUTHOR]

Removing most of the water in the acetone + n-butanol + ethanol (ABE fermentation broth can reduce energy consumption and improve the biobutanol market competitiveness. Understanding the dehydration process of ethanol, acetone, and n-butanol can guide the fermentation process for the subsequent separation, which led to an investigation into the salting-out effects of K2CO3 on aqueous ethanol solution, aqueous acetone solution and n-butanol+water system at various temperatures. Elevating the salt concentration has the potential to decrease the water content of these solutes as well as the content of ethanol or acetone and n-butanol in the salt-free aqueous phase. The distribution and selectivity coefficients of ABE were also enhanced. As a result, the recovery and dehydration ratio of ethanol or acetone, or n-butanol, was also improved. The strong hydrophilicity of acetone and ethanol makes the recovery and dehydration ratio of n-butanol difficult. On the same basis(50% K2CO3), the dehydration ratios of ethanol, acetone, and n-butanol were 91.43%, 96.21%, and 97.52%, respectively. Thus, the dehydration capacity gave the following trend: n-butanol>acetone>ethanol. By raising the temperature，it was possible to increase the amount of ethanol，acetone，or n-butanol in the organic phase while decreasing their amounts in the aqueous phase. The ratio of n-butanol's recovery and dehydration can be improved by raising the temperature. [ABSTRACT FROM AUTHOR]

Simple Summary: Hyperthermophilic Thermotoga spp. are promising candidates for the metabolic engineering of cellulosic ethanol producing strains. However, Thermotoga spp. are hydrogen producers, and none of them have been found to produce significant amount of ethanol. In this study, we focused on the enzymes responsible for the part of the ethanol production pathway from ac-CoA to ethanol. Aldehyde dehydrogenases (Aldhs) and alcohol dehydrogenases (Adhs) are the vital enzymes involved in the metabolism of ethanol in Thermotoga spp.. However, the biochemical properties of a number of Adhs related to ethanol formation and consumption have not been identified until now. The aim of this study was to determine the role of putative Adhs in T. neapolitana (Tne) in the pathway from ac-CoA to ethanol. We found that the Fe-AAdh (encoded by CTN_0580) and Fe-Adh2 (encoded by CTN_1756) were the main enzymes responsible for ethanol production in Tne. While Zn-Adh (encoded by CTN_0257) was identified as the main protein responsible for ethanol consumption in the acid environment and Fe-Adh1 (encoded by CTN_1655) played a minor role in ethonal production and consumption in Tne. Basing on these results, it will be helpful to construct and assemble a novel hyperthermophilic strain to produce cellulosic ethanol. Hyperthermophilic Thermotoga spp. are candidates for cellulosic ethanol fermentation. A bifunctional iron-acetaldehyde/alcohol dehydrogenase (Fe-AAdh) has been revealed to catalyze the acetyl-CoA (Ac-CoA) reduction to form ethanol via an acetaldehyde intermediate in Thermotoga neapolitana (T. neapolitana). In this organism, there are three additional alcohol dehydrogenases, Zn-Adh, Fe-Adh1, and Fe-Adh2, encoded by genes CTN_0257, CTN_1655, and CTN_1756, respectively. This paper reports the properties and functions of these enzymes in the fermentation pathway from Ac-CoA to ethanol. It was determined that Zn-Adh only exhibited activity when oxidizing ethanol to acetaldehyde, and no detectable activity for the reaction from acetaldehyde to ethanol. Fe-Adh1 had specific activities of approximately 0.7 and 0.4 U/mg for the forward and reverse reactions between acetaldehyde and ethanol at a pHopt of 8.5 and Topt of 95 °C. Catalyzing the reduction of acetaldehyde to produce ethanol, Fe-Adh2 exhibited the highest activity of approximately 3 U/mg at a pHopt of 7.0 and Topt of 85 °C, which were close to the optimal growth conditions. These results indicate that Fe-Adh2 and Zn-Adh are the main enzymes that catalyze ethanol formation and consumption in the hyperthermophilic bacterium, respectively. [ABSTRACT FROM AUTHOR]

The aim of this study was to analyze the effects of 1‐methylcyclopropene (1‐MCP) on ethanol fermentation of Nanguo pears during ripening. Pears were exposed to 1 µl/L 1‐MCP and stored at 20 ± 2°C. Our data indicated that postharvest application of 1‐MCP maintained flesh firmness and reduced ethylene production and respiration rate during storage compared with untreated fruits. 1‐MCP treatment delayed the second glucose peak during fruit ripening. The contents of pyruvate and acetyl‐CoA were generally reduced by 1‐MCP treatment, and at the same time, their peaks were delayed by it during storage compared with controls. The contents of citric acid (CA) and oxaloacetate (OA) were increased by 1‐MCP, whereas the contents of acetaldehyde and ethanol were reduced during the whole storage period compared with controls. Activities of alcohol dehydrogenase (ADH) and pyruvate decarboxylase (PDC) were reduced by application of 1‐MCP during the early stage of storage, and the appearance of their peak activities was also delayed after treatment with 1‐MCP. These data showed that postharvest application of 1‐MCP could effectively delay the production of the "alcohol taste" of Nanguo pears during ripening. Practical applications: Nanguo pear is one of the most common cultivars that widely grow in northeast China. It is preferred by many consumers for its unique "alcohol taste", which is mainly produced through ethanol fermentation during ripening. Until now, the mechanisms for regulating ethanol fermentation in ripening Nanguo pears are still unclear. Our data indicated that postharvest application of the ethylene action inhibitor 1‐MCP could effectively delay the production of the "alcohol taste" of Nanguo pears during ripening. The data from this study can provide reference data for maintaining the quality of postharvest Nanguo pears. [ABSTRACT FROM AUTHOR]

Simultaneous saccharification and fermentation (SSF) is effective for minimizing sugar inhibition during high solids fermentation of biomass solids to ethanol. However, fungal enzymes used during SSF are optimal between 50 and 60 °C, whereas most fermentative yeast, such as Saccharomyces cerevisiae, do not tolerate temperatures above 37 °C. Kluyveromyces marxianus variant CBS 6556 is a thermotolerant eukaryote that thrives at 43 °C, thus potentially serving as a promising new host for SSF operation in biorefineries. Here, we attempt to leverage the thermotolerance of the strain to demonstrate the application of CBS 6556 in a high solids (up to 20 wt% insoluble solid loading) SSF configuration to understand its capabilities and limitations as compared to a proven SSF strain, S. cerevisiae D5A. For this study, we first pretreated hardwood poplar chips using Co-Solvent Enhanced Lignocellulosic Fractionation (CELF) to remove lignin and hemicellulose and to produce cellulose-enriched pretreated solids for SSF. Our results demonstrate that although CBS 6556 could not directly outperform D5A, it demonstrated similar tolerance to high gravity sugar solutions, superior growth rates at higher temperatures and higher early stage ethanol productivity. We discovered that CBS 6556's membrane was particularly sensitive to higher ethanol concentrations causing it to suffer earlier fermentation arrest than D5A. Cross-examination of metabolite data between CBS 6556 and D5A and cell surface imaging suggests that the combined stresses of high ethanol concentrations and temperature to CBS 6556's cell membrane was a primary factor limiting its ethanol productivity. Hence, we believe K. marxianus to be an excellent host for future genetic engineering efforts to improve membrane robustness especially at high temperatures in order to achieve higher ethanol productivity and titers, serving as a viable alternative to D5A. [ABSTRACT FROM AUTHOR]

Biobutanol is known for its potential as a biofuel and for having various other industrial applications. However, technical and economic constraints still restrict its commercial application. Biobutanol is produced via acetone, butanol, and ethanol (ABE) fermentation, in which acetone and ethanol are also produced, mainly by Clostridium sp.; however, it is toxic to the cells. Efforts have been made to improve the process by separating butanol from the fermentation broth. This work presents an overview of the main processes reported in ABE separation in the literature, focusing on the pervaporation approach. Some of the latest developments in the field are stated, aiming at comparing the separation processes. [ABSTRACT FROM AUTHOR]

Dark malts used in the production of brewing wort affect the ethanol fermentation process, the phenolic content, antioxidant capacity and the physiology of yeast cells. An innovative element of this research is the combination of investigating the effect of beer wort color modulated by the use of dark specialty malts on the course and effects of fermentation and the characteristics of post-fermentation yeast biomass of brewer's strains with different characteristics. Dark and pale beer were obtained. The beers had different ethanol contents (4.51–5.79% v/v), resulting from real (62.29–80.36%) and apparent (75.37–98.26%) attenuation levels. Metabolic and morphological differences were demonstrated in the brewer's yeast strains used. S. cerevisiae var. diastaticus was distinguished by its ability to ferment dextrin, resulting in the highest ethanol content in beers. The total phenolic content in beer depends on the color of the wort and the yeast strain used (244.48–547.56 mg of gallic acid/L). Dark beers show higher ferric ion reduction ability (FRAP) and antioxidant capacity (ABTS•+) than pale beers fermented with the same yeast strains. Through biomass analysis, differences in yeast cell physiology depending on yeast strain and beer wort color were also revealed. [ABSTRACT FROM AUTHOR]

The consolidation of cellulosic ethanol on the market is fundamental to mitigate the consumption of fuels from fossil sources and to reduce the impact caused by the large generation of agro-industrial waste. In order to achieve this objective, some challenges of cellulosic ethanol technology must be overcome, including the improvement of the cellulosic ethanol production steps. Several studies propose the use of poly(ethylene glycol) (PEG) and non-ionic surfactants (such as Tween 80, Tween 20, and Triton X-100) as a way to increase cellulosic ethanol titers. The benefits attributed to the PEG and non-ionic surfactants go beyond the increase of the concentration of free cellulases during enzymatic hydrolysis. Successful cases of pretreatments of lignocellulosic biomasses assisted by PEG and surfactants and the detoxification of inhibitor-rich hydrolysates with PEG reveal the existence of a plethora of positive mechanisms. Therefore, the present review article is focused on the benefits and mechanisms involved in the addition of PEG and non-ionic surfactants in the pretreatment, enzymatic hydrolysis, and ethanol fermentation steps. Interactions between additives and lignin as well as schemes based on high PEG concentrations were also discussed in detail. [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]

Fuel ethanol has great potential as a substitute for non-renewable energy. However, modeling the pragmatic industrial process of fuel ethanol fermentation continues to be an exceedingly formidable challenge. First, the kinetic parameters in pure mechanism modeling ignore the significant differences among batches. Second, the prediction of ethanol and sugar concentrations is highly dependent on the yeast concentration, which is often missing due to factory technology. Thus, we propose a dynamic hybrid model to realize the accurate prediction of ethanol and sugar concentrations. First, the kinetic parameter extractor based on long short-term memory models patterns of kinetic parameters and performs as a generator. Second, yeast experiments are conducted in the laboratory, and an adversarial generation of the yeast module is designed to realize yeast concentration generation, forcing the distribution of generated yeast concentrations near the distribution of laboratory ones. Finally, our proposed differential equation module decoder supplements vital mechanisms. Experimental results show that our model is biologically significant with low prediction errors. • The dynamic hybrid model of the fermentation process is biologically interpretable. • LSTM-based kinetic parameter extractor models the patterns of kinetic parameters. • AGYM ameliorates the biological significance issue caused by the missing data. • The differential equation module decoder provides the vital and basic mechanism. • Experimental results demonstrate the effectiveness of the hybrid model. [ABSTRACT FROM AUTHOR]

Clostridium beijerinckii population branches into metabolically diverse cell types in batch cultures. Here, we present a new kinetic model of C. beijerinckii 's Acetone-Butanol-Ethanol fermentation that considers three cell types: producers of acids (acidogenic), consumer of acids and producers of solvents (solventogenic), and spores cells. The model accurately recapitulates batch culture data. Also, the model estimates cell type-specific kinetic parameters, which can be helpful to improve the operation of the ABE fermentation and give a framework to study acidogenic and solventogenic metabolic pathways. To exemplify the latter, we used a constraint-based model to study how the ABE pathways are used among acidogenic and solventogenic cell types. We found that among both cell types, glycolytic production of ATP and consumption of NAD+ varies widely during the fermentation, with their maximum production/consumption rates happening when acidogenic and solventogenic growth rates were at their highest. However, acidogenic cells use the ABE pathway to contribute with an extra 12.5% of the total production of ATP, whereas solventogenic cell types use the ABE pathway to supply more than 75% of the demand for NAD+, alternating between the production of lactate and butyrate, being both coupled to the production of NAD+. • A novel kinetic model of ABE fermentation that considers various cell types. • The model simulates complex temporal trends of acids and solvents in ABE fermentation. • This approach combines experimental measurements with in silico metabolic and kinetic modeling. • Estimation of cell type-specific exchange rates allows studying how glycolytic production of ATP and consumption of NAD+ vary during fermentation. [ABSTRACT FROM AUTHOR]

Straw fermented fuel ethanol is a complex process with multivariable, large lag, and strong nonlinearity. It is difficult to directly measure the key parameters such as ethanol concentration and cell concentration online. Aiming at the problem, a soft sensing model of straw fermented ethanol based on improved support vector regression (SVR) is proposed. Based on the analysis of the process of ethanol production from straw fermentation, the Bayesian method is used to optimize the support vector regression (BSVR). And the concepts of generation a priori and generation likelihood are introduced to optimize the data prediction model. The comparative experiment of model training and testing is carried out. The simulation results show that the proposed BSVR method is better than SVR. It can improve the generalization ability of data and the anti-interference of the model, and its prediction accuracy and stability are higher. [ABSTRACT FROM AUTHOR]

In the industrial fuel ethanol process, the initial feed conditions, which are static variables, and each control operation, which is dynamic variable and is changing during the producing process, have an impact on the concentration of ethanol out of the tank. Developing the accurate concentration model of ethanol out of the tank with the static variables and as early as possible dynamic variables is a challenging work and is useful in analyzing and optimizing the production process. Given that the ethanol fermentation process is multiphase and dynamic, a block concentration model of ethanol out of the tank based on multilayer perceptron (MLP) and long short-term memory (LSTM) is proposed to deal with the coexistence state of the static variables and the dynamic variables. A Channel-Squeeze-and-Excitation (CSE) module is constructed to solve the problem of high-dimensional input and low-dimensional output caused by the block model. The proposed model is applied for the industrial ethanol fermentation process. The results show that CSE-MLSTM is significantly different from other prediction models and improves the prediction accuracy. Temperature control experiments and ablation experiments effectively verify the reliability and effectiveness of CSE-MLSTM. • Use MLP and LSTM for static and dynamic data in the model respectively. • Accurate and universal model for predicting ethanol concentration out of the tank. • The channel-squeeze-and-excitation (CSE) to address the high-dimensional input. • CSE-MLSTM greatly improves the prediction accuracy and generalization performance. • Temperature control experiments to verify the validity of the model. [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]

Biobutanol has been identified as a promising future biofuel. However, generally the extraction and separation of biobutanol from the fermentation mixture is a costly process. Therefore, the idea of using acetone-butanol-ethanol (ABE) mixture directly as biofuel were proposed to eliminate the recovery process. ABE has been identified as a promising future biofuel. The feedstocks play an important role in the feasibility of ABE as a fuel. Lignocellulosic biomass is seen as a promising feedstock for the production of biofuels. Thus, in this review, ABE biofuel is been summarized from three aspects namely (i) selection of feedstocks, (ii) microbial selection and (iii) hydrolysis, fermentation, and purification techniques. Anaerobic fermentation together with commonly employed recovery processes are discussed in the second part of this review. This review concludes with different challenges and future research in ABE fermentation that can pave the way for future commercialization of this promising biofuel. [ABSTRACT FROM AUTHOR]

Protein tyrosine nitration (PTN), in which tyrosine (Tyr) residues on proteins are converted into 3-nitrotyrosine (NT), is one of the post-translational modifications mediated by reactive nitrogen species (RNS). Many recent studies have reported that PTN contributed to signaling systems by altering the structures and/or functions of proteins. This study aimed to investigate connections between PTN and the inhibitory effect of nitrite-derived RNS on fermentation ability using the yeast Saccharomyces cerevisiae. The results indicated that RNS inhibited the ethanol production of yeast cells with increased intracellular pyruvate content. We also found that RNS decreased the activities of pyruvate decarboxylase (PDC) as a critical enzyme involved in ethanol production. Our proteomic analysis revealed that the main PDC isozyme Pdc1 underwent the PTN modification at Tyr38, Tyr157, and Tyr344. The biochemical analysis using the recombinant purified Pdc1 enzyme indicated that PTN at Tyr157 or Tyr344 significantly reduced the Pdc1 activity. Interestingly, the substitution of Tyr157 or Tyr344 to phenylalanine, which is no longer converted into NT, recovered the ethanol production under the RNS treatment conditions. These findings suggest that nitrite impairs the fermentation ability of yeast by inhibiting the Pdc1 activity via its PTN modification at Tyr157 and Tyr344 of Pdc1. [ABSTRACT FROM AUTHOR]

Several industries require getting information of products as soon as possible during fermentation. However, the trade-off between sensing speed and data quantity presents challenges for forecasting fermentation product yields. In this study, we tried to develop AI models to forecast ethanol yields in yeast fermentation cultures, using cell morphological data. Our platform involves the quick acquisition of yeast morphological images using a nonstaining protocol, extraction of high-dimensional morphological data using image processing software, and forecasting of ethanol yields via supervised machine learning .We found that the neural network algorithm produced the best performance, which had a coefficient of determination of >0.9 even at 30 and 60 min in the future. The model was validated using test data collected using the CalMorph-PC(10) system, which enables rapid image acquisition within 10 min. AI-based forecasting of product yields based on cell morphology will facilitate the management and stable production of desired biocommodities. [ABSTRACT FROM AUTHOR]

This study investigated cellulosic ethanol production from sugar cane bagasse (SCB) pretreated by triethylbenzyl ammonium chloride/lactic acid (TEBAC/LA) deep eutectic solvent (DES). The results showed that the pretreatment of SCB with TEBAC/LA DES at 120 °C for 4 h with 1:15 (solid to liquid ratio) resulted in the best cellulose digestibility (88.23 ± 1.24%), which was approximately 228% higher than that of untreated SCB. Furthermore, the maximum cellulosic ethanol concentration of 16.84 g/L was achieved using glucose (36.06 g/L) and xylose (7.36 g/L). Moreover, the ethanol productivity and yield were 0.70 g/(L·h) and 0.42 g/g fermentable sugar, respectively. The efficient bioconversion was ascribed to the remarkable delignification (88.72 ± 1.63%), xylan removal (73.93 ± 0.17%), along with optimum cellulose recovery (95.89 ± 1.54%). Importantly, the enzymatic hydrolysis digestibility remained unchanged after 5 times DES recycling process. Overall, it also provided an insight into the efficient SCB biorefinery of DES systems. [Display omitted] [ABSTRACT FROM AUTHOR]

• Thermally self-sufficient heat pump-assisted dividing-wall column for biofuel recovery. • Eco-efficient product recovery after isopropanol – butanol – ethanol (IBE) fermentation. • Cost-effective (0.126 $/kgIBE) and energy-efficient (0.673 kWeh/kgIBE) downstream processing. • Heat pumping and heat integration for electrification of industrial biotechnology. • Large-scale downstream process for sustainable industrial biofuels production. Isopropanol-butanol-ethanol (IBE) fermentation is a superior biofuel production technology as compared to acetone-butanol-ethanol (ABE) fermentation due to the better fuel properties of the obtained products. However, low product concentrations, thermodynamic constraints and the presence of microorganisms lead to complex downstream processing that limits the competitiveness of this biofuel production method. Thus, this original research proposes a novel thermally self-sufficient and eco-efficient downstream process for industrial-scale recovery after IBE fermentation (74 ktonne/y capacity), from a highly dilute broth (>97 wt% water). Gas stripping and heat pump-assisted vacuum evaporation were implemented to separate valuable products from most of the broth. Furthermore, an advanced highly integrated heat pump-assisted azeotropic dividing-wall column was designed to recover high-purity (99 wt%) butanol biofuel and isopropanol – ethanol fuel supplement (89 wt%). The proposed purification process recovers over 99 % of biofuel products in a cost-effective (0.130 $/kg IBE) and energy-efficient way (0.673 kW e h/kg IBE) while allowing full recycle of biomass and most of the separated water. Besides improving yield by continuously recovering the inhibitory products, fermentation can be further enhanced by avoiding biomass loss and reducing water requirements. Lastly, the implemented energy-saving techniques ensure complete electrification of the proposed IBE recovery process. Therefore, the original results of this research study significantly contribute to the development of sustainable biofuel production processes. [Display omitted] [ABSTRACT FROM AUTHOR]

In fermentations with high cell density, the high volume occupied by the cells can impair the robustness of models. In this work, the cell volume was considered in the development of mass balances for fed-batch ethanol fermentations, which can be useful for industrial applications. Batch fermentation was modeled using a classical model, which ignores the volume occupied by the cells, and considering the volume occupied by the cells, with no significant difference observed between the estimated kinetic parameters. High cell density fed-batch fermentations were simulated and experimentally validated for different must substrate concentrations of 300 g·L−1 and 375 g·L−1 (very high gravity fermentation) in bench-scale assays. Comparison using different statistical indexes showed that the models had equal performance in predicting the profiles of cells and ethanol. However, for prediction of the substrate concentration, the proposed model presented better indexes, indicating that the cell volume should be considered in the development of fed-batch ethanol fermentation modeling. This approach could be used as an important tool for the improvement of optimization routines and process control, especially for the application of very high gravity fed-batch ethanol fermentations on an industrial scale, which allows an increase of ethanol production around 20% compared to the conventional process. Besides, it can be used in techno-economic assessments providing more accurate results thereby bringing economic gains. [Display omitted] • High cell density in fed-batch ethanol fermentation interferes in mathematical modeling. • Mass balance taking into account the cell volume (intrinsic approach) improved the modeling. • The use of the intrinsic model reduces design, control and process optimization errors. • The intrinsic model can contribute to the improvement of very high gravity fed-batch fermentations. [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]

This work evaluated the effectiveness of ternary deep eutectic solvents (DES) composed of cholinium chloride (ChCl), lactic acid (LA) and a diol (ethylene glycol – EG, or 1,6-hexanediol – HEX) in the pretreatment of rice straw (RS) towards the production of biobutanol. The most promising results were obtained with ChCl:LA:EG 1:5:5 at 120 °C for 4 h, which enabled the highest conversion of biomass polysaccharides into glucose and xylose up to 89.3 % and 53.6 % yields, respectively. Subsequently, the produced sugars were efficiently converted into biobutanol through the acetone-butanol-ethanol (ABE) fermentation process, resulting in the production of 95.7 g butanol/kg RS as one of the highest values reported in literature. Thus, the application of the ternary DES ChCl:LA:EG 1:5:5 represents a competitive and environmentally friendly pathway for RS valorization in comparison to conventional processes. [Display omitted] [ABSTRACT FROM AUTHOR]

Ionic liquids (ILs) are emerging as promising solvents for reducing the structural recalcitrance of lignocellulosic materials suitable for enzymatic saccharification. The present study investigated the use of ionic liquid [C 2 mim]oAc under alkaline aqueous conditions to form a system dissolving lignin selectively and to recover carbohydrate fraction of the corncob more efficiently. The optimum pretreatment condition was 120 °C, 6% ammonia, 60% ionic liquid, 15:1 liquid to solid ratio and 120 min treatment time. The results showed 68% delignification with a subsequent decrease in the crystallinity of substrate from 62% to 29%. Under optimized pretreatment conditions, the cellulose rich corncob showed 91% hydrolysability. The material balance analysis revealed the maximum sugar and ethanol production of 0.659 g/g and 0.296 g/g with 96% ILs recovery. The study showed the potential of ILs pretreatment for lignin removal of the corncob under alkaline condition which may be applicable to other lignocellulosic materials. [Display omitted] • Ionic liquid under alkaline condition selectively dissolves the lignin upto 68%. • Crystallinity of biomass was reduced from 62% to 29%. • Addition of ammonia has no effect on chemical nature of ionic liquids. • About 96% of ionic liquid were recyclable with less than 4% of efficiency loss. • Maximum hydrolysability of 91% and fermentability of 86% was observed. [ABSTRACT FROM AUTHOR]

In this study, it was found that soluble polysaccharides (SPs) from rice straw were conjugated with high levels of phenolic compounds. A gradient ethanol precipitation method was used to separate conjugates with different phenolic compound components. These conjugates were mainly composed of disaccharides or trisaccharides and phenolic acids that were mainly p- coumaric acid, ferulic acid, vanillic acid, and vanillin. SPs with more conjugates exhibited better effects on Saccharomyces cerevisiae and ethanol fermentation. The change in the proportion of conjugates in SPs significantly affected the accumulation of intracellular trehalose and glycerol content, indicating the effect of the conjugates on intracellular osmotic stress. Moreover, SPs with more conjugates generated lower intracellular hydrogen peroxide (H 2 O 2) levels. Thus, oligosaccharide and phenolic compound conjugates in SPs promoted yeast growth and ethanol fermentation. For instance, OD value reached 9.4, which was 1.3 times higher than the control group, and ethanol content at 36 h was 36.5 g/L, which was 1.3 times higher than the control. Osmotic pressure alleviation and lowered intracellular H 2 O 2 levels by conjugates are key mechanisms of the SPs during yeast growth and ethanol fermentation. [Display omitted] • SPs from rice straw contained oligosaccharide-phenolic compound conjugates. • The conjugates were mainly composed of disaccharides and phenolic acid. • The conjugates significantly affected SPs to alleviate osmotic stress. • The conjugates could lower intracellular H 2 O 2 levels during ethanol fermentation. [ABSTRACT FROM AUTHOR]

To reuse organic acids in wastewater, efficient acetone-butanol-ethanol (ABE) fermentation was constructed using mixed acetic acid and lactic acid. The mixed acids were co-consumed with glucose, producing higher butanol concentration (6.96 g/L) and butanol yield (0.494 C-mol/C-mol) than using each single acid (6.22 g/L and 0.432 C-mol/C-mol). This result was verified by 13C tracer experiment that addition of lactic acid improved carbon distribution to butanol instead of acetone, while acetic acid was readily consumed than lactic acid at initial fermentation stage. Subsequently, pH-stat fed batch fermentation at low pH of 5.5 further improved acid consumptions (6.34 g/L acetic acid and 9.06 g/L lactic acid) and solvent productions (12.4 g/L butanol and 6.50 g/L acetone). Finally, ABE fermentation using wastewater of lactic acid fermentation was performed without inhibition. Thus, efficient ABE fermentation can be implemented using mixed acetic acid and lactic acid, which is superior to using single acid. • This is the first study using mixed acetate and lactate for ABE fermentation. • 13C experiment verified the metabolic flux to butanol was improved by the acids. • pH and glucose played an important role in acid consumption and solvent production. • Fermentation from lactic acid fermentation broth was performed without inhibition. [ABSTRACT FROM AUTHOR]

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]

Harnessing the ability of microorganisms to fix, convert and utilize CO 2 for chemical production has important implications for global carbon reduction. In this study, carbonic anhydrase (CA) and/or phosphoenolpyruvate carboxykinase (PEPCK) were overexpressed in Corynebacterium acetoacidophilum. A process was established to capture CO 2 and convert it into succinic acid (SA) from the off-gas produced by Saccharomyces cerevisiae fermenting ethanol (EtOH), using the engineered strain of C. acetoacidophilum. By constructing a coupling device and optimizing the ratio of working medium volumes in the two-chamber bioreactor, the maximum yields of EtOH and SA from glucose were 0.51 g/g and 0.70 g/g, respectively. A scale-up trial was performed in a 3-L fermenter and calculation of the environmental factors demonstrated that the linked-fermentation strategy was more environmentally-friendly than conventional SA fermentation, indicating potential for industrial application. [Display omitted] • Engineered C. acetoacidophilum with strong CO 2 fixation ability was constructed. • The engineered C. acetoacidophilum captured the CO 2 from ethanol fermentation. • The maximum conversion rate of SA from glucose was 0.70 g/g in co-fermentation. • The E-factor of co-fermentation showed a more environmentally friendly process. [ABSTRACT FROM AUTHOR]

The fermented beverage industry is always pursuing alternatives to make products that delight consumers with special or unique characteristics. The identification and improvement of new yeast strains emerge as an opportunity; however, wild strains usually have a limitation in maltose fermentation and/or off-flavors production. Here we report the production of a Blond-style ale beer using a bioethanol isolated strain (LBGA-287) with flavor complexity approved in sensorial panels. LBGA-287 also showed an increase in maltose consumption, growth and fermentation rates when compared to the commercial yeast. Using qPCR analysis, genes related to the (i) efficiency of fermentation (ii) production of aromas/off-flavors, and (iii) metabolization of carbohydrates were found as differentially expressed in the isolated strains when compared to industrial yeast. This suggests that LBGA-287 could have an important impact on beer production, improving brewing efficiency, quality and diversity of this beverage, and most importantly satisfying the final consumer. Screening of 289 yeasts isolated from Brazilian ethanol production was used to select a Saccharomyces cerevisiae strain suitable for beer production. A total of 47 potential strains were evaluated for growth and maltose consumption. Two of them were compared to the industrial yeast S-04 regarding gene expression related to fermentation efficiency, production of aroma, and resistance to stress. They were also used to produce a Belgian blond ale beer. The sensory evaluation indicated that the beer produced using LBGA-287 was well accepted, showing this strain's suitability for brewery use. [Display omitted] • A yeast strain isolated from Brazilian ethanol production was used to produce beer. • The beer produced with LBGA-287 was approved by specialists and general public. • Gene expression pattern was different from the industrial strain. • Genes involved in the consumption of fermentable sugars were upregulated. • LBGA-287 had a fine regulation of genes involved in production of volatiles. [ABSTRACT FROM AUTHOR]

• ABA accelerated postharvest ripening of nanguo pears, whereas NDGA delayed it. • Ethanol fermentation was promoted by ABA while inhibited by NDGA during ripening. • ABA had a promoting effect on glycolysis while NDGA had the opposite effect. • The TCA cycle in Nanguo pears was modulated by ABA during ripening. • Expression of PDC and ADH was differentially regulated by ABA during ripening. The aim of this study was to explore the role of abscisic acid (ABA) in ethanol fermentation during postharvest ripening of Nanguo pear fruit (Pyrus ussuriensis Maxim.). Pears harvest at commercial maturity were treated with 100 μmol L−1 ABA or its biosynthesis inhibitor nordihydroguaiaretic acid (NDGA). Our data indicated that ABA treatment promoted respiration rate and ethylene production during ripening compared with controls, while NDGA treatment had the opposite effects. During the early ripening stage, flesh firmness in ABA treatment group was lower than in controls; while in NDGA treatment group, it was higher than in controls. The contents of glucose, ethanol and acetaldehyde were increased by ABA treatment while reduced by NDGA treatment during ripening compared with the controls. ABA treatment promoted pyruvate and acetyl-CoA contents, whereas application of NDGA reduced pyruvate content and delayed the peak of acetyl-CoA content compared with the controls. The oxaloacetic acid (OA) and citric acid (CA) contents were reduced by ABA treatment while increased by NDGA treatment during ripening. ABA treatment promoted pyruvate decarboxylase (PDC) and alcohol dehydrogenase (ADH) activities, whereas NDGA treatment reduced their activities mainly at the early ripening stage. Quantitative real-time polymerase chain reaction (qPCR) showed that expression of PDC1, ADH1 and ADH2 was differentially up-regulated by ABA treatment during ripening while down-regulated by NDGA treatment compared with the controls. PDC2 expression was enhanced after application of NDGA during ripening while reduced by ABA treatment at the early ripening stage. Our data indicated that ABA had a promoting effect on ethanol fermentation during ripening of Nanguo pear fruit. [ABSTRACT FROM AUTHOR]

• Cooling water consumption has been reduced up to 62.1%. • Extractive fermentation with CO 2 could enhance the process in warm regions. • The fermentation was carried out at the ideal temperature of the yeast (34 °C). • Specific gas flow rate and substrate concentration were evaluated in the simulations. • Extractive fermentation with CO 2 allowed keeping the optimum fermentation temperature. Ethanol production from sugarcane is an exothermic process. The heat generated during the fermentation is removed by heat exchangers, using cooling water. However, it is difficult to keep the fermentation process close to the optimum yeast temperature, especially in hot months. In this work, extractive fermentation with CO 2 stripping was evaluated as a way to overcome this operational problem besides reducing the water demand in the process. A mathematical model was developed to describe conventional and extractive fed-batch ethanol fermentation processes. Simulations were performed to determine the effect of different gas flow rates on heat removal from fermentations at different must substrate concentrations (C s m). With a C s m of 285.7 g/L and a CO 2 flow rate of 0.7 vvm, the consumption of cooling water in the extractive fermentation decreased by up to 62.1% compared to the conventional process, keeping the broth temperature constant. Thus, the potential of this technique to increase the total ethanol content and reduce the cooling water consumption was demonstrated. Furthermore, there were decreases in the amount of vinasse and steam consumption in the distillation step. [Display omitted] [ABSTRACT FROM AUTHOR]

• Kinetic modeling of ethanol fermentation in biofilm reactor with non-sterile/(un)enriched media. • Sensitivity analysis by increasing or decreasing each parameter of the developed models by 5% • Techno-economic feasibility of ethanol fermentation in biofilm reactor was detected. • Growth-associated ethanol production processes were revealed in the biofilm reactor. • Ethanol production from NSUE medium was more economical than that of the NSE medium. This study aimed to model kinetically ethanol fermentation by Saccharomyces cerevisiae in the biofilm reactor, analyze the sensitivity of the developed model, and determine the techno-economic feasibility of ethanol fermentation. Two different media including the non-sterile enriched (NSE) and non-sterile unenriched media (NSUE) were evaluated for ethanol production. Based on the results, the experimental biomass production, ethanol production, and substrate consumption data from both the NSE and NSUE media were fitted very well by the logistic, Luedeking-Piret, and modified Luedeking-Piret models developed for each fermentation with higher R2 values than 0.96. Besides, it was determined that the ethanol production processes were growth-associated as α values (g ethanol/g substrate) were higher than β values (g ethanol/g substrate/h). Sensitivity analysis gave extremely satisfactory results with high R2 values ranging from 0.960 to 0.995. According to the techno-economic analysis, ethanol production from the NSUE medium was more economical than that of the NSE medium since its economic yield and economic productivity values were 21.0–21.1 and 13.4–16.8 times higher, respectively. Consequently, the developed models estimated successfully the experimental data yielded from non-sterile (un)enriched media in the biofilm reactor and can be used to describe ethanol fermentation under non-sterile conditions. [ABSTRACT FROM AUTHOR]

[Display omitted] • Detailed analysis on gas transfer rate in industrial syngas fermentation. • CFD reveals mass transfer limitation topography in external-loop gas-lift reactors. • Bubbles smaller than 2 mm are key to reach required mass transfer capacities. • The produced ethanol minimizes bubble size and increases gas hold-up. • Transport limitations in air–water systems can be alleviated in syngas fermentation. Mass transfer limitations in syngas fermentation processes are mostly attributed to poor solubility of CO and H 2 in water. Despite these assumed limitations, a syngas fermentation process has recently been commercialized. Using large-sale external-loop gas-lift reactors (EL-GLR), CO-rich off-gases are converted into ethanol, with high mass transfer performance (7–8.5 g.L-1.h−1). However, when applying established mass transfer correlations, a much poorer performance is predicted (0.3–2.7 g.L-1.h−1). We developed a CFD model, validated on pilot-scale data, to provide detailed insights on hydrodynamics and mass transfer in a large-scale EL-GLR. As produced ethanol could increase gas hold-up (+30%) and decrease the bubble diameter (≤2 mm) compared to air–water mixtures, we found with our model that a high volumetric mass transfer coefficient (650–750 h−1) and mass transfer capacity (7.5–8 g.L-1.h−1) for CO are feasible. Thus, the typical mass transfer limitations encountered in air–water systems can be alleviated in the syngas-to-ethanol fermentation process. [ABSTRACT FROM AUTHOR]