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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]

The medium composition and fermentation parameters play a critical role in the fermentation process. Therefore, in the present study, the effects of fermentation parameters (initial glucose concentration (IGC), inoculation ratio (IR), initial pH value (IPV), stirring rate (SR), and temperature (T)) and medium composition (yeast extract (YE) and peptone (PEP)) on bioethanol production from glucose by using Scheffersomyces stipitis in shake flask fermentation were studied, respectively. According to results, the highest ethanol yield (YP/S) was achieved to be 47.63% when IGC, IR, IPV, SR, T, and nitrogen concentrations were 15 g/L, 5% (v/v), 5.5, 150 rpm, 30 °C, 5 g/L YE, and 20 g/L PEP, respectively. Nevertheless, the best fermentation parameters were 15 g/L IGC, 5% (v/v) IR, 5.5 IPV, 150 rpm SR, 30 °C T, no YE, and 5 g/L of PEP, respectively. At these conditions, kinetic results including bioethanol production, YP/S, ethanol yield per biomass, maximum production rate, sugar utilization yield, and theoretical YP/S were 8.29 g/L, 47.26%, 5.08 g ethanol/g biomass, 0.41 g/L/h, 95.86%, and 92.49%, respectively. In conclusion, these results indicated that although the concentrations of ingredients (YE and PEP) used in the fermentation medium were considerably decreased from 10 and 20 g/L to 0 and 5 g/L, the kinetic results of the fermentation were preserved compared to the initial fermentation studies. Nevertheless, further improvement of the determined fermentation parameters could be performed in the bioreactor. [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]

One of the challenges in biofuel production from lignocellulosic wastes is to improve its conversion to solvents; therefore, new strategies to enhance xylose uptake are required due to be the secondary abundant sugar. In this context, a novel fermentation strategy integrating a co-culture of Clostridium acetobutylicum and Saccharomyces cerevisiae with pH control was developed. Initially, two different buffers, ammonium acetate and calcium carbonate, were tested under pHmin > 4.8 by fermenting 60 g L−1 of glucose with the C. acetobutylicum monoculture. Ammonium acetate was selected for fermenting media as butanol production was increased from 9.8 to 10.9 g L−1 over the calcium carbonate test. Comparing with the spontaneous acetone-butanol-ethanol (ABE) fermentation with C. acetobutylicum when no xylose consumption was observed, xylose consumption was efficiently increased by controlling pHmin > 4.8. The xylose consumption was > 47% either by using a 45:15 g L−1 glucose:xylose mixture or with rice straw (RS) hydrolysate. Clostridium monoculture using RS hydrolysate and pHmin > 4.8 produced a butanol (ABE) concentration of 6.5 (9.5) g L−1. While it increased to 7.0 (13.1) g L−1 when the co-culture with S. cerevisiae was used using same pH regulation strategy mainly due to ethanol increase up to 2.7 g L−1. Moreover, the xylose uptake doubled to 94% due to amino-acid secretion by yeast. Overall, this combined strategy was a very effective method for promoting sugar consumption and ABE solvent production from lignocellulosic waste. [ABSTRACT FROM AUTHOR]

The complex structure of rice straw is such that its bioconversion requires multiple physical and chemical pretreatment steps. In this study, it was found that a large amount of soluble polysaccharides (SPs) are formed during the pretreatment of straw. The yield of NaOH-based SPs (4.8%) was much larger than that of ball-milled SPs (1.5%) and H2SO4-based SPs (1.1%). For all the pretreatments, the ratio of phenolic compounds to saccharides (P/S) for each type of SPs increased upon increasing the concentration of ethanol in the order of 90% > 70% > 50%. The yield of NaOH-based SPs was much higher than that of acid-based and ball-milled SPs. The changes in the 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid (ABTS), ferric reducing antioxidant power assay (FRAP), and 2,2-diphenyl-1-picrylhydrazyl (DPPH) of SPs follow the same rule, i.e., the higher the P/S ratio, the higher the antioxidant values of the SPs. The flow cytometry and laser scanning microscopy results show that the P/S ratio can significantly influence the effect of SPs on microbial growth and cell membrane permeability. Upon varying the ethanol concentration in the range of 50–90%, the P/S ratio increased from 0.02 to 0.17, resulting in an increase in the promoting effects of the SPs on yeast cell growth. Furthermore, H2O2, NAD+/NADH, and NADP+/NADPH assays indicate that SPs with a high P/S ratio can reduce intracellular H2O2 and change the intracellular redox status. [ABSTRACT FROM AUTHOR]

Eucheuma denticulatum is a red macroalgae with a high carbohydrate content. The fermentable sugars from E. denticulatum were obtained through sequential thermal acid hydrolysis, enzymatic saccharification, and detoxification. Thermal acid hydrolysis of E. denticulatum was optimized under the condition of 10% (w/v) slurry content and 300 mM HNO3 at 121 ℃ for 90 min. The maximum monosaccharide concentration after thermal acid hydrolysis was 31.0 g/L with an efficiency (ETAH) of 44.7%. By further enzymatic hydrolysis of pretreated biomass solution under 20 U/mL Cellic CTec2 at 50 ℃ and 160 rpm for 72 h, the maximum monosaccharide concentration reached 79.9 g/L with an efficiency of 66.2% (ES). To remove 5-hydroxymethylfurfural (5-HMF), a fermentation inhibitor, absorption using 2% activated carbon was performed for 2 min. Ethanol fermentation was performed using wild-type and high galactose-adapted strains of Saccharomyces cerevisiae, Kluyveromyces marxianus, and Candida lusitaniae. As a result, galactose-adapted strains showed higher ethanol production than wild-type strains. Especially, the fermentation result by adaptively evolved S. cerevisiae produced the highest ethanol of 37.6 g/L and with YEtOH of 0.48 g/g. Moreover, the transcript level of MIG1 in the galactose-adapted strain was slightly lower than that in the wild-type strain. The application of adaptive evolution of microorganisms was efficient for bioethanol production. [ABSTRACT FROM AUTHOR]

The soluble and fermentable carbohydrate contents was detected over 47% of glucose and fructose in Chinese Elaeagnus angustifolia fruit powder (EAF), being over 47 wt% sugar content more than that of grape. Ethanol was therefore fermented directly from EAF, and different submerged fermentation modes were comparatively employed to optimize ethanol harvest. The results indicated that glucose has certain competitive inhibition on fructose bio-utilization, as well as the EAF solid residue involved fermentation mode also hindered the fermented-ethanol titer. Pectinase addition and in situ hydrolysis seemed to assist somewhat the fermentation. The water-solute fermentation mode is preferable, and glucose and fructose components were completely consumed and converted to 80.96 g/L ethanol at 87.6% ethanol yield even under tannin and pectin inhibition. The fermentation result could provide some experimental data and an approach to not only new biomass resource explores of bioethanol and alcohol beverage production, but also the technological development on valorization commercials of EAF in global draught areas. [ABSTRACT FROM AUTHOR]

Direct reutilization of condensate can inhibit ethanol fermentation, 2-phenylethyl alcohol and furfural existed in the condensate are considered to be inhibitors. To achieve the reutilization of the condensate, the ozonation combined with ion-exchange method was used. The results showed that the elimination rates of 2-phenylethyl alcohol and furfural reached 98.0% and 100.0%, respectively after ozonation, while the concentrations of acetic acid, propionic acid, butyric acid and valeric acid increased by 14.9%, 7.7%, 35.3% and 25.5%, respectively. The fermentation results showed that the inhibition of the condensate after ozonation was alleviated but was not completely eliminated. When the effluent volume treated by the ion-exchange method reached 80 BV, the concentrations of acetic acid, propionic acid, butyric acid and valeric acid decreased by 25.8%, 8.6%, 6.5% and 34.4%, respectively. The fermentation results showed that the inhibition of the condensate was completely eliminated after ozonation combined with ion-exchange treatment. [ABSTRACT FROM AUTHOR]

In this study, various mathematical functions were utilized to fit the observed values and the kinetic parameters of fermentation in immobilized-cell stirred tank reactor (ICSTR) with carob extract medium (CEM). The best model was selected based on the residual sum of squares (RSS), root-mean-square-error (RMSE), mean-absolute-error (MAE), determination coefficient (R2), slope (m), bias factor (BF), accuracy factor (AF), the objective function (Φ-factor), and f-testing. Therefore, the Stannard (ST) model was good agreement with the actual biomass production (X), ethanol production (P), and sugar consumption (S) data (RSS = 0.22, 6.23, and 45.70 g/L; RMSE = 0.17, 0.88, and 2.39 g/L; MAE = 0.14, 0.64, and 1.72 g/L; R2 = 0.9948, 0.9977, and 0.9972; m = 1.03, 1.02, and 1.02; BF = 1.35, 1.08, and 0.97; AF = 1.41, 1.14, and 1.04; and Φ-factor = 0.008, 0.004, and 0.005 (∑Φ-factor = 0.017) for X, P, and S, respectively). In the prediction of kinetic parameters belonging to the experimental fermentation, the ST model also gave better, satisfactory, and well-directed results than the other mathematical models. Besides, the ST model was also accomplishedly validated using two independent sets of the experimental data yielded from the different carbon sources in various concentrations. Consequently, the models proposed for X, P, and S can serve as universal functions to predict the real values and the kinetic parameters of the ethanol fermentation. Besides, these models can be applied to improve the ethanol fermentation in the ICSTR with CEM. [ABSTRACT FROM AUTHOR]

Kinases modulate the various physiological activities of microbial fermenting strains including the conversion of lignocellulose-derived phenolic aldehydes (4-hydroxyaldehyde, vanillin, and syringaldehyde). Here, we comprehensively investigated the gene transcriptional profiling of the kinases under the stress of phenolic aldehydes for ethanologenic Zymomonas mobilis using DNA microarray. Among 47 kinase genes, three genes of ZMO0003 (adenylylsulfate kinase), ZMO1162 (histidine kinase), and ZMO1391 (diacylglycerol kinase), were differentially expressed against 4-hydroxybenzaldehyde and vanillin, in which the overexpression of ZMO1162 promoted the phenolic aldehydes conversion and ethanol fermentability. The perturbance originated from plasmid-based expression of ZMO1162 gene contributed to a unique expression profiling of genome-encoding genes under all three phenolic aldehydes stress. Differentially expressed ribosome genes were predicted as one of the main contributors to phenolic aldehydes conversion and thus finally enhanced ethanol fermentability for Z. mobilis ZM4. The results provided an insight into the kinases on regulation of phenolic aldehydes conversion and ethanol fermentability for Z. mobilis ZM4, as well as the target object for rational design of robust biorefinery strains. [ABSTRACT FROM AUTHOR]

This study proposed a recyclable p-toluenesulfonic acid (p-TsOH) fractionation process for co-producing lignin nanoparticles (LNPs) and fermentable sugars from lignocellulosic biorefinery biowaste (enzymatic hydrolysis residue (EHR)). The prepared LNPs were used to detoxify the inhibitors in the xylose-rich prehydrolyzate for improving ethanol production. Results showed that the EHR was fractionated into a cellulose-rich water-insoluble solid (WIS) fraction and a lignin-rich spent liquor (SL) fraction. Cellulase hydrolysis of WIS produced 97.7% of glucose yield, while the LNPs of an average particle size of 98.0 nm with 76.3 % yield (based on the untreated EHR) were obtained from the diluted SL. LNPs demonstrated higher detoxification ability than EHR at the same dosage. Moreover, the fermentability of the detoxified xylose-rich prehydrolyzate was significantly improved. The sugar utilization ratio was 94.8%, and the ethanol yield reached its peak value of 85.4% after 36 h of fermenting the detoxified xylose-rich prehydrolyzate. [ABSTRACT FROM AUTHOR]

NADH-dependent reductase enzyme catalyzes the phenolic aldehyde conversion and correspondingly improves the ethanol fermentability of the ethanologenic Zymomonas mobilis. This study constructed the transcriptional landscape of mono/dioxygenase genes in Z. mobilis ZM4 under the stress of the toxic phenolic aldehyde inhibitors of 4-hydroxybenzaldehyde, syringaldehyde, and vanillin. One specific dioxygenase encoding gene ZMO1721 was differentially expressed by 3.07-folds under the stress of 4-hydroxybenzaldehyde among the eleven mono/dioxygenase genes. The purified ZMO1721 shared 99.9% confidence and 48.0% identity with the oxidoreductase in Rhodoferax ferrireducens T118 was assayed and the NADH-dependent reduction activity was confirmed for phenolic aldehyde vanillin conversion. The ZMO1721 gene was then overexpressed in Z. mobilis ZM4 and the 4-hydroxybenzaldehyde conversion rate was accelerated. The cell growth, glucose consumption, and ethanol productivity of Z. mobilis ZM4 were also improved by ZMO1721 overexpression. The genes identified on improving phenolic aldehyde tolerance and ethanol fermentability in this study could be used as the synthetic biology tools for modification of ethanologenic strains. [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]

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]

Direct hydrolysis of a towel to glucose was investigated using microwave-assisted (MW) treatment combined with impregnation in concentrated sulfuric acid (SA) solution (51 wt% for 30 min) before the MW treatment. The maximum glucose yield by direct hydrolysis of an untreated towel was 30.9%, obtained at a heating temperature of 200 °C for 2 min. The maximum total glucose yield (from both direct hydrolysis and enzymatic hydrolysis of treated residue) was 74.2%, attained at a microwave heating temperature of 180 °C for 3 min. This condition is milder than that of MW treatment without impregnation in concentrated SA (our previous study, heating temperature of 200 °C for 7 min required). As shown by XRD of the unimpregnated and impregnated towels (in 9 and 36 wt% SA solution), the crystallinity index value decreased with the increase in SA concentration. Finally, 22.4 g of ethanol could be produced using the supernatant (containing glucose) and the microwave-treated residue as a carbon source for Saccharomyces cerevisiae, with less fermentation inhibition. Thus, impregnation in concentrated SA before MW treatment is effective for the production of glucose from cellulosic material and has low energy input. [ABSTRACT FROM AUTHOR]

Biofuel research and development roadmap is currently underway in several countries and is expected to pave a way for the establishment of a viable renewable energy sector that can compete with petroleum-based fuels. Ethanol fermentation has garnered increasing attention amongst various stakeholders (industries, governments, and academia) due to its economic and environmental merits. However, microbial contamination continues to be one of the major barriers in ethanologenic processes, resulting in low ethanol yields and thereby translating into economic losses. To this end, technological innovations geared towards effective elimination of microbial contamination are constantly being developed. This review explores and discusses the fermentation conditions that facilitate the growth of undesired microorganisms during ethanol fermentation processes. It highlights the methods that are currently used in biorefineries as well as innovative and advanced biotechnological methods currently being evaluated as viable alternative strategies to control or eliminate microbial contaminants in ethanol fermentations. These methods have the potential to minimize or control the contamination problem and could pave a way for the development of an efficient biofuel sector. [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]

A thermotolerant ethanol fermenting yeast strain is a key requirement for effective ethanol production at high temperature. This work aimed to select a thermotolerant yeast producing a high ethanol concentration from molasses and increasing its ethanol production by mutagenesis. Saccharomyces cerevisiae DMKU 3-S087 was selected from 168 ethanol producing strains because it produced the highest ethanol concentration from molasses at 40 °C. Optimization of molasses broth composition was performed by the response surface method using Box–Behnken design. In molasses broth containing optimal total fermentable sugars (TFS) of 200 g/L and optimal (NH4)2SO4 of 1 g/L, with an initial pH of 5.5 by shaking flask cultivation at 40 °C ethanol, productivity and yield were 58.4 ± 0.24 g/L, 1.39 g/L/h and 0.29 g/g, respectively. Batch fermentation in a 5 L stirred-tank fermenter with 3 L optimized molasses broth adjusted to an initial pH of 5.5 and fermentation controlled at 40 °C and 300 rpm agitation resulted in 72.4 g/L ethanol, 1.21 g/L/h productivity and 0.36 g/g yield at 60 h. Strain DMKU 3-S087 improvement was performed by mutagenesis using ultraviolet radiation and ethyl methane sulfonate (EMS). Six EMS mutants produced higher ethanol (65.2 ± 0.48–73.0 ± 0.54 g/L) in molasses broth containing 200 g/L TFS and 1 g/L (NH4)2SO4 by shake flask fermentation at 37 °C than the wild type (59.8 ± 0.25 g/L). Among these mutants, only mutant S087E100-265 produced higher ethanol (62.5 ± 0.26 g/L) than the wild type (59.5 ± 0.02 g/L) at 40 °C. In addition, mutant S087E100-265 showed better tolerance to high sugar concentration, furfural, hydroxymethylfurfural and acetic acid than the wild type. [ABSTRACT FROM AUTHOR]

In order to improve the slow ethanol fermentation during acetic acid fermentation process of black raspberry vinegar (BRV), the microbiological and physicochemical aspects of the effects of indigenous Saccharomyces cerevisiae JBCC-21A were examined. The selected S. cerevisiae JBCC-21A showed better growth and ethanol production rates than the commercial yeast strains. The ethanol production rate was 3-times faster than the traditional method. Acetic acid fermentation by S. cerevisiae JBCC-21A began 10 days earlier than the traditional method and reached up to 60 g/L acetic acid. Bacterial counts revealed Acetobacter pasteurianus was the only dominant species throughout the inoculated acetic acid fermentation. The physicochemical and functional properties of the fermented vinegar using indigenous S. cerevisiae JBCC-21A maintained a high quality similar to the traditional method, while being the faster fermentation process. Thus, it is suggested that inoculation of the indigenous S. cerevisiae strain in order to shorten the fermentation time without affecting the quality of traditional BRV. [ABSTRACT FROM AUTHOR]

Environmental and energy concerns have increased interest in renewable energy sources, particularly biofuels. Thus the fermentation of glucose from sulfuric acid-hydrolyzed corn stover for the production of bioethanol has been explored using a combined acid retardation and continuous-effect membrane distillation treatment process. This process resulted in the separation of the sugars and acids from the acid-catalyzed hydrolysate, the removal of most of the fermentation inhibitors from the hydrolysate and the concentration of the detoxified hydrolysate. The recovery rate of glucose from the sugar-acid mixture using acid retardation was greater than 99.12% and the sulfuric acid was completely recovered from the hydrolysate. When the treated corn stover hydrolysate, containing 100 g/L glucose, was used as a carbon source, 43.06 g/L of ethanol was produced with a productivity of 1.79 g/(L∙h) and a yield of 86.31%. In the control experiment, where glucose was used as the carbon source these values were 1.97 g/(L∙h) and 93.10% respectively. Thus the integration of acid retardation and a continuous-effect membrane distillation process are effective for the production of fuel ethanol from corn stover. [ABSTRACT FROM AUTHOR]

In this study, the effectiveness of the ethanol fermentation pretreatment for biomethanation was examined. A sequential batch biomethanation experiment was performed for 130 days using artificial food waste, which was saccharized and ethanol fermented without any evaporation of ethanol. This is compared with a control experiment without pretreatment. Methane yields of the control and pretreatment series were 420 and 460 mL/g of the added volatile solids (VS) with 53% and 68% of methane content, 0.082 and 0.014 g of volatile suspended solids/g VS added for sludge yield, and 87% and 94% for VS biodegradability, respectively. In terms of material balance, the generation of carbon dioxide during biomethanation from an ethanol fermented substrate is lower in volume than that without it, because carbon dioxide is released during ethanol fermentation. The lower sludge generation of the ethanol fermented substrate results from the biomass yield of ethanol and free energy obtained from the biomethanation of ethanol, which is lower than that obtained from the biomethanation of starch. [ABSTRACT FROM AUTHOR]

Direct hydrolysis of a towel to glucose was investigated using steam explosion and microwave-assisted treatment to find effective uses for cotton waste. The maximum glucose yield by direct hydrolysis (based on an untreated towel) was 18.8%, obtained at a steam pressure of 5.5 MPa (at 271 °C) and steaming time of 5 min using steam explosion. For the microwave-assisted treatment, with a 1.0 (w/w)% sulfuric acid catalyst, the maximum glucose yield by direct hydrolysis was 28.9%, obtained at a microwave heating temperature of 200 °C for 7 min. The maximum total glucose yield (from both direct hydrolysis and enzymatic hydrolysis of treated residue) was 78.0%, attained at a microwave heating temperature of 200 °C for 7 min with 0.5 (w/w)% sulfuric acid catalyst. Furthermore, the maximum total glucose and valuable water soluble chemicals (cellobiose, 5-hydroxymethylfurfural, formic acid, and levulinic acid), 94.1%, were achieved at heating temperature of 200 °C for 10 min with 0.5 (w/w)% sulfuric acid catalyst. Finally, ethanol, 84.5% of conversion rate, could be produced using supernatant (it contained glucose) and microwave treated residue (200 °C for 7 min with 0.25 (w/w)% sulfuric acid catalyst) as carbon source for Saccharomyces cerevisiae with less fermentation inhibition. [ABSTRACT FROM AUTHOR]

The development of sustainable bioethanol fuel production from food waste has increasingly become an attractive topic. Food waste is recognized as the most available and costless feedstock. Therefore, ethanol production has been adopted as cost-efficient and an ecological way for FW disposal. This paper reviewed the microorganisms utilized for ethanol fermentation, the effect of enzymatic hydrolysis on ethanol concentration, optimization of accurate process parameters, and recycling of huge volumes of stillage for ethanol production towards reducing any incurred environmental burdens and minimizing the cost. The statistical tools which may enhance the process efficiency had been presented. Also, the perspective and the future development were introduced. All these aimed to fully utilize the food waste and also reduce the cost for side-product in this process; proper operation conditions and the control methods for stillage recycling were considered as the methods to improve ethanol fermentation from food waste. [ABSTRACT FROM AUTHOR]

Renewable resources are the most abundant available and inexpensive materials on the earth. This study was undertaken not only to optimize acid pretreatment conditions of rice straw but also to produce ethanol from the detoxified rice straw hydrolysate (RSH) by the yeasts Saccharomyces cerevisiae and Scheffersomyces stipitis. Box-Behnken response surface design was used to determine optimum temperature (105-135 °C), dilute sulfuric acid ratio (1-5%, w/v), and solid-to-liquid ratio (1:19-1:15, w/v). Results indicated that the optimum hydrolysis conditions of rice straw were 126.5 °C, 1:15 solid-to-liquid ratio (w/v) and 5% acid ratio (w/v). Reducing sugar concentration (RSC) was 21.50 g/L (0.323 g sugar/g biomass) under optimal conditions. After detoxification process with activated charcoal, the percentage removal of acetic acid, hydroxymethyl furfural, 2-furaldehyde, and phenolics was 2.01, 78.58, 100, and 94.67%, respectively. The catalytic efficiency of sulfuric acid was achieved to be 3.40 and 5.33 g/g in non-detoxified and detoxified RSHs, respectively. The ethanol yields and maximum production rates for S. cerevisiae and S. stipitis (ATCC 58784 and ATCC 58785) were calculated as 47.20% of theoretical ethanol yield and 0.37 g/L/h, 42.95% of theoretical ethanol yield and 0.09 g/L/h, and 48.81% of theoretical ethanol yield and 0.07 g/L/h, respectively. Consequently, rice straw can be a good substrate source for production of value-added products such as ethanol by fermentation. Besides, in the case of further improvement of fermentation media in terms of inhibitors, especially of acetic acid, better fermentation results would be obtained. [ABSTRACT FROM AUTHOR]

Wine fermentations using rice media containing either Monascus koji or rice nuruk were performed and fermentative characteristics based on the koji type were investigated. Cultivations were performed in a 20 °C room in a 20 L bottle with the rice media that included Monascus rice koji at both 20 and 30%, or rice nuruk at 20%. After 22 days of cultivation, the ethanol yield reached 14.2-14.6% (v/v) for M. koji and 16.5% (v/v) for rice nuruk. This lower yield with use of M. koji was thought to be due to rapid cell concentration decreases in the later stage. Total amounts of organic acids and volatile compounds in fermentations using M. koji were 166-172 and 1779-1874 mg/L, respectively, being 8.7-12.9% and 46.3-54.1% higher than with use of rice nuruk. With M. koji, a high quality rice wine was produced with high levels of volatile compounds and monacolin K. [ABSTRACT FROM AUTHOR]

In this work, the effect of initial sugar concentration and temperature on the production of ethanol by Saccharomyces cerevisiae CCA008, a flocculent yeast, using cashew apple juice in a 1L-bioreactor was studied. The experimental results were used to develop a kinetic model relating biomass, ethanol production and total reducing sugar consumption. Monod, Andrews, Levenspiel and Ghose and Tyagi models were investigated to represent the specific growth rate without inhibition, with inhibition by substrate and with inhibition by product, respectively. Model validation was performed using a new set of experimental data obtained at 34 °C and using 100 g L of initial substrate concentration. The model proposed by Ghose and Tyagi was able to accurately describe the dynamics of ethanol production by S. cerevisiae CCA008 growing on cashew apple juice, containing an initial reducing sugar concentration ranging from 70 to 170 g L and temperature, from 26 to 42 °C. The model optimization was also accomplished based on the following parameters: percentage volume of ethanol per volume of solution (% V / V ), efficiency and reaction productivity. The optimal operational conditions were determined using response surface graphs constructed with simulated data, reaching an efficiency and a productivity of 93.5% and 5.45 g L h, respectively. [ABSTRACT FROM AUTHOR]

A strategy for monitoring fermentation processes, specifically, simultaneous saccharification and fermentation (SSF) of corn mash, was developed. The strategy covered the development and use of first principles, semimechanistic and unstructured process model based on major kinetic phenomena, along with mass and energy balances. The model was then used as a reference model within an identification procedure capable of running on-line. The on-line identification procedure consists on updating the reference model through the estimation of corrective parameters for certain reaction rates using the most recent process measurements. The strategy makes use of standard laboratory measurements for sugars quantification and in situ temperature and liquid level data. The model, along with the on-line identification procedure, has been tested against real industrial data and have been able to accurately predict the main variables of operational interest, i.e., state variables and its dynamics, and key process indicators. The results demonstrate that the strategy is capable of monitoring, in real time, this complex industrial biomass fermentation. This new tool provides a great support for decision-making and opens a new range of opportunities for industrial optimization. [ABSTRACT FROM AUTHOR]

Lignocellulosic materials have been considered low-cost effective substrates for bioethanol production. However, lignocellulosic pretreatment releases toxic compounds such as 5-hydroxymethylfurfural (HMF) that is known to inhibit the yeast growth and ethanol production. In this work, flow cytometry was used to monitor the physiological response of the yeast Saccharomyces carlsbergensis ATCC 6269 in the presence of different initial HMF concentrations within the range of 0-15 g/L, in terms of cell membrane integrity, potential, and intracellular lipids. It was observed that the HMF presence affected more significantly the yeast growth than the ethanol production. At 15 g/L HMF, the yeast growth and fermentation ability were completely inhibited. The cell membrane integrity and potential decreased as the initial HMF concentration increased. At the end of the fermentation process with 10 g/L HMF, the yeast culture contained 45 % of cells with depolarized plasma membrane, 52 % of cells with permeabilized plasma membrane, and 53 % of cells with increasing reactive oxygen species (ROS) levels. Using the Nile Red stain, it was observed that intracellular polar lipids were more affected by the initial HMF concentration than the neutral lipids, probably due to the extensive membrane damage. [ABSTRACT FROM AUTHOR]

A total monosaccharide concentration of 37.8 g/L and 85.9% conversion from total fermentable monosaccharides of 44.0 g/L from 110 g dw/L Eucheuma denticulatum slurry were obtained by thermal acid hydrolysis and enzymatic saccharification. Subsequent adsorption treatment to remove 5-hydroxymethylfurfural (5-HMF) using 5% activated carbon and an adsorption time of 10 min were used to prevent a prolonged lag phase, reduced cell growth, and low ethanol production. The equilibrium adsorption capacity ( q ) of HMF (58.183 mg/g) showed high affinity to activated carbon comparing to those of galactose (2.466 mg/g) and glucose (2.474 mg/g). The efficiency of cell growth and ethanol production with activated carbon treatment was higher than that without activated carbon treatment. Fermentation using S. stipitis KCTC7228 produced a cell concentration of 3.58 g dw/L with Y of 0.107, and an ethanol concentration of 15.8 g/L with Y of 0.48 in 96 h. [ABSTRACT FROM AUTHOR]

Thermophilic dry methane fermentation is advantageous for feedstock with high solid content. Distillation residue with 65.1 % moisture content was eluted from ethanol fermentation of kitchen waste and subjected to thermophilic dry methane fermentation, after adjusting the moisture content to 75 %. The effect of carbon to nitrogen (C/N) ratio on thermophilic dry methane fermentation was investigated. Results showed that thermophilic dry methane fermentation could not be stably performed for >10 weeks at a C/N ratio of 12.6 and a volatile total solid (VTS) loading rate of 1 g/kg sludge/d; however, it was stably performed at a C/N ratio of 19.8 and a VTS loading rate of 3 g/kg sludge/d with 83.4 % energy recovery efficiency. Quantitative PCR analysis revealed that the number of bacteria and archaea decreased by two orders of magnitude at a C/N ratio of 12.6, whereas they were not influenced at a C/N ratio of 19.8. Microbial community analysis revealed that the relative abundance of protein-degrading bacteria increased and that of organic acid-oxidizing bacteria and acetic acid-oxidizing bacteria decreased at a C/N ratio of 12.6. Therefore, there was accumulation of NH and acetic acid, which inhibited thermophilic dry methane fermentation. [ABSTRACT FROM AUTHOR]

Corn stover (CS) was hydrothermally pretreated using CHCOOH (0.3 %, v/v), and subsequently its ability to be utilized for conversion to ethanol at high-solids content was investigated. Pretreatment conditions were optimized employing a response surface methodology (RSM) with temperature and duration as independent variables. Pretreated CS underwent a liquefaction/saccharification step at a custom designed free-fall mixer at 50 °C for either 12 or 24 h using an enzyme loading of 9 mg/g dry matter (DM) at 24 % (w/w) DM. Simultaneous enzymatic saccharification and fermentation (SSF) of liquefacted corn stover resulted in high ethanol concentration (up to 36.8 g/L), with liquefaction duration having a negligible effect. The threshold of ethanol concentration of 4 % (w/w), which is required to reduce the cost of ethanol distillation, was surpassed by the addition of extra enzymes at the start up of SSF achieving this way ethanol titer of 41.5 g/L. [ABSTRACT FROM AUTHOR]

Cassava pulp (CP), a by-product from the cassava starch industry, is a potential resource for ethanol production. Ammonia gas absorption fiber expansion (AGAFE) was developed to accomplish efficient saccharification of CP. AGAFE was designed to be used under moderate pressure by directly adding compressed ammonia gas before rapidly releasing the pressure. Scanning electron microscopy analysis showed that the cell wall of AGAFE-pretreated CP was severely disrupted, while the fiber of the raw CP remained largely intact. Additionally, the concentration of glucose released from the hydrolysis of pretreated CP was higher than that obtained from raw CP using α-amylase and glucoamylase. The optimum pretreatment conditions for AGAFE were 0.2 MPa and 70 °C for 10 min, which resulted in saccharification of 83.16 % of the total starch in CP. In contrast, only 53.73 % saccharification was achieved when raw CP was directly hydrolyzed without pretreatment, suggesting that destruction of the starch and fiber in CP was necessary to obtain maximum saccharification. To confirm whether the AGAFE pretreatment influenced ethanol fermentation, a fermentation test using the hydrolysate from AGAFE-pretreated CP was carried out using Saccharomyces cerevisiae NCYC3233 and Kluyveromyces marxianus TISTR5925. When the hydrolysates containing 10.1 % ( w/ v) glucose were subjected to fermentation, 5.0 and 4.5 % ( w/ v) ethanol was produced, respectively, indicating that >85 % of the theoretical yields were achieved without inhibition from any mixture components. These results indicated that AGAFE is a useful pretreatment option for ethanol production from biomass containing starch and fiber such as CP. [ABSTRACT FROM AUTHOR]

Dried distillers grains with solubles (DDGS), a co-product of corn ethanol production in the dry-grind process, was pretreated by soaking in aqueous ammonia (SAA) using a 15 % w/ w NHOH solution at a solid/liquid ratio of 1:10. The effect of pretreatment on subsequent enzymatic hydrolysis was studied at two temperatures (40 and 60 °C) and four reaction times (6, 12, 24, and 48 h). Highest glucose yield of 91 % theoretical was obtained for the DDGS pretreated at 60 °C and 24 h. The solubilized hemicellulose in the liquid fraction was further hydrolyzed with dilute HSO to generate fermentable monomeric sugars. The conditions of acid hydrolysis included 1 and 4 wt% acid, 60 and 120 °C, and 0.5 and 1 h. Highest yields of xylose and arabinose were obtained at 4 wt% acid, 120 °C, and 1 h. The fermentability of the hydrolysate obtained by enzymatic hydrolysis of the SAA-pretreated DDGS was demonstrated in ethanol fermentation by Saccharomyces cerevisiae. The fermentability of the hydrolysate obtained by consecutive enzymatic and dilute acid hydrolysis was demonstrated using a succinic acid-producing microorganism, strain Escherichia coli AFP184. Under the fermentation conditions, complete utilization of glucose and arabinose was observed, whereas only 47 % of xylose was used. The succinic acid yield was 0.60 g/g total sugar consumed. [ABSTRACT FROM AUTHOR]

Effects of severe and mild alkaline hydrogen peroxide (AHP) pretreatment on ethanol production from sweet sorghum bagasse via pre-simultaneous saccharification fermentation, and the chemical structure changes of the substrates were investigated. The results showed that the bagasse pretreated by severe AHP could produce more ethanol than that of mild AHP. The maximum ethanol concentration of the bagasses from mild and severe AHP pretreatment with 8% bagasse loading was 7.642±0.140 g/L and 19.330±0.085 g/L, respectively. Moreover, the FTIR and NMR analysis illustrated that the molecule and surface structures of the pretreated bagasse were significantly changed compared with the control. The potential biomass energy production of the effluent from the pretreatment was also briefly discussed for future utilization of waste solution.The heat energy potentials of waste solution with severe and mild AHP pretreatment were 367.2 kJ/L and 327.6 kJ/L, respectively. [ABSTRACT FROM AUTHOR]

Present paper describes a process development for fractionation of holocellulose in rice straw into its monomeric sugars employing acid hydrolysis followed by enzymatic saccharification. Rice straw has been hydrolyzed at 140 °C and 0.6 % v/ v dilute sulfuric acid with 90 min holding time for maximum recovery of pentose monomer (12.52 g xylose/100 g biomass). Pentose stream was used for yeast cell biomass generation. Commercial cellulase resulted in 79 ± 0.05 % saccharification efficiency with acid-hydrolyzed biomass. Fermentation of saccharified broth using thermophilic yeast Kluyveromyces sp. IIPE453 (MTCC 5314) with cell recycle produced ethanol with an overall yield and productivity of 93.5 ± 0.05 % and 0.90 ± 0.2 g/L/h, respectively, and with negligible residual sugar in fermentation broth. Lignin-rich residual biomass had a high gross calorific value and could be used as a source of clean gaseous fuel. [ABSTRACT FROM AUTHOR]

In bioethanol production plants, yeast cells are generally recycled between fermentation batches by using a treatment with sulphuric acid at a pH ranging from 2.0 to 2.5. We have previously shown that Saccharomyces cerevisiae cells exposed to sulphuric acid treatment induce the general stress response pathway, fail to activate the protein kinase A signalling cascade and requires the mechanisms of cell wall integrity and high osmolarity glycerol pathways in order to survive in this stressful condition. In the present work, we used transcriptome-wide analysis as well as physiological assays to identify the transient metabolic responses of S. cerevisiae under sulphuric acid treatment. The results presented herein indicate that survival depends on a metabolic reprogramming of the yeast cells in order to assure the yeast cell viability by preventing cell growth under this harmful condition. It involves the differential expression of a subset of genes related to cell wall composition and integrity, oxidation-reduction processes, carbohydrate metabolism, ATP synthesis and iron uptake. These results open prospects for application of this knowledge in the improvement of industrial processes based on metabolic engineering to select yeasts resistant to acid treatment. [ABSTRACT FROM AUTHOR]

To overcome the xylose utilization defect in ethanol fermentation by wide-type Saccharomyces cerevisiae and alleviate the carbon catabolite repression (CCR) in acetone-butanol-ethanol (ABE) fermentation by Clostridium acetobutylicum, a novel mixed fermentation of S. cerevisiae and C. acetobutylicum was developed. When S. cerevisiae was inoculated 24 h earlier than C. acetobutylicum CH02, a higher solvents yield was achieved with 0.41 g/g, compared to 0.38 g/g in ABE fermentation, and when S. cerevisiae and C. acetobutylicum CH02 were inoculated simultaneously, a higher productivity was achieved with 0.32 g/L/h, compared to 0.15 g/L/h in ABE fermentation. The total solvents yield was improved by the high ethanol yield from glucose. The CCR in mixed fermentation was alleviated when glucose was utilized quickly by S. cerevisiae, and therefore, the productivity was improved. This study suggests that mixed fermentation is an effective solvents production method from a mixture of glucose and xylose. [ABSTRACT FROM AUTHOR]

A total monosaccharide concentration of 39.6 g/L, representing 74.0 % conversion of 53.5 g/L total carbohydrate from 80 g dw/L (8 % w/v) Gracilaria verrucosa slurry, was obtained by thermal acid hydrolysis and enzymatic saccharification. G. verrucosa hydrolysate was used as a substrate for ethanol production by 'separate hydrolysis and fermentation' (SHF). The ethanol production and yield ( Y) from Saccharomyces cerevisiae KCCM 1129 with and without adaptation to high galactose concentrations were 18.3 g/L with Y of 0.46 and 13.4 g/L with Y of 0.34, respectively. Relationship between galactose adaptation effects and mRNA transcriptional levels were evaluated with GAL gene family, regulator genes of the GAL genetic switch and repressor genes in non-adapted and adapted S. cerevisiae. The development of galactose adaptation for ethanol fermentation of G. verrucosa hydrolysates allowed us to enhance the overall ethanol yields and obtain a comprehensive understanding of the gene expression levels and metabolic pathways involved. [ABSTRACT FROM AUTHOR]

This study compared the ethanol productivity of different yeast strains using three different seaweed species as fermentation feedstocks. Each seaweed was saccharified by treatment with 3 % (v/v) sulfuric acid and cellulase. Ulva spp., Gracilaria spp. and Costaria costata yielded 0.22, 0.16, and 0.10 g of reducing sugars per 1 g of dried seaweed powder, respectively. Among the yeast strains tested, the marine-derived C-19 had maximum ethanol productivity, with production of 0.15, 0.08, and 0.05 g of ethanol from saccharified solutions containing 1 g of Ulva spp., Gracilaria spp., and C. costata powder, respectively. By the optimization of pretreatment, saccharification and fermentation conditions, C-19 yeast became capable of producing 0.09 g of ethanol from the alginate-extracted residue of C. costata. Finally, to evaluate the robustness of our measurements, we performed scale-up saccharification and fermentation using a jar fermentor. The productivity of both saccharification and fermentation were similar across both scales. Thus, we confirmed that the ethanol fermentation conditions from seaweeds powders in this study are appropriate even at larger scales. [ABSTRACT FROM AUTHOR]

High-efficiency xylose utilization is one of the restrictive factors of bioethanol industrialization. However, xylonic acid (XA) as a new bio-based platform chemical can be produced by oxidation of xylose with microbial. So, an applicable technology of XA bioconversion was integrated into the process of bioethanol production. After corn stover was pretreated with acid-catalyzed steam-explosion, solid and liquid fractions were obtained. The liquid fraction, also named as acid-catalyzed steam-exploded corn stover (ASC) prehydrolyzate (mainly containing xylose), was catalyzed with Gluconobacter oxydans NL71 to prepare XA. After 72 h of bioconversion of concentrated ASC prehydrolyzate (containing 55.0 g/L of xylose), the XA concentration reached a peak value of 54.97 g/L, the sugar utilization ratio and XA yield were 94.08 and 95.45 %, respectively. The solid fraction was hydrolyzed to produce glucose with cellulase and then fermented with Saccharomyces cerevisiae NL22 to produce ethanol. After 18 h of fermentation of concentrated enzymatic hydrolyzate (containing 86.22 g/L of glucose), the ethanol concentration reached its highest value of 41.48 g/L, the sugar utilization ratio and ethanol yield were 98.72 and 95.25 %, respectively. The mass balance showed that 1 t ethanol and 1.3 t XA were produced from 7.8 t oven dry corn stover. [ABSTRACT FROM AUTHOR]

Previously, it was shown that the gas produced in an ethanol fermentor using either corn or barley as feedstock could be sparged directly into an adjacent fermentor as a feedstock for succinic acid fermentation using Escherichia coli AFP184. In the present investigation, it was demonstrated that the CO produced in a corn ethanol fermentor could be absorbed in a base solution and the resultant carbonate solution used both for pH control and supply of the CO requirement in succinic acid fermentation. Thus, the CO produced in a 5-L corn mash containing 30 wt% total solids was absorbed in a packed column containing 2 L of either 5 M NaOH, 5 M KOH, or 15 wt% NHOH, and the resultant carbonate solutions were used for pH control in a succinic acid fermentor. The results obtained indicated no significant differences between succinic acid production in these experiments and when 2.5 M solutions of NaCO, KCO, and (NH)CO from commercial sources were used. In a commercial setting, the demonstrated capture of CO in liquid form will allow transportation of the carbonate solutions to locations not in the immediate vicinity of the ethanol plant, and excess carbonate salts can also be recovered as value-added products. [ABSTRACT FROM AUTHOR]

Phytic acid present in raw materials used in distilling industry can form complexes with starch and divalent cations and thus limit their biological availability. The influence of the enzymatic hydrolysis of phytate complexes on starch availability during the alcoholic fermentation process using high gravity (HG) maize mashes was analyzed. Indicators of the alcoholic fermentation as well as the fermentation activity of Saccharomyces cerevisiae D-2 strain were statistically evaluated. Phytate hydrolysis improved the course of the alcoholic fermentation of HG maize mashes. The final ethanol concentration in the media supplemented with phytase applied either before or after the starch hydrolysis increased by 1.0 and 0.6 % v/ v, respectively, as compared to the control experiments. This increase was correlated with an elevated fermentation yield that was higher by 5.5 and 2.0 L EtOH/100 kg of starch, respectively. Phytate hydrolysis resulted also in a statistically significant increase in the initial concentration of fermenting sugars by 14.9 mg/mL of mash, on average, which was a consequence of a better availability of starch for enzymatic hydrolysis. The application of phytase increased the attenuation of HG media fermentation thus improving the economical aspect of the ethanol fermentation process. [ABSTRACT FROM AUTHOR]

High temperature ethanol fermentation from sugarcane molasses B using thermophilic Crabtree-positive yeast Kluyveromyces sp. IIPE453 was carried out in batch bioreactor system. Strain was found to have a maximum specific ethanol productivity of 0.688 g/g/h with 92 % theoretical ethanol yield. Aeration and initial sugar concentration were tuning parameters to regulate metabolic pathways of the strain for either cell mass or higher ethanol production during growth with an optimum sugar to cell ratio 33:1 requisite for fermentation. An assessment of ethanol recovery from fermentation broth via simulation study illustrated that distillation-based conventional recovery was significantly better in terms of energy efficiency and overall mass recovery in comparison to coupled solvent extraction-azeotropic distillation technique for the same. [ABSTRACT FROM AUTHOR]

Consolidated bioprocessing of lignocellulose for ethanol production is realized by expressing cellulase enzymes on ethanologenic strain. In this study, an ethanologenic Escherichia coli ZY81 was constructed by integrating pyruvate decarboxylase gene pdc and alcohol dehydrogenase gene adhB from Zymomonas mobilis into the genome of E. coli JM109 to obtain the capability of ethanol production. Then, the β-glucosidase gene bglB from Bacillus polymyxa was cloned and secretively expressed in E. coli ZY81. The recombinant strain E. coli ZY81/ bglB showed an obvious activity of β-glucosidase in extracellular location with more than half in periplasmic space. EDTA was found to promote the release of the periplasmic proteins by approximately tenfold. E. coli ZY81/ bglB utilized cellobiose as sole carbon source for ethanol production with 33.99 % of theoretical yield. [ABSTRACT FROM AUTHOR]

Saccharomyces cerevisiae, industrial yeast isolate, has been of great interest in recent years for fuel ethanol production. The ethanol yield and productivity depend on many inhibitory factors during the fermentation process such as temperature, ethanol, compounds released as the result of pretreatment procedures, and osmotic stress. An ideal strain should be able to grow under different stress conditions occurred at different fermentation steps. Development of tolerant yeast strains can be achieved by reprogramming pathways supporting the ethanol metabolism by regulating the energy balance and detoxicification processes. Complex gene interactions should be solved for an in-depth comprehension of the yeast stress tolerance mechanism. Genetic engineering as a powerful biotechnological tool is required to design new strategies for increasing the ethanol fermentation performance. Upregulation of stress tolerance genes by recombinant DNA technology can be a useful approach to overcome inhibitory situations. This review presents the application of several genetic engineering strategies to increase ethanol yield under different stress conditions including inhibitor tolerance, ethanol tolerance, thermotolerance, and osmotolerance. [ABSTRACT FROM AUTHOR]

Whole-genome shuffling (WGS) is a powerful technology of improving the complex traits of many microorganisms. However, the molecular mechanisms underlying the altered phenotypes in isolates were less clarified. Isolates with significantly enhanced stress tolerance and ethanol titer under very-high-gravity conditions were obtained after WGS of the bioethanol Saccharomyces cerevisiae strain ZTW1. Karyotype analysis and RT-qPCR showed that chromosomal rearrangement occurred frequently in genome shuffling. Thus, the phenotypic effects of genomic structural variations were determined in this study. RNA-Seq and physiological analyses revealed the diverse transcription pattern and physiological status of the isolate S3-110 and ZTW1. Our observations suggest that the improved stress tolerance of S3-110 can be largely attributed to the copy number variations in large DNA regions, which would adjust the ploidy of yeast cells and expression levels of certain genes involved in stress response. Overall, this work not only constructed shuffled S. cerevisiae strains that have potential industrial applications but also provided novel insights into the molecular mechanisms of WGS and enhanced our knowledge on this useful breeding strategy. [ABSTRACT FROM AUTHOR]

The yeast Dekkera bruxellensis is considered to be very well adapted to industrial environments, in Brazil, USA, Canada and European Countries, when different substrates are used in alcoholic fermentations. Our previous study described its fermentative profile with a sugarcane juice substrate. In this study, we have extended its physiological evaluation to fermentation situations by using sugarcane molasses as a substrate to replicate industrial working conditions. The results have confirmed the previous reports of the low capacity of D. bruxellensis cells to assimilate sucrose, which seems to be the main factor that can cause a bottleneck in its use as fermentative yeast. Furthermore, the cells of D. bruxellensis showed a tendency to deviate most of sugar available for biomass and organic acids (lactic and acetic) compared with Saccharomyces cerevisiae, when calculated on the basis of their respective yields. As well as this, the acetate production from molasses medium by both yeasts was in marked contrast with the previous data on sugarcane juice. Glycerol and ethanol production by D. bruxellensis cells achieved levels of 33 and 53 % of the S. cerevisiae, respectively. However, the ethanol yield was similar for both yeasts. It is worth noting that this yeast did not accumulate trehalose when the intracellular glycogen content was 30 % lower than in S. cerevisiae. The lack of trehalose did not affect yeast viability under fermentation conditions. Thus, the adaptive success of D. bruxellensis under industrial fermentation conditions seems to be unrelated to the production of these reserve carbohydrates. [ABSTRACT FROM AUTHOR]

The amylose/amylopectin ratio in cereal substrates is one of the parameters affecting starch hydrolysis and fermentation process. Waxy (less than 1 mass % of amylose) starch seems to be suitable for improving the fuel ethanol production. The main aim of this paper was to characterize the fermentation performance of corn and wheat waxy and non-waxy cultivars in terms of simultaneous saccharification and fermentation (SSF) as well as of the separated hydrolysis and fermentation (SHF) type. Two corn (waxy and non-waxy) and two wheat (waxy and non-waxy) cultivars were used for the comparison applying separate enzymatic hydrolysis and fermentation. In the SHF process, the glucose content was higher after saccharification in the waxy corn and wheat compared to that in non-waxy corn and wheat. In the SSF of waxy varieties, the glucose content after the pre-saccharification was also higher than in the non-waxy ones. Although the starch content did not vary significantly, differences in the glucose content after saccharification were observed. The ethanol yield obtained after the distillation of mash varied from 229.2–262.3 L per ton for the SHF fermentation, while it was in the range of 311.5–347.9 L per ton for the SSF process. [ABSTRACT FROM AUTHOR]

In this work, a new approach for acetone-butanol-ethanol (ABE) production has been proposed. Direct fermentation of native starches (uncooked process) was investigated by using granular starch hydrolyzing enzyme (GSHE) and Clostridium saccharoperbutylacetonicum N1-4. Even the process was carried out under suboptimal condition for activity of GSHE, the production of ABE was similar with that observed in conventional process or cooked process in terms of final solvent concentration (21.3 ± 0.4 to 22.4 ± 0.4 g/L), butanol concentration (17.5 ± 0.4 to 17.8 ± 0.3 g/L) and butanol yield (0.33 to 0.37 g/g). The production of solvents was significantly dependent on the source of starches. Among investigated starches, corn starch was more susceptible to GSHE while cassava starch was the most resistant to this enzyme. Fermentation using native corn starch resulted in the solvent productivity of 0.47 g/L h, which was about 15 % higher than that achieved in cooked process. On the contrary, uncooked process using cassava and wheat starch resulted in the solvent productivity of 0.30 and 0.37 g/L h, which were respectively about 30 % lower than those obtained in cooked process. No contamination was observed during all trials even fermentation media were prepared without sterilization. During the fermentation using native starches, no formation of foam is observed. This uncooked process does not require cooking starchy material; therefore, the thermal energy consumption for solvent production would remarkably be reduced in comparison with cooked process. [ABSTRACT FROM AUTHOR]

This work focuses on the kinetics of ethanol production by Scheffersomyces stipitis on xylose with the development of a mathematical model considering the effect of substrate and product concentrations on growth rate. Experiments were carried out in batch and continuous modes, with substrate concentration varying from 7.2 to 145 g L. Inhibitory effects on cell growth, substrate uptake, and ethanol production rates were found to be considerable. Kinetic parameters were obtained through linear and non-linear regression methods. Experiments in continuous mode were performed at different dilution rates to evaluate the inhibitory effect of ethanol. A mixed mathematical model which combined Andrews and Levenspiel's models, combining substrate and product inhibition, was used. A quasi-Newton routine was applied to obtain a more accurate fitting of kinetic parameters. The parameters such as cell to product factor ( Y) and limiting cell yield ( Y) were shown to be dependent on substrate concentration. The kinetic model fitted satisfactorily the experimental data. [ABSTRACT FROM AUTHOR]