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Background: Clostridium thermocellum is a promising candidate for production of cellulosic biofuels, however, its final product titer is too low for commercial application, and this may be due to thermodynamic limitations in glycolysis. Previous studies in this organism have revealed a metabolic bottleneck at the phosphofructokinase (PFK) reaction in glycolysis. In the wild-type organism, this reaction uses pyrophosphate (PPi) as an energy cofactor, which is thermodynamically less favorable compared to reactions that use ATP as a cofactor. Previously we showed that replacing the PPi-linked PFK reaction with an ATP-linked reaction increased the thermodynamic driving force of glycolysis, but only had a local effect on intracellular metabolite concentrations, and did not affect final ethanol titer. Results: In this study, we substituted PPi-pfk with ATP-pfk, deleted the other PPi-requiring glycolytic gene pyruvate:phosphate dikinase (ppdk), and expressed a soluble pyrophosphatase (PPase) and pyruvate kinase (pyk) genes to engineer PPi-free glycolysis in C. thermocellum. We demonstrated a decrease in the reversibility of the PFK reaction, higher levels of lower glycolysis metabolites, and an increase in ethanol titer by an average of 38% (from 15.1 to 21.0 g/L) by using PPi-free glycolysis. Conclusions: By engineering PPi-free glycolysis in C. thermocellum, we achieved an increase in ethanol production. These results demonstrate that optimizing the thermodynamic landscape through metabolic engineering can enhance product titers. While further increases in ethanol titers are necessary for commercial application, this work represents a significant step toward engineering glycolysis in C. thermocellum to increase ethanol titers. [ABSTRACT FROM AUTHOR]

Electrochemical CO2 reduction reaction (CO2RR) to produce chemicals and fuels is a promising strategy to achieve carbon neutrality. However, due to the slow C─C coupling kinetics and the fact that C2H5OH and C2H4 products share the same *HCCOH intermediate, achieving high activity and selectivity for C2H5OH remains challenging. This paper describes an atmosphere‐induced reconstruction method to optimize the surface composition and coordination structure of the CuxZny bimetallic alloy catalysts for C2H5OH production. Specifically, the CuxZny alloy catalyst treated within CO atmosphere (CO‐CuxZny) enriches with low‐coordinated Cu sites, which are favorable for the adsorption of the *CO intermediates for promoted C2H5OH production. A C2+ Faradaic efficiency (FE) of 85.1% and a C2H5OH FE of 59.5% are achieved by the CO‐Cu84Zn16 at a current density of 300 mA cm−2. In‐situ spectroscopic studies and DFT calculations demonstrate that the enhanced *CO adsorption promotes the C─C coupling process. At the same time, the hydrogenation of *HCCOH is more favorable on CO‐Cu84Zn16 to inhibit the C2H4 pathway, thus enhancing the generation of C2H5OH. This study provides an effective strategy to regulate the selectivity of CO2RR through the control of the surface coordination environment of the active sites. [ABSTRACT FROM AUTHOR]

The dried bark of Eucalyptus grandis (EG) was treated in alkaline (NaOH) and alkaline peroxide (NaOH along with H2O2) solution at 60 °C (AHP-60), 80 °C (AHP-80) and in an autoclave at 121 °C and a pressure of 15 lb/ in 2 (AAHP). The structural and chemical changes during pretreatment with alkaline and alkaline peroxide were observed through FTIR, XRD analysis and DNS assay. The effects of NaOH and H2O2 concentration and temperature on lignin removal efficiency and production of reducing sugar were studied. Kinetic parameters of enzymatic hydrolysis and fermentation were evaluated. The results indicated the removal of lignin and easy accessibility of cellulose as the crystallinity of the pretreated Eucalyptus grandis increased. The lignin removal was highest (73.20%) for AAHP. A maximum reducing sugar yield of 215.5 mg/g was also obtained from the same pretreatment conditions confirming the recalcitrance nature of lignin is the key inhibitory factor for the production of reducing sugars. During enzymatic hydrolysis, glucose concentration is observed to be increased over time with the increase in substrate concentration for a particular enzyme loading. EG in AAHP upon enzymatic hydrolysis generates the highest amount of reducing sugar and yields better ethanol conversion (9.941 g/g). The kinetic parameters from hydrolysis and fermentation indicate no inhibition of enzymes by substrate and product. [ABSTRACT FROM AUTHOR]

Photocatalytic CH4 oxidation to ethanol with high selectivity is attractive but substantially challenging. The activation of inert C−H bonds at ambient conditions requires highly reactive oxygen species like hydroxyl radicals (⋅OH), while the presence of those oxidative species also facilitates fast formation of C1 products, instead of the kinetically sluggish C−C coupling to produce ethanol. Herein, we developed a BiVO4 photocatalyst with surface functionalization of Au nanoparticles (BiVO4@Au), which not only enables photogeneration of ⋅OH to activate CH4 into ⋅CH3, but also in situ consumes those ⋅OH species to retard their further attack on ⋅CH3, resulting in an enhanced ⋅CH3/⋅OH ratio and facilitating C−C coupling toward ethanol. The ⋅CH3/⋅OH ratio is further improved by transporting CH4 via a gas‐diffusion layer to the photocatalytic interface, leading to even higher ethanol selectivity and production rates. At ambient conditions and without photosensitizers or sacrificial agents, the BiVO4@Au photocatalyst exhibited an outstanding CH4‐to‐ethanol conversion performance, including a peak ethanol yield of 680 μmol ⋅ g−1 ⋅ h−1, a high selectivity of 86 %, and a stable photoconversion of >100 h, substantially exceeding most of the previous reports. Our work suggests an attractive approach of in situ generation and modulation of the ⋅OH levels for photocatalytic CH4 conversion toward multi‐carbon products. [ABSTRACT FROM AUTHOR]

Efficient CO2 electroreduction (CO2RR) to ethanol holds promise to generate value‐added chemicals and harness renewable energy simultaneously. Yet, it remains an ongoing challenge due to the competition with thermodynamically more preferred ethylene production. Herein, we presented a CO2 reduction predilection switch from ethylene to ethanol (ethanol‐to‐ethylene ratio of ~5.4) by inherently implanting Cu sites with perfluorooctane to create interfacial noncovalent interactions. The 1.83 %F‐Cu2O organic–inorganic hybrids (OIHs) exhibited an extraordinary ethanol faradaic efficiency (FEethanol) of ∼55.2 %, with an impressive ethanol partial current density of 166 mA cm−2 and excellent robustness over 60 hours of continuous operation. This exceptional performance ranks our 1.83 %F‐Cu2O OIHs among the best‐performing ethanol‐oriented CO2RR electrocatalysts. Our findings identified that C8F18 could strengthen the interfacial hydrogen bonding connectivity, which consequently promotes the generation of active hydrogen species and preferentially favors the hydrogenation of *CHCOH to *CHCHOH, thus switching the reaction from ethylene‐preferred to ethanol‐oriented. The presented investigations highlight opportunities for using noncovalent interactions to tune the selectivity of CO2 electroreduction to ethanol, bringing it closer to practical implementation requirements. [ABSTRACT FROM AUTHOR]

Acetic acid is a common inhibitor present in lignocellulose hydrolysate, which inhibits the ethanol production by yeast strains. Therefore, the cellulosic ethanol industry requires yeast strains that can tolerate acetic acid stress. Here we demonstrate that overexpressing a yeast native arginase-encoding gene, CAR1, renders Saccharomyces cerevisiae acetic acid tolerance. Specifically, ethanol yield increased by 27.3% in the CAR1-overexpressing strain compared to the control strain under 5.0 g/L acetic acid stress. The global intracellular amino acid level and compositions were further analyzed, and we found that CAR1 overexpression reduced the total amino acid content in response to acetic acid stress. Moreover, the CAR1 overexpressing strain showed increased ATP level and improved cell membrane integrity. Notably, we demonstrated that the effect of CAR1 overexpression was independent of the spermidine and proline metabolism, which indicates novel mechanisms for enhancing yeast stress tolerance. Our studies also suggest that CAR1 is a novel genetic element to be used in synthetic biology of yeast for efficient production of fuel ethanol. [ABSTRACT FROM AUTHOR]

Sugarcane cultivation requires sustainable strategies to meet water and nutritional needs. This study tested the hypothesis that irrigation with treated sewage effluent (TSE) can meet the water needs of sugarcane plants, improving their technological quality and yield. The objective of this study was to assess the effects of subsurface drip irrigation (SDI) with TSE or surface reservoir water (SRW) on soil chemical characteristics and technological quality and productivity. Thus, an SDI system was installed at soil depths of 0.20 and 0.40 m to apply SRW and TSE to sugarcane plants, composing four irrigation treatments (TSE0.2 m, TSE0.4 m, SRW0.2 m and SRW0.4 m) and a control (non-irrigated treatment). Analyses of soil chemical characteristics in different layers showed no negative effects for the use of SDI, which maintained favorable soil conditions for sugarcane plantations. The surface layer (0–0.2 m) irrigated with SRW or TSE showed higher accumulation of nutrients and organic matter. The results confirmed the hypothesis that irrigation with TSE or SRW improves the technological quality and yield of sugarcane; the treatment TSE0.2 m showed the best results regarding increases in sugar yield and alcohol production. However, continuous monitoring of soil salinity is necessary in wastewater-irrigated agricultural systems. [ABSTRACT FROM AUTHOR]

Fruit and vegetables waste are a promising feedstock for production of ethanol have garnering significant attention due to its potential and environmentally sound energy source including reducing waste sent to landfills, providing a source of renewable energy, and reducing reliance on fossil fuels. In this study, fruit wastes from orange, pomegranate, and papaya, as well as vegetable wastes from potatoes, tomatoes, and carrots, were selected as feedstocks for ethanol production. Orange, pomegranate, and papaya wastes exhibited the highest concentrations of fermentable sugars, followed by tomato and carrot wastes. The fermentation of these feedstock using appropriate microorganisms resulted in the production of ethanol with yields ranging from 25 to 50%. The analysis of ethanol performance results showed that orange, pomegranate, papaya, and potato samples were within allowable range whereas tomato and carrot samples were above the allowable range. Moreover, the purified ethanol used in the experiment was clear and colourless. This paper conclude that fruit and vegetable waste represent a promising feedstock for ethanol production showing the highest potential for ethanol production. However, further research is required to optimize fermentation processes and address challenges of using these feedstock and processing for scalable ethanol production. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the nutritional requirements of Saccharomyces cerevisiae to improve low ethanol production in some fruit wines. The growth kinetics, ethanol production and nutrient requirements of S. cerevisiae were analyzed in chemically defined media. The results revealed that Ca2+, Fe2+, Co2+, Mo2+, Cu2+ and BO33− were predominantly utilized during the late lag phase, whereas free amino acids, nicotinic acid, calcium pantothenate, Na+ and Mg2+ were mainly consumed during the logarithmic phase. Compared with the control medium, supplementation with threonine, inositol, calcium pantothenate, thiamine hydrochloride, riboflavin, biotin, MgSO4 or KH2PO4 significantly increased the ethanol content by 1.10-fold (p < 0.05). Furthermore, adding key nutrients to noni-, guava- and mango juice significantly shortened the fermentation time and increased the final alcohol content of the fruit wines (p < 0.05). This study provides scientific insights and effective methods for shortening fermentation time and increasing alcohol content with S. cerevisiae in some fruit wines. [ABSTRACT FROM AUTHOR]

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Abstract Background Clostridium thermocellum is a promising candidate for production of cellulosic biofuels, however, its final product titer is too low for commercial application, and this may be due to thermodynamic limitations in glycolysis. Previous studies in this organism have revealed a metabolic bottleneck at the phosphofructokinase (PFK) reaction in glycolysis. In the wild-type organism, this reaction uses pyrophosphate (PPi) as an energy cofactor, which is thermodynamically less favorable compared to reactions that use ATP as a cofactor. Previously we showed that replacing the PPi-linked PFK reaction with an ATP-linked reaction increased the thermodynamic driving force of glycolysis, but only had a local effect on intracellular metabolite concentrations, and did not affect final ethanol titer. Results In this study, we substituted PPi-pfk with ATP-pfk, deleted the other PPi-requiring glycolytic gene pyruvate:phosphate dikinase (ppdk), and expressed a soluble pyrophosphatase (PPase) and pyruvate kinase (pyk) genes to engineer PPi-free glycolysis in C. thermocellum. We demonstrated a decrease in the reversibility of the PFK reaction, higher levels of lower glycolysis metabolites, and an increase in ethanol titer by an average of 38% (from 15.1 to 21.0 g/L) by using PPi-free glycolysis. Conclusions By engineering PPi-free glycolysis in C. thermocellum, we achieved an increase in ethanol production. These results demonstrate that optimizing the thermodynamic landscape through metabolic engineering can enhance product titers. While further increases in ethanol titers are necessary for commercial application, this work represents a significant step toward engineering glycolysis in C. thermocellum to increase ethanol titers.

Low-carbon ammonia production is crucial for sustainable development. Brazil, a top ethanol producer, can boost competitiveness and cut emissions by integrating ammonia and ethanol production. However, optimal location and production strategy identification is challenging due to existing possibilities and uncertainties. For that, a new MILP superstructure with robust optimisation was developed and used to analyse low-carbon ammonia production integration in the ethanol industry in São Paulo state by ethanol and biomethane routes, in two different scenarios. As for the results, in scenario 1, biomethane and ethanol investments were USD 3.846 M and USD 314 M. In scenario 2, the investments were USD 316 M for biomethane and USD 259 M for ethanol. Despite the higher investment, the biomethane route results in lower hydrogen production cost (USD 1880/tonne) due to raw material prices; however, ethanol displays a higher hydrogen potential, consuming just 8% of total production against 54% of vinasse availability, which is used for biodigestion and biomethane production. In conclusion, the results suggest that the northern region of São Paulo has greater potential for ammonia facilities due to resource availability. These findings can inform and support more comprehensive studies and public incentive policies. [ABSTRACT FROM AUTHOR]

The bacterium Zymomonas mobilis is investigated as a model organism for the cultivation and separation of ethanol as a product by in situ extraction in continuous flow microreactors. The considered microreactor is the Coiled Flow Inverter (CFI), which consists of a capillary coiled onto a support structure. Like other microreactors, the CFI benefits from a high surface-to-volume ratio, which enhances mass and heat transfer. Compared to many other microreactors, the CFI offers the advantage of operating without internal structures, which are often used to ensure good mixing. The simplicity of the design makes the CFI particularly suitable for biochemical applications as cells do not get stuck or damaged by internal structures. Despite this simplicity, good mixing is achieved through flow vortices caused by Taylor and Dean vortices. The reaction system consists of two phases, in which the aqueous phase carries the bacterium and an oleyl alcohol phase is used to extract the ethanol produced. Key parameters for evaluation are bacteria growth and the amount of ethanol produced by the microorganism. The results show the suitability of the CFI for microbial production of valuable compounds. A maximum ethanol concentration of 1.26 g L−1 was achieved for the experiment in the CFI. Overall, the cultivation in the CFI led to faster growth of Z. mobilis, resulting in 25% higher ethanol production than in conducted batch experiments. [ABSTRACT FROM AUTHOR]

Thailand is globally recognized for its rich biodiversity, a characteristic that extends to the diverse species of indigenous yams within the Dioscorea spp. genus. With the energy crisis, the selection of agricultural materials for ethanol production to replace the use of economic crops is therefore necessary. This research focuses on six specific yam varieties: Amorphophallus konjac, Colocasia esculenta, Dioscorea bulbifera, Dioscorea alata, Dioscorea hispida, and Dioscorea esculenta. The primary objective is to investigate their bioethanol productivity through the implementation of a separate hydrolysis and fermentation process, with the broader aim of contributing to the potential preservation of these invaluable indigenous yam species. Initiating the study, the experimental samples underwent hydrolysis by alpha-amylase enzyme (1% w/winitial starch) for 180 min, followed by glucoamylase enzyme (1% w/winitial starch) for an additional 72 h. Post the initial hydrolysis, the detection of small molecule sugars by high-performance liquid chromatography, revealed a range of 14.49 ± 1.10 to 28.89 ± 0.03 gtotal sugar/L, with maltose emerging as the predominant sugar compound. Subsequent to the second hydrolysis, it was observed that maltose and starch residues across all six samples underwent successful digestion. The peak glucose productivity was attained at the 12-h mark post-glucoamylase hydrolysis. Among the diverse yam varieties under examination, Dioscorea hispida exhibited the highest glucose production, showcasing a hydrolysis efficiency of 62.53 ± 2.08%. Following the fermentation process with S. cerevisiae, the optimal fermentation time was identified as 72 h, at which point all available glucose in the hydrolysate was fully utilized. The bioethanol productivity spanned from 32.31 ± 3.40 to 43.66 ± 0.02 g/L, with Dioscorea hispida demonstrating the highest ethanol productivity at 0.61 ± 0.00 g/L/h, and a yield of 0.42 ± 0.01gEtOH/gGlucose. These findings underscore the potential of Dioscorea hispida as a promising contributor to bioethanol production. [ABSTRACT FROM AUTHOR]

This study explores the potential of producing bioethanol from seaweed biomass and reusing the residues as antioxidant compounds. Various types of seaweed, including red (Gelidium amansii, Gloiopeltis furcata, Pyropia tenera), brown (Saccharina japonica, Undaria pinnatifida, Ascophyllum nodosum), and green species (Ulva intestinalis, Ulva prolifera, Codium fragile), were pretreated with dilute acid and enzymes and subsequently processed to produce bioethanol with Saccharomyces cerevisiae BY4741. Ethanol production followed the utilization of sugars, resulting in the highest yields from red algae > brown algae > green algae due to their high carbohydrate content. The residual biomass was extracted with water, ethanol, or methanol to evaluate its antioxidant activity. Among the nine seaweeds, the A. nodosum bioethanol residue extract (BRE) showed the highest antioxidant activity regarding the 2,2-diphenyl-1-picrylhydrazyl (DPPH) activity, ferric reducing antioxidant power (FRAP), and reactive oxygen species (ROS) inhibition of H2O2-treated RAW 264.7 cells. These by-products can be valorized, contributing to a more sustainable and economically viable biorefinery process. This dual approach not only enhances the utilization of marine resources but also supports the development of high-value bioproducts. [ABSTRACT FROM AUTHOR]

Saccharomyces cerevisiae is considered the most promising large-scale production strain with ethanol as the main product. The fermentation of Saccharomyces cerevisiae is generally inhibited under various stress conditions. Various inhibitors in the hydrolysate severely inhibit yeast proliferation and yeast accumulation. In this study, S. cerevisiae ERG5, NTH1, and AMS1 were knocked out to improve the yeast stress tolerance by the Clustered Regularly Interspaced Short Palindromic Repeats Cas9 (CRISPR-Cas9) technology. The result indicated that the stress tolerance of S. cerevisiae ERG5ΔNTH1ΔAMS1Δ mutant (S. cerevisiae SCENA) was remarkably improved compared with the wild-type strain. The contents of fecosterol, trehalose, and mannan in S. cerevisiae SCENA were 1.67, 1.53, and 1.47 folds compared with those in the control. The ethanol concentration in S. cerevisiae SCENA reached 16.5 g/L, which was 1.23 folds compared with the control using rice bran hydrolysate. Further, the transcriptome analysis indicated down-regulated differential expression genes (DEGs) in S. cerevisiae SCENA were mainly from cellular response to glucose, cell periphery, and plasma membrane. Up-regulated DEGs were mainly from spore wall assembly, fungal-type cell wall assembly, and ascospore wall assembly. Thus, S. cerevisiae SCENA could effectively produce ethanol using the fermentation of lignocellulosic hydrolysate in the presence of inhibitors by regulating fecosterol, trehalose, and mannan metabolisms.

Cu‐based catalysts have been shown to selectively catalyze CO2 photoreduction to C2+ solar fuels. However, they still suffer from poor activity and low selectivity. Herein, we report a high‐performance carbon nitride supported Cu single‐atom catalyst featuring defected low‐coordination Cu‐N2 motif (Cu‐N2‐V). Lead many recently reported photocatalysts and its Cu‐N3 and Cu‐N4 counterparts, Cu‐N2‐V exhibits superior photocatalytic activity for CO2 reduction to ethanol and delivers 69.8 μmol g−1 h−1 ethanol production rate, 97.8 % electron‐based ethanol selectivity, and a yield of ~10 times higher than Cu‐N3 and Cu‐N4. Revealed by the extensive experimental investigation combined with DFT calculations, the superior photoactivity of Cu‐N2‐V stems from its defected Cu‐N2 configuration, in which the Cu sites are electron enriched and enhance electron delocalization. Importantly, Cu in Cu‐N2‐V exist in both Cu+ and Cu2+ valence states, although predominantly as Cu+. The Cu+ sites support the CO2 activation, while the co‐existence of Cu+/Cu2+ sites are highly conducive for strong *CO adsorption and subsequent *CO‐*CO dimerization enabling C−C coupling. Furthermore, the hollow microstructure of the catalyst also promotes light adsorption and charge separation efficiency. Collectively, these make Cu‐N2‐V an effective and high‐performance catalyst for the solar‐driven CO2 conversion to ethanol. This study also elucidates the C‐C coupling reaction path via *CO‐*CO to *COCOH and rate‐determining step, and reveals the valence state change of partial Cu species from Cu+ to Cu2+ in Cu‐N2‐V during CO2 photoreduction reaction. [ABSTRACT FROM AUTHOR]

Marine macroalgae waste, resulting from the accumulation of drifted algal biomass along the coastline, might be a relevant complementary raw material aiming sustainable bioethanol production. In the present study, the optimisation of thermal acid hydrolysis was performed using response surface methodology (RSM) considering the effect of three variables, namely, reaction time (10–60 min), acid concentration (0.1–2.5% (v/v) H2SO4) and biomass:acid ratio (5–15% (w/v)) on sugar concentration and yield. Under the best conditions, the resulting hydrolysates were fermented (7 days, 30 °C, 150 rpm, commercial yeast) to produce bioethanol. A statistically valid second-order model was obtained (r2 = 0.9876; Prob > F lower than 0.05), showing that sugar concentration is mostly influenced by the biomass:acid ratio while reaction time was not significant. The maximum predicted sugar concentration was 18.4 g/L, being obtained at 2.5% H2SO4 concentration and 15% (w/v) biomass:acid ratio, corresponding to a sugars yield of 12.5 g/100 g (less 36% than that obtained using 10% (w/v)). At the best conditions, the hydrolysates were fermented to obtain a bioethanol concentration up to 2.4 g/L and a 21 mgbioethanol/gbiomass yield, emphasizing the biomass potential for bioenergy production. [ABSTRACT FROM AUTHOR]

This study evaluates the stress tolerance and metabolic adaptability of twelve yeast strains, including eleven commercial strains from Wyeast Laboratories and one prototrophic laboratory strain, under industrially relevant conditions. Yeast strains were assessed for their fermentation performance and stress responses under glucose limitation, osmotic stress, acid stress, elevated ethanol concentrations, and temperature fluctuations. Results revealed significant variability in glucose consumption, ethanol production, and stress tolerance across strains. ACY34 and ACY84 demonstrated the highest fermentation efficiency, while ACY19 exhibited exceptional stress resilience, excelling under multiple stress conditions such as osmotic and ethanol stress. The findings highlight strain-specific performance, with some strains suited for high-yield fermentation and others excelling under challenging environmental conditions. These results provide critical insights for selecting and optimizing yeast strains tailored to specific industrial fermentation processes, contributing to improved productivity and product quality in food and beverage production.

The concept of 'Energy from waste' is one of the most focused areas of work to find a solution for controlling trash and combat energy crises. In Pakistan and other agricultural countries, because of their substantial use during the summer, watermelon peels as fruit waste are usually thrown out as a trash. This study supported the management of huge quantities of waste to value-added products at a commercial scale. The current study aims to select and subject xylanolytic and ethanologenic Bacillus cereus XG2 for water melon peels valorization appropriately with comparison of three hydrolysis techniques. The study will be helpful for selection of economical and environmentally beneficial valorization strategies. For ethanalogenesis, separate hydrolysis and fermentation (SHF) protocols with Saccharomyces cerevisiae K7 and Metchnikowia cibodasensis Y34 were used. For hydrolysis, three different saccharification approaches, viz. dilute sulfuric acid, enzymatic hydrolysis (using Bacillus cereus XG2 xylanases), and combined acidic and enzymatic hydrolysis, were adopted. Two statistical models, Placket-Burman (hydrolysis) and Central composite design (ethanologenesis) were used. In untreated watermelon waste (WW), reducing sugar, total lipids, total carbohydrates, and protein contents were calculated as 16.70±0.05 g/L, 3.20±0.02 g/L, 28.7±0.04 g/L, and 3.70±0.03 g/L, respectively. Similarly, the lignin (15.51±0.22%), hemicellulose (17.20±2.30%). and cellulose (52.26±0.33%) contents were also analyzed. Based on the significance of the Plackett–Burman model for enzymatic saccharification, the released reducing sugars as well as total sugars were 21.62±0.01 g/L and 43.30±1.55 g/L, respectively, and enzymatic hydrolyzate was adopted for further fermentation experiments. By CCD model, the highest ethanol yield calculated for yeast Metchnikowia cibodasensis Y34 was 0.4±0.04 g/g of fermentable sugars at 32.5o C with 50% enzymatic hydrolysate of WW by incubating for 8 days. It was suggested that SHF could be a beneficial approach to increase the conversion of hemicellulose to fermentable sugars to produce bioethanol on a large scale. [ABSTRACT FROM AUTHOR]

Biofuels, especially ethanol, have gained immense popularity in the global energy sector, driven by a significant increase in demand. Ethanol production using agroindustrial residues reduces costs and can provide a destination for these residues that are generally wasted. In this context, the cashew apple emerges as an attractive and unconventional feedstock for bioethanol production. Although the technology to obtain ethanol from cashew apple juice is present in several studies, the key elements that determine its economic feasibility have never been defined. Then, this study aimed to present the first techno-economic assessment of ethanol production from cashew apple juice. Two industrial full-detailed scenarios were proposed based on the application of the obtained ethanol, where in scenario I, 2.1 × 106 liters of ethanol are produced for combustion purposes (94% w/w), while in scenario II, 2.8 × 106 liters of ethanol are produced for antiseptic purposes (70% w/w). The yields calculated in the proposed scenarios I and II were 66.5 L/ton and 88.9 L/ton, respectively, values comparable with those found in the literature using sugar cane and sweet sorghum as feedstocks. Then, the production of ethanol from cashew apple juice proved technically feasible. Economic sensibility analysis showed that both proposed scenarios are economically viable, as long as the cashew apple acquisition cost is at most 17.2 US$/ton for the scenario I and 28.1 US$/ton for scenario II. The raw material cost was the most crucial parameter to impact the economic analysis. In conclusion, the proposed biorefinery returned promising results, and it can consolidate a new raw material for ethanol production, provided that idle capacity is reduced and heat generation from cashew apple bagasse is optimized. [ABSTRACT FROM AUTHOR]

Saccharomyces cerevisiae is one of the prominent strains in the brewing and bioethanol industries and has been used for many industrial purposes for ages. Though the organism is an outstanding ethanol producer, the major limiting factor is the stress the organism undergoes during fermentation. One of the significant stresses is the ethanol stress, created by ethanol accumulation in the medium. The ethanol starts to interact with the yeast cell membrane; further, as ethanol concentration increases, it affects a lot of cell organelles. Thereby, cellular activities get disrupted, causing cell death and hence reducing ethanol production. The organism has developed many strategies to overcome this stress by activating the stress response pathway, which regulates many genes involved in modifying the cell membrane cell wall, renaturation of proteins, and altering the metabolism. However, with higher ethanol concentrations, the yeast cells will be unable to tolerate, leading to cell death. Hence, to minimize cell death at higher ethanol concentrations, there is a need to understand the effect of ethanol and its response by the organism; this helps improve the ethanol tolerance of the organism and, thereby, ethanol production. Although many research works are carried out to understand the vital aspect of the tolerance and are reported, very few review papers cover all these points. Hence, this review is designed to include information on all the elements of ethanol tolerance, i.e., ethanol tolerance of different strains of S. cerevisiae , the effect of ethanol on the yeast cells, the mechanism used to tolerate the ethanol, and various techniques developed to improve the ethanol tolerance of the yeast cells. [Display omitted] • Saccharomyces cerevisiae: key in brewing, bioethanol; historic importance; widespread applications. • Detailed exploration of ethanol's harmful effects on yeast, disrupting cellular activities and reducing ethanol production. • Explore ethanol stress adaptations, emphasizing stress response pathway's role in cell component modification. • Addressing the challenge of ethanol tolerance, emphasizing the importance of minimizing cell death for enhanced production. [ABSTRACT FROM AUTHOR]

Biofuels have gained significant attention as an alternative energy source for transportation worldwide due to concerns about oil depletion, energy security, and global warming. However, the biofuel sector is also acknowledged as a significant contributor to environmental impacts, resulting in various forms of pollution that harm water, soil, air quality, and human health. To address and minimize these environmental consequences, evaluating the impact of the entire biofuel supply chain becomes crucial. This study conducts a comprehensive life cycle assessment (LCA) of ethanol production from sugarcane in northern India. The analysis encompasses the entire process from sugarcane farming, sugarcane transportation, and biorefinery processing, with 1 ton of ethanol as the functional unit. The environmental correlations of all inputs and outputs in the LCA research were assessed using SimaPro version 9.0 and the ReCiPe Midpoint and Endpoint methods to estimate their potential environmental impact. The findings highlight the substantial contributions of molasses and electricity to all impact categories, accounting for an average of 73.01 percent for the former and 23.02 percent for the latter respectively. For each ton of ethanol produced, the GWP is 585.95 kg CO2-eq, with 392.93 kg CO2-eq from molasses practices and an additional 186.05 kg CO2-eq from coal-based electricity. Further, the study proposes an alternative scenario to emphasize the importance of adopting a multi-perspective approach for mitigating the environmental impact of biofuel production. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the nutritional requirements of Saccharomyces cerevisiae to improve low ethanol production in some fruit wines. The growth kinetics, ethanol production and nutrient requirements of S. cerevisiae were analyzed in chemically defined media. The results revealed that Ca2+, Fe2+, Co2+, Mo2+, Cu2+ and BO33− were predominantly utilized during the late lag phase, whereas free amino acids, nicotinic acid, calcium pantothenate, Na+ and Mg2+ were mainly consumed during the logarithmic phase. Compared with the control medium, supplementation with threonine, inositol, calcium pantothenate, thiamine hydrochloride, riboflavin, biotin, MgSO4 or KH2PO4 significantly increased the ethanol content by 1.10-fold (p < 0.05). Furthermore, adding key nutrients to noni-, guava- and mango juice significantly shortened the fermentation time and increased the final alcohol content of the fruit wines (p < 0.05). This study provides scientific insights and effective methods for shortening fermentation time and increasing alcohol content with S. cerevisiae in some fruit wines.

The bacterium Zymomonas mobilis is investigated as a model organism for the cultivation and separation of ethanol as a product by in situ extraction in continuous flow microreactors. The considered microreactor is the Coiled Flow Inverter (CFI), which consists of a capillary coiled onto a support structure. Like other microreactors, the CFI benefits from a high surface-to-volume ratio, which enhances mass and heat transfer. Compared to many other microreactors, the CFI offers the advantage of operating without internal structures, which are often used to ensure good mixing. The simplicity of the design makes the CFI particularly suitable for biochemical applications as cells do not get stuck or damaged by internal structures. Despite this simplicity, good mixing is achieved through flow vortices caused by Taylor and Dean vortices. The reaction system consists of two phases, in which the aqueous phase carries the bacterium and an oleyl alcohol phase is used to extract the ethanol produced. Key parameters for evaluation are bacteria growth and the amount of ethanol produced by the microorganism. The results show the suitability of the CFI for microbial production of valuable compounds. A maximum ethanol concentration of 1.26 g L−1 was achieved for the experiment in the CFI. Overall, the cultivation in the CFI led to faster growth of Z. mobilis, resulting in 25% higher ethanol production than in conducted batch experiments.

Ethanol is becoming the important renewable energy sources in the world which produces from carbohydrate resources. The raw material selection is the important procedure for real industrial production. The effect of biomass structural composition in feedstock on ethanol production is therefore needed to explore for feedstock selection. According to the previous research studies, the fermentation process includes pre-treatment and fermentation of sugar to ethanol. This study focuses on the simulation of raw material variation in ethanol production especially the structural composition of carbohydrate that contains three main components, cellulose, xylan, and lignin, in the fermentation section. The simulation model is validated by the data of previous study information with small deviation. The mixture design method is used for result interpretation and analysis. From the design of experiment, there are 14 scenarios and the selected response parameter is the mass fraction of ethanol in outlet stream of fermentation section. From the results, the maximum mass fraction of ethanol in outlet stream is in the scenario which has a large amount of cellulose and xylan fractions. This is because the conversion of reaction in the fermentation reactor mostly consumes cellulose and xylan to produce glucose and xylose, respectively, and converts them into ethanol product. From the overall result of this study, the important of raw material selection in ethanol production is illustrated.

Sparassis crispa contains various bioactive substances, such as β-glucan, which exhibits antitumor activity. In this study, we investigated the effect of the mycelial shape of S. crispa and the combination of flask type and agitation method on β-glucan production. With the combination of the Erlenmeyer flask and shaken culture, the mycelia grew in the shape of pellets, whereas with the combination of the baffled Erlenmeyer flask and stirred culture, the mycelia grew in the shape of filaments. The dried cell weight (DCW) and β-glucan production of the filamentous mycelia were 5.91 g/L and 1.71 g/L, respectively, 1.34-fold and 1.73-fold higher, respectively, than that of the pelleted mycelia (4.42 g/L and 0.99 g/L, respectively). The production was further increased using the homogenization process; the DCW was 1.03-fold (7.23 g/L) higher and β-glucan production 1.34-fold (3.50 g/L) higher, respectively, than that without the treatment (7.01 g/L and 2.61 g/L, respectively). In the filamentous mycelia, β-glucan production increased with suppressed ethanol production, and a negative correlation was observed between β-glucan production and ethanol production. In the cultivation of S. crispa mycelia, filamentous mycelia have been suggested to be more suitable for β-glucan production than pelleted mycelia. [ABSTRACT FROM AUTHOR]

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Recently, the extensive spread of some algae along coastlines has surged into unmanageable thick decomposition layers. This study aimed to demonstrate the use of Sargassum horneri as a biomass resource for ethanol production through the continuous hydrolysis, enzymatic saccharification, and fermentation process. Sugars from S. horneri were obtained using a combination of thermal acid hydrolysis and enzymatic saccharification. The optimal conditions for thermal acid hydrolysis involved a 10% (w/v) S. horneri slurry treated with 100 mM H2SO4 at 121 °C for 60 min; enzymatic saccharification using 16 U/mL Cellic CTec2 further boosted the monosaccharide concentration to 23.53 g/L. Fermentation experiments were conducted with mannitol-adapted Saccharomyces cerevisiae BY4741 using S. horneri hydrolysate. Enhanced ethanol production was observed in the hydrolysate, particularly with mannitol-adapted S. cerevisiae BY4741, which yielded 10.06 g/L ethanol. Non-adapted S. cerevisiae produced 8.12 g/L ethanol, as it primarily utilized glucose and not mannitol. Regarding ethanol fermentation using 5 L- and 500 L-scale fermenters, the ethanol concentrations reached 10.56 g/L and 7.88 g/L with yields of 0.51 and 0.45, respectively, at 48 h. This study confirmed the economic viability of ethanol production using waste seaweed with optimized pretreatment conditions and the adaptive evolution of S. cerevisiae to mannitol. [ABSTRACT FROM AUTHOR]

Background: Mathematical modeling of a fermentation process is crucial in understanding and predicting dynamics of the process, which can be used in process improvement, design and control. The present study aimed to develop Monod-based kinetic models to describe cell growth, substrate consumption and ethanol production by Saccharomyces cerevisiae NP 01 under high gravity (HG) fermentation of sweet sorghum juice (SSJ). Results: The fermentation using an initial total sugar (TS) concentration of 240 g/L resulted in 113.3 g/L of ethanol production, with 90.9% TS consumption and a fermentation efficiency of 94.4%. Growth of the yeast in terms of specific growth rate was found to be inhibited at a threshold TS concentration of 65 g/L, and the maximum specific growth rate, Monod constant and inhibition constant were 0.45 1/h, 19.5 g/L and 0.002 L/(g·h), respectively. Monod-based models incorporating substrate and product inhibition terms showed high applicability to describe the changes of cell, TS and ethanol concentrations, based on the values of bias factor, accuracy factor, coefficient of determination and root mean square error. Conclusions: The Monod-based models fitted the data equally well as compared with the logistic, modified Gompertz, and Weibull models, despite estimating the value of different kinetic parameters. These results demonstrated that all the models tested were applicable in modeling HG ethanol fermentation.How to cite: Salakkam A, Phukoetphim N, Laopaiboon P, et al. Mathematical modeling of bioethanol production from sweet sorghum juice under high gravity fermentation: Applicability of Monod-based, logistic, modified Gompertz and Weibull models. Electron J Biotechnol 2023;64. https://doi.org/10.1016/j.ejbt.2023.03.004.

This study explores the potential of producing bioethanol from seaweed biomass and reusing the residues as antioxidant compounds. Various types of seaweed, including red (Gelidium amansii, Gloiopeltis furcata, Pyropia tenera), brown (Saccharina japonica, Undaria pinnatifida, Ascophyllum nodosum), and green species (Ulva intestinalis, Ulva prolifera, Codium fragile), were pretreated with dilute acid and enzymes and subsequently processed to produce bioethanol with Saccharomyces cerevisiae BY4741. Ethanol production followed the utilization of sugars, resulting in the highest yields from red algae > brown algae > green algae due to their high carbohydrate content. The residual biomass was extracted with water, ethanol, or methanol to evaluate its antioxidant activity. Among the nine seaweeds, the A. nodosum bioethanol residue extract (BRE) showed the highest antioxidant activity regarding the 2,2-diphenyl-1-picrylhydrazyl (DPPH) activity, ferric reducing antioxidant power (FRAP), and reactive oxygen species (ROS) inhibition of H2O2-treated RAW 264.7 cells. These by-products can be valorized, contributing to a more sustainable and economically viable biorefinery process. This dual approach not only enhances the utilization of marine resources but also supports the development of high-value bioproducts.

Hal5 gene is involved in halo-tolerance of Saccharomyces cerevisiae during high salt stress. Ethanol stress and high salt stress have similarities, as both decrease the availability of water for cells and strain the osmotic homeostasis across the cell membrane. The Hal5 over-expression strain of yeast has more ethanol tolerance, but the Hal5 null mutant strain also has more ethanol tolerance than the wild-type strain. Hal5 over-expression in this yeast strain may help in adaptation to ethanol stress by way of directly stabilizing the proteins (trk1-trk2) that are responsible for maintaining osmotic homeostasis. Dysfunction of Hal5 in the null mutant may result in increased trehalose, which also stabilizes proteins and increases ethanol tolerance in comparison to wild type, although not as much as over-expression of Hal5. In biochemical assays and FTIR, we observed an increase in trehalose in Hal5 mutant in comparison to the wild-type, as well as a further increase in response to ethanol stress. The ethanol stress increases ROS, protein carbonylation, and lipid peroxidation in all strains, but the Hal5 over-expression and Hal5 null mutation mitigate these adverse effects of ethanol stress.

Bamboo is considered a renewable energy bioresource for solving the energy crisis and climate change. Dendrocalamus branddisii (DB) was first subjected to sulfomethylation reaction at 95°C for 3 h, followed by Fenton oxidation pretreatment at 22°C for 24 h. The synergistic effect of combined pretreatment dramatically improved enzymatic digestibility efficiency, with maximum yield of glucose and ethanol content of 71.11% and 16.47 g/L, respectively, increased by 4.7 and 6.11 time comparing with the single Fenton oxidation pretreatment. It was found that the hydrophobicity of substrate, content of surface lignin, degree of polymerization, and specific surface area have significant effects on the increase of enzymatic saccharification efficiency. It also revealed that sulfomethylation pre-extraction can improve the hydrophilicity of lignin, leading to the lignin dissolution, which was beneficial for subsequent Fenton pretreatment of bamboo biomass. This work provides some reference for Fenton oxidation pretreatment of bamboo biomass, which can not only promote the utilization of bamboo in southwest China, but also enhances the Fenton reaction in the bamboo biorefinery.

Increased human population and the rapid decline of fossil fuels resulted in a global tendency to look for alternative fuel sources. Environmental concerns about fossil fuel combustion led to a sharp move towards renewable and environmentally friendly biofuels. Ethanol has been the primary fossil fuel alternative due to its low carbon emission rates, high octane content and comparatively facile microbial production processes. In parallel to the increased use of bioethanol in various fields such as transportation, heating and power generation, improvements in ethanol production processes turned out to be a global hot topic. Ethanol is by far the leading yeast output amongst a broad spectrum of bio-based industries. Thus, as a well-known platform microorganism and native ethanol producer, baker's yeast Saccharomyces cerevisiae has been the primary subject of interest for both academic and industrial perspectives in terms of enhanced ethanol production processes. Metabolic engineering strategies have been primarily adopted for direct manipulation of genes of interest responsible in mainstreams of ethanol metabolism. To overcome limitations of rational metabolic engineering, an alternative bottom-up strategy called inverse metabolic engineering has been widely used. In this context, evolutionary engineering, also known as adaptive laboratory evolution (ALE), which is based on random mutagenesis and systematic selection, is a powerful strategy to improve bioethanol production of S. cerevisiae. In this review, we focus on key examples of metabolic and evolutionary engineering for improved first- and second-generation S. cerevisiae bioethanol production processes. We delve into the current state of the field and show that metabolic and evolutionary engineering strategies are intertwined and many metabolically engineered strains for bioethanol production can be further improved by powerful evolutionary engineering strategies. We also discuss potential future directions that involve recent advancements in directed genome evolution, including CRISPR-Cas9 technology. [ABSTRACT FROM AUTHOR]

Potato peel waste (PPW), a zero‐value by‐product generated from potato processing, is a promising fermentation substrate due to its large quantity of starch, nonstarch polysaccharides, lignin, protein, and lipid. Rhizopus oryzae is a filamentous fungus that is mainly known as a lactic acid producer and can ferment various agro‐wastes. This study aimed to use R. oryzae for the fermentation of PPW. A series of batch fermentations were conducted to investigate the effects of different PPW loading rates (2%–8%) and particle sizes (0–4 mm). Under an initial PPW loading rate of 8% and particle size of 1–2 mm, the maximum ethanol (18.83 g/L) and lactic acid (3.14 g/L) concentrations, the highest ethanol (9.41 g/L·day) and lactic acid (1.89 g/L·day) average production rates were obtained. Under these conditions, the yield of ethanol and lactic acid was 0.235 g/gPPW and 0.039 g/gPPW, respectively. R. oryzae was shown to utilize PPW as a substrate to produce value‐added bioproducts such as ethanol (major product) and lactic acid. [ABSTRACT FROM AUTHOR]

Photoconversion of CO2 and H2O into ethanol is an ideal strategy to achieve carbon neutrality. However, the production of ethanol with high activity and selectivity is challenging owing to the less efficient reduction half‐reaction involving multi‐step proton‐coupled electron transfer (PCET), a slow C−C coupling process, and sluggish water oxidation half‐reaction. Herein, a two‐dimensional/two‐dimensional (2D/2D) S‐scheme heterojunction consisting of black phosphorus and Bi2WO6 (BP/BWO) was constructed for photocatalytic CO2 reduction coupling with benzylamine (BA) oxidation. The as‐prepared BP/BWO catalyst exhibits a superior photocatalytic performance toward CO2 reduction, with a yield of 61.3 μmol g−1 h−1 for ethanol (selectivity of 91 %).In situ spectroscopic studies and theoretical calculations reveal that S‐scheme heterojunction can effectively promote photogenerated carrier separation via the Bi−O−P bridge to accelerate the PCET process. Meanwhile, electron‐rich BP acts as the active site and plays a vital role in the process of C−C coupling. In addition, the substitution of BA oxidation for H2O oxidation can further enhance the photocatalytic performance of CO2 reduction to C2H5OH. This work opens a new horizon for exploring novel heterogeneous photocatalysts in CO2 photoconversion to C2H5OH based on cooperative photoredox systems. [ABSTRACT FROM AUTHOR]

Abstract Background The thermotolerant yeast is beneficial in terms of efficiency improvement of processes and reduction of costs, while Saccharomyces cerevisiae does not efficiently grow and ferment at high-temperature conditions. The sterol composition alteration from ergosterol to fecosterol in the cell membrane of S. cerevisiae affects the thermotolerant capability. Results In this study, S. cerevisiae ERG5, ERG4, and ERG3 were knocked out using the CRISPR–Cas9 approach to impact the gene expression involved in ergosterol synthesis. The highest thermotolerant strain was S. cerevisiae ERG5ΔERG4ΔERG3Δ, which produced 22.1 g/L ethanol at 37 °C using the initial glucose concentration of 50 g/L with an increase by 9.4% compared with the wild type (20.2 g/L). The ethanol concentration of 9.4 g/L was produced at 42 ℃, which was 2.85-fold of the wild-type strain (3.3 g/L). The molecular mechanism of engineered S. cerevisiae at the RNA level was analyzed using the transcriptomics method. The simultaneous deletion of S. cerevisiae ERG5, ERG4, and ERG3 caused 278 up-regulated genes and 1892 down-regulated genes in comparison with the wild-type strain. KEGG pathway analysis indicated that the up-regulated genes relevant to ergosterol metabolism were ERG1, ERG11, and ERG5, while the down-regulated genes were ERG9 and ERG26. S. cerevisiae ERG5ΔERG4ΔERG3Δ produced 41.6 g/L of ethanol at 37 °C with 107.7 g/L of corn liquefied glucose as carbon source. Conclusion Simultaneous deletion of ERG5, ERG4, and ERG3 resulted in the thermotolerance improvement of S. cerevisiae ERG5ΔERG4ΔERG3Δ with cell viability improvement by 1.19-fold at 42 °C via modification of steroid metabolic pathway. S. cerevisiae ERG5ΔERG4ΔERG3Δ could effectively produce ethanol at 37 °C using corn liquefied glucose as carbon source. Therefore, S. cerevisiae ERG5ΔERG4ΔERG3Δ had potential in ethanol production at a large scale under supra-optimal temperature.

Ethanol production in Brazil started in the early 1930s due to laws created by the Brazilian government. However, ethanol production only increased significantly with the National Program of Ethanol implementation in 1975. This program was another action taken by the Brazilian government aiming to provide conditions for the development of the ethanol industry in the country. With the program, it was possible to achieve significant progress; however, it finished in the mid-1980s. Currently, ethanol is produced on a large scale by more than 300 sugarcane mills all over the country. In 2016, the Brazilian government provided another incentive for ethanol production by creating the RenovaBio Program, which aimed to reduce greenhouse gas emissions. Besides the environmental aspect, Brazil’s ethanol industry needs to develop to supply future biofuel demand. According to the forecast provided in this paper, and considering technical, economic, and environmental aspects regarding the Brazilian ethanol industry, the current and only feedstock used is likely to be insufficient. Thus, the ethanol produced from corn would be an attractive secondary feedstock to complement sugarcane ethanol as the primary feedstock.

Abstract Background Industrial bioethanol production may involve a low pH environment caused by inorganic acids, improving the tolerance of Saccharomyces cerevisiae to a low pH environment is of industrial importance to increase ethanol yield, control bacterial contamination, and reduce production cost. In our previous study, acid tolerance of a diploid industrial Saccharomyces cerevisiae strain KF-7 was chronically acclimatized by continuous ethanol fermentation under gradually increasing low-pH stress conditions. Two haploid strains B3 and C3 having excellent low pH tolerance were derived through the sporulation of an isolated mutant. Diploid strain BC3 was obtained by mating these two haploids. In this study, B3, C3, BC3, and the original strain KF-7 were subjected to comparison transcriptome analysis to investigate the molecular mechanism of the enhanced phenotype. Result The comparison transcriptome analysis results suggested that the upregulated vitamin B1 and B6 biosynthesis contributed to the low pH tolerance. Amino acid metabolism, DNA repairment, and general stress response might also alleviate low pH stress. Conclusion Saccharomyces cerevisiae seems to employ complex regulation strategies to tolerate low pH during ethanol production. The findings provide guides for the construction of low pH-tolerant industrial strains that can be used in industrial fermentation processes.

Background: Mathematical modeling of a fermentation process is crucial in understanding and predicting dynamics of the process, which can be used in process improvement, design and control. The present study aimed to develop Monod-based kinetic models to describe cell growth, substrate consumption and ethanol production by Saccharomyces cerevisiae NP 01 under high gravity (HG) fermentation of sweet sorghum juice (SSJ). Results: The fermentation using an initial total sugar (TS) concentration of 240 g/L resulted in 113.3 g/L of ethanol production, with 90.9% TS consumption and a fermentation efficiency of 94.4%. Growth of the yeast in terms of specific growth rate was found to be inhibited at a threshold TS concentration of 65 g/L, and the maximumspecific growth rate, Monod constant and inhibition constant were 0.45 1/h, 19.5 g/L and 0.002 L/(g-h), respectively. Monod-based models incorporating substrate and product inhibition terms showed high applicability to describe the changes of cell, TS and ethanol concentrations, based on the values of bias factor, accuracy factor, coefficient of determination and root mean square error. Conclusions: The Monod-based models fitted the data equally well as compared with the logistic, modified Gompertz, and Weibull models, despite estimating the value of different kinetic parameters. These results demonstrated that all the models tested were applicable in modeling HG ethanol fermentation. [ABSTRACT FROM AUTHOR]

On the basis of its properties, ethanol has been identified as the most used biofuel because of its remarkable contribution in reducing emissions of carbon dioxide which are the source of greenhouse gas and prompt climate change or global warming worldwide. The use of ethanol as a new source of biofuel reduces the dependence on conventional gasoline, thus showing a decreasing pattern of production every year. This article contains an updated overview of recent developments in the new technologies and operations in ethanol production, such as the hydration of ethylene, biomass residue, lignocellulosic materials, fermentation, electrochemical reduction, dimethyl ether, reverse water gas shift, and catalytic hydrogenation reaction. An improvement in the catalytic hydrogenation of CO2 into ethanol needs extensive research to address the properties that need modification, such as physical, catalytic, and chemical upgrading. Overall, this assessment provides basic suggestions for improving ethanol synthesis as a source of renewable energy in the future. [ABSTRACT FROM AUTHOR]

To effectively utilize local fruit residue resources and regulate ethanol production in fermented feed, the impact of moisture adjustment, lactic acid bacteria (LAB) inoculant, and chemical additive on the fermentation characteristics and ethanol production of total mixed ration (TMR) containing apple pomace was studied. The TMR was prepared with apple pomace, corn, wheat bran, soybean meal, timothy, and alfalfa hay. The mixing proportion of apple pomace was 15% based on dry matter (DM). In experiment 1, the moisture in TMR was unadjusted (control) or adjusted to 45, 50, and 55%, respectively. TMR containing 55% moisture was used in experiment 2, and the treatments were control, homo-fermentative LAB (Lactobacillus plantarum, LP), hetero-fermentative LAB (Lactobacillus buchneri, LB), and calcium propionate (CaP). The laboratory-scale fermentation system was used to prepare TMR, and their fermentation characteristics were analyzed after 60 days of ensiling. In experiment 1, the pH of the various TMRs was around 4.1. As the moisture decreased, lactic acid increased (p < 0.05) and ammonia-N decreased (p < 0.05). The ethanol decreased significantly with moisture adjustment compared to the control and the TMR with 50% moisture had the lowest ethanol content (p < 0.05). In experiment 2, LP treatment increased lactic acid, and decreased acetic acid and ammonia-N significantly (p < 0.05), while LB treatment had no effect on fermentation. LP and LB each had no effect on the ethanol content. TMR treated with CaP significantly decreased the ethanol and acetic acid content (p < 0.05), but did not inhibit lactic acid production compared to control. The results confirmed that adjusting the moisture of TMR to 50% and adding CaP could effectively inhibit the excessive production of ethanol in TMR of apple pomace. Homofermentative LAB can better improve the fermentation quality of TMR than heterofermentative LAB, but neither can inhibit the production of ethanol. This is of great significance to the effective utilization of apple residue resources and the promotion of livestock production. [ABSTRACT FROM AUTHOR]

The objective of this work was to test the Fenton reaction on pretreatment of elephant grass aiming the results of cellulose increase and the delignification process. A subsequent study of the enzymatic hydrolysis of the pretreated elephant grass and the mathematical modeling of hydrolysis was performed. A Doehlert-type experimental design was used into the pretreatment stage and the best results were obtained at the central point with an average of 53.80% of cellulose and 10.00% of lignin. The enzymatic hydrolysis of pretreated grass with Fenton reaction was performed, with a commercial enzyme, where the best yield (17.39%) of reducing sugars was obtained with 20 g L−1 of enzyme in 72 h and higher productivity (2.51 g L−1 h−1) observed in 2 h. It was possible to adjust the proposed mathematical model to the hydrolysis process. It was observed that, for higher concentrations of enzyme, the proposed mathematical model adjusts better the experimental results (R2 = 0.993). It can be observed with these results that there was an increment in the economic profitability of the enzymatic hydrolysis process due to the relation of the operational parameters, so that it can be used in new projects and industrial applications. [ABSTRACT FROM AUTHOR]