High Ethanol Production Research Articles

Repeated batches as a strategy for high 2G ethanol production from undetoxified hemicellulose hydrolysate using immobilized cells of recombinant Saccharomyces cerevisiae in a fixed-bed reactor

BackgroundThe search for sustainable energy sources has become a worldwide issue, making the development of efficient biofuel production processes a priority. Immobilization of second-generation (2G) xylose-fermenting Saccharomyces cerevisiae strains is a promising approach to achieve economic viability of 2G bioethanol production from undetoxified hydrolysates through operation at high cell load and mitigation of inhibitor toxicity. In addition, the use of a fixed-bed reactor can contribute to establish an efficient process because of its distinct advantages, such as high conversion rate per weight of biocatalyst and reuse of biocatalyst.ResultsThis work assessed the influence of alginate entrapment on the tolerance of recombinant S. cerevisiae to acetic acid. Encapsulated GSE16-T18SI.1 (T18) yeast showed an outstanding performance in repeated batch fermentations with cell recycling in YPX medium supplemented with 8 g/L acetic acid (pH 5.2), achieving 10 cycles without significant loss of productivity. In the fixed-bed bioreactor, a high xylose fermentation rate with ethanol yield and productivity values of 0.38 gethanol/gsugars and 5.7 g/L/h, respectively were achieved in fermentations using undetoxified sugarcane bagasse hemicellulose hydrolysate, with and without medium recirculation.ConclusionsThe performance of recombinant strains developed for 2G ethanol production can be boosted strongly by cell immobilization in alginate gels. Yeast encapsulation allows conducting fermentations in repeated batch mode in fixed-bed bioreactors with high xylose assimilation rate and high ethanol productivity using undetoxified hemicellulose hydrolysate.

Potential of barley straw for high titer bioethanol production applying pre-hydrolysis and simultaneous saccharification and fermentation at high solid loading

Barley straw (BS) is considered a good candidate for fuel-ethanol production due to its abundance and high carbohydrate content. Economic viability of the process requires ethanol titer in fermentation broth >4% (w/v) which is considered to be the benchmark for an efficient distillation. Mild alkaline pretreatment of BS resulted in 74% and 45% lignin and hemicellulose removal, respectively. Alkali treated barley straw (ATBS) was hydrolyzed at 15% (w/v) substrate concentration, using commercial cellulases (Cellic® CTec2). Highest glucose release was 91.19 g/L (hydrolysis yield 82%). Models based on first and second order cellulase deactivation kinetics satisfactory predicted the behavior of glucose release during enzymatic hydrolysis of ATBS, however the first order model appears to fit better. ATBS, at high solids loading (15% and 20% w/v), was converted to bioethanol applying pre-hydrolysis and simultaneous saccharification and fermentation (PSSF). Highest ethanol production was achieved after 16 h pre-hydrolysis. As substrate loading increased from 15% to 20%, ethanol concentration increased from 39.55 to 46.62 g/L. Mass balance of PSSF showed that the reduction of ethanol yield when solid loading increases could be attributed to the decrease in cellulose enzymatic conversion.

Yeast biomass production with potential for biological control: process strategies for increasing yield

The quality of vegetable products is directly linked to the techniques used in the field, in order to ensure safe and healthy products to health. In this context, the use of yeasts with potential for biological control proved to be a promising alternative to assure the safety of these foods. Fermentation processes have been used to promote the development of many products, including the production of yeast biomass. The objective of this work was to verify the influence of the aeration rate and the fed batch process in the production of yeast biomass. A yeast strain with biological control potential, belonging to Embrapa's Semi-Arid crop collection, was subjected to simple batch cultivation and fed with different aeration rates (3, 4, 6 and 8 L.ar/min) and concentration of carbon source in the feed medium (200, 400 and 600 g/L). The highest biomass (6.99 g/L) after 24 hours of fermentation was observed in the experiment that used an aeration rate of 8 L.ar/min. Regarding the concentration of the carbon source in the feed medium, it was found that the concentration of 200 g/L favored a greater total biomass (11.21 g/L) and reduced the production of ethanol (0.65 g/L ), while the concentration of 600 g/L favored less biomass production (7.90 g/L) and higher ethanol production (9.26 g/L). Thus, it was found that the aeration rate and the fed batch process favor the fermentation strategy, as they contribute to the production of yeast biomass and the overall yield of the process.

Response Surface ‎Methodology for Optimization of Ethanol ‎Production from Cocoa Waste

Cocoa waste (CW) is an inexpensive agro-industrial by-product that is available in large quantities in tropical countries such as Malaysia. The rate of ethanol production can be affected by different parameters involved during fermentation. In this study, response surface methodology (RSM) with the full factorial design was used to obtain optimum conditions for bioethanol production using CW as the substrate. The simultaneous saccharification and fermentation (SSF) performed with an isolated microorganism from locally fermented food tapai ubi and tapai pulut. The effect of four independent variables temperature, CW concentration, inoculum size, and pH was investigated. In the optimized condition temperature of 31.7°C, pH 6.0, inoculum size 10.5%, and CW concentration 0.3 g/L, the highest ethanol production was 9.5 ± 1.1. ANOVA analysis revealed that temperature and CW concentration had the most significant effects on ethanol production. In addition, ethanol production was increased in the highest level of pH and inoculum size. Therefore it can be concluded that ethanol production increased from 6.2 ± 0.8 g/L to 9.5 ± 1.1 g/L after optimization.

Endogenous ethanol produced by intestinal bacteria induces mitochondrial dysfunction in non-alcoholic fatty liver disease.

A causal relationship between changes of the gut microbiome and non-alcoholic fatty liver disease (NAFLD) remains unclear. We demonstrated that endogenous ethanol (EnEth) produced by intestinal microbiota is likely a causative agent of NAFLD. Two mutants with different alcohol-producing abilities, namely, W14-adh and W14Δadh, were constructed using the clinical high alcohol-producing (HiAlc) Klebsiella pneumoniae strain W14 as a parent. Damage to hepatocytes caused by bacteria with different alcohol-producing capacities was evaluated (EtOH group as positive control). The ultrastructural changes of mitochondria were assessed via transmission electron microscopy (TEM). Hepatic levels of mitochondrial reactive oxygen species (ROS), DNA damage, and adenosine triphosphate were examined. The results illustrated that steatosis was most severe in the W14-adh group, followed by the W14 group, whereas the W14Δadh group had few fatty droplets. TEM and examination of related protein expression revealed that the mitochondrial integrity of HepG2 hepatocytes was considerably damaged in the EtOH and bacteria treatment groups. The impaired mitochondrial function in HepG2 hepatocytes was evidenced by reduced adenosine triphosphate content and increased mitochondrial ROS accumulation and DNA damage in the EtOH and bacteria treatment groups, especially the W14-adh group. Meanwhile, liver injury and mitochondrial damage were observed in the hepatocytes of mice. The livers of mice in the W14-adh group, which had the highest ethanol production, exhibited the most serious damage, similar to that in the EtOH group. EnEth produced by HiAlc bacteria induces mitochondrial dysfunction in NAFLD.

Biochar-mediated enhanced ethanol fermentation (BMEEF) in Zymomonas mobilis under furfural and acetic acid stress

BackgroundPretreatment of lignocellulosic biomass generates different types of inhibitors (e.g., furfural and acetic acid), which could remarkably inhibit subsequent ethanol fermentation. Here, biochar as an additive in the fermentation broth was first applied to enhance ethanol production by Z. mobilis wild-type strain ZM4 in the presence of typical inhibitors.ResultsThis study showed that the biochar-mediated tolerance to furfural and acetic acid for the strain Z. mobilis ZM4 was the highest reported level, resulting in much higher ethanol productivity under stress conditions than that in non-treated conditions. Further analysis showed that adsorptive detoxification was not the controlling factor for enhanced ethanol production under stress conditions, attributed to its low removal of furfural (< 20%) and incapability of acetic acid removal. When biochar was filtered from the biochar-treated inhibitor-containing broth, it still showed enhanced ethanol production. Furthermore, Z. mobilis immobilized on biochar was also observed. Thus, biochar extracts in the fermentation broth and cell immobilization on biochar might be the controlling factors for enhanced ethanol production under stress conditions.ConclusionsThese results indicate that biochar-mediated enhanced ethanol fermentation (BMEEF) might be a promising strategy for ethanol production from lignocellulosic biomass.

A Miracle Metal@Zeolite for Selective Conversion of Syngas to Ethanol

Direct catalytic conversion of syngas provides a desirable route for ethanol manufacture; however, it still suffers from poor ethanol selectivity and insufficient catalyst durability. In this issue of Chem, Wang et al. design a catalyst with a metal@zeolite core-shell structure, enabling remarkably high ethanol production from syngas with long-term stability.

Hierarchically porous Cu/Zn bimetallic catalysts for highly selective CO2 electroreduction to liquid C2 products

Hierarchically macroporous-mesoporous (HMMP) Cu/Zn alloy catalysts are reported to promote CO2 electroreduction towards liquid C2 products. HMMP Cu/Zn alloys with two types of distinct pores (∼320 nm and ∼20 nm) and adjustable alloy compositions are prepared through the interfacial self-assembly of two polymer templates and metal precursors. Due to add-in synergies of hierarchically porous structures and bimetallic elemental compositions, the resultant HMMP Cu/Zn alloy catalysts remarkably promote the deep electroreduction of CO2 to liquid C2 products while simultaneously suppressing the competitive proton reduction. Among them, HMMP Cu5Zn8 exhibits the best electrocatalytic selectivity (with a very high ethanol production of 46.6 % at −0.8 V) and excellent stability (even after electrocatalysis for 11 h) towards CO2 electroreduction. This strategy allows for the reliable synthesis of other HMMP alloy nanocatalysts for a wide range of electrocatalytic applications.

Microwave-assisted pretreatment using alkali metal salt in combination with orthophosphoric acid for generation of enhanced sugar and bioethanol

The microwave-assisted alkali salt (NaCl, MgCl2, and KCl) in combination with H3PO4 pretreatment of rice straw followed by enzymatic hydrolysis with in-house and commercial enzyme cocktail (cellulase and xylanase) was investigated. The effect of pretreatment on the structure and composition of RS was investigated using XRD and FTIR analysis, and the result suggested strategic structural changes in the RS structure. The maximum CrI of 51.3% was obtained with KCl–H3PO4 pretreatment system which is in line with maximum saccharification per biomass of 79% using commercial xylanase and cellulase enzyme cocktail (ComCK–XylCell). Comparable saccharification per biomass of 74% was obtained with in-house xylanase and cellulase enzyme cocktail (CrCK–XylCell). The simultaneous saccharification and fermentation by KCl–H3PO4 pretreated system of RS resulted the maximum sugar yield of 30.6 and 26.9% and ethanol yield of 12.2 and 11.9 g/L using ComCK–XylCell and CrCK–XylCell cocktail, respectively, along with Saccharomyces cerevisiae MTCC 173. The hydrolysis of pretreated RS pulp using in-house enzyme cocktail resulted in high sugar and ethanol yield suggesting that the studied alkali metal in combination with weak acid such as H3PO4 can serve as a cost-effective and environment friendly pretreatment method for high production of sugar and ethanol.

Simultaneous vinegar fermentation from a pineapple by-product using the co-inoculation of yeast and thermotolerant acetic acid bacteria and their physiochemical properties.

In the present study, a potential newly isolated thermotolerant acetic acid bacteria (TH-AAB), Acetobacter pasteurianus FPB2-3, with ethanol and acetic acid-tolerant properties was found to be very effective in the production of vinegar from pineapple peels as an alternative, inexpensive raw material using simultaneous vinegar fermentation (SVF). The results showed that using whole pineapple peel with the addition of diammonium phosphate (DAP) and MgSO4 at an initial pH of 5.5 gave a slightly higher acetic acid content than that produced from the squeezed juice. Subsequently, the effects of sugar concentration and inoculation time of A. pasteurianus FPB2-3 on acetic acid production were examined. The results revealed that an increase in sucrose concentration led to the high production of ethanol, which resulted in the suppression of acetic acid production. Allowing for the inoculated yeast to ferment prior to inoculation of the AAB for 1 or 2days resulted in a longer lag time for ethanol oxidation. However, acetic acid accumulation commenced after 5days and gradually increased to the maximum concentration of 7.2% (w/v) within 16days. Furthermore, scaled-up fermentation in 6l vessels resulted in slower acetic acid accumulation but still achieved a maximum acetic acid concentration of up to 6.5% (w/v) after 25days. Furthermore, the antioxidant capacity of the vinegar produced from pineapple peels (PPV) was slightly higher than that produced from the squeezed juice (PJV), which was consistent with the higher total phenolic compound content found in the PPV sample. In addition to acetic acid, a main volatile acid present in vinegars, other volatile compounds, such as alcohols (isobutyl alcohol, isoamyl alcohol, and 2-phenyl ethanol), acids (3-methyl-butanoic acid), and esters (ethyl acetate, 3-methyl butanol acetate, and 2-phenylethyl acetate), were also detected and might have contributed to the observed differences in the odour and aroma of the pineapple vinegars.

Fibrillating wood chips to facilitate high-valued lignin extraction and high titer ethanol production

In this study, a physical-chemical pretreatment strategy, using a twin-screw extrusion process for wood chips micro-fibrillation and subsequent chemical pretreatment with a recyclable acid hydrotrope, was developed to facilitate the extraction of high-valued lignin and the enzymatical hydrolysis of cellulose. At an optimum pretreatment severity of T70C70, the fibrillated wood chips were dissolved for approximately 89 % with a negligible loss of cellulose and considerable removals of lignin and hemicellulose (45 % and 65 %, respectively). The obtained lignin exhibited excellent structural profiles, such as high hydroxyl content (aliphatic OH of 2.31 mmol/g), more β-O-4 aryl ether linkages (59.05 %), low Mw (3736 g/mol), and narrow polydispersity (Mw/Mn, 2.03), according the characterization results from FTIR, TGA, GPC, 31P NMR, and 2D HSQC NMR measurements. The residual glucan-rich solid was enzymatically hydrolyzed for high titer ethanol production via a Q-SSF process, resulting in a high ethanol concentration of 47.62 g/L.

BIOETHANOL PRODUCTION FROM APPLE POMACE USING CO-CULTURES WITH SACCHAROMYCES CEREVISIAE IN SOLID-STATE FERMENTATION

The objective of this study was isolation and screening of apple pomace utilizing microorganisms from soil which can be used as co-culture with S. cerevisiae for production of bioethanol. In this study, fifteen microorganisms were isolated from soil near the dumping site of apple pomace at HPMC, Parwanoo, H.P. on medium enriched with apple pomace. These isolates were assigned codes APW 1-15 and were screened for their potential to produce cellulase, xylanase and ethanol. The selected isolates were used as co-culture with S. cerevisiae for bioethanol production. All the isolates exhibited cellulase and xylanase activities ranging from 228.2 to 502.5 U/mL/min and 185.3 to 1010.7 U/mL/min respectively, but only three isolates (APW-02, APW-04 and APW-12) produced ethanol. Isolate APW-13 exhibited highest cellulase activity (502.5 U/mL/min), APW-04 showed highest xylanase activity (1010.7 U/mL/min) and APW-12 produced highest amount of ethanol (36 g/L). Two isolates (APW-12 and APW-13) were selected to co-culture with S. cerevisiae in solid-state fermentation of apple pomace for ethanol production. S. cerevisiae and isolate APW-12 co-culture fermentation resulted in higher ethanol production (49.64 g/L) than S. cerevisiae and APW-13 co-culture fermentation (41.7 g/L) while, S. cerevisiae alone produced 37.6 g/L ethanol. Isolate APW-12 and APW-13 belonged to genera Actinomyces and Bacillus respectively.

Assessment of microbial quality and health risks associated with traditional rice wine starter Xaj-pitha of Assam, India: a step towards defined and controlled fermentation.

This study reports the microbial quality of ethnic starter culture Xaj-pitha used for rice wine fermentation in Assam. Here, we collected 60 Xaj-pitha samples belonging to Ahom community of the state and enumerated the microorganisms using spread plate technique. Illumina-based whole genome shotgun sequencing detected the presence of microbial contaminants like Acidovorax, Herbaspirillum, Methylobacterium, Pantoea, Pseudomonas, Stenotrophomonas, Staphylococcus, Micrococcus, Acinetobacter, etc. Presence of major health hazards associated with spontaneous rice wine fermentation necessitated method optimization through the development of a defined mixed starter culture. For this, functionally important α-amylase producers viz., Penicillium sp. ABTSJ23, Rhizopus oryzae ABTSJ63, Mucor guilliermondii ABTSJ72 and Amylomyces rouxii ABTSJ82 and eight yeasts viz., Saccharomyces cerevisiae ABTY1J, ABTY1S, ADJ5 & ADJ1,Wickerhamomyces anomalus ADJ2, Saccharomycopsis malanga ADJ3, Saccharomycopsis fibuligera ADJ4 and Saccharomycopsis malanga ADJ6 were retrieved using appropriate media. All the mould cultures tested negative for aflotoxins production. Among the yeasts, Saccharomyces cerevisiae ABTY1S and ADJ1 decarboxylated lysine HCl and tyramine HCl, respectively, indicating their biogenic amine production ability. For defined mixed starter culture, Amylomyces rouxii ABT82 with α-amylase (5.92U/ml) and glucoamylase (7.50U/ml) activities was selected as fungal partner; while Saccharomycopsis fibuligera ADJ4 and Saccharomyces cerevisiae ABT-Y1J with high ethanol production (up to 10.11% and 9.88% v/v, respectively) were selected as yeast partners. The mixed culture was able to produce high amount of glucose, ethanol and liquid (glucose 10.91% w/v; ethanol 7.5% w/v; liquid 51.0% w/v). Therefore, this study demonstrated the efficiency of mixed starter cultures for safe and controlled rice wine production.

Correlation between Ethanol Productivity and Biomass Formation from Sugarcane Juice Industrial Wastes by Genetically Recombinant Saccharomyces Cerevisiae

Sugarcane juice sub- products was the main source of carbohydrates for ethanol productivity and biomass formation . It contains sugars as a good alternative material for ethanol production from yeast to meet the large scale consumption of petroleum fuels . Therefore, the main objective of this study was undertaken to determine the correlation between ethanol productivity and biomass formation using different concentrations of sugarcane juice industrial by - products as a main source of carbon .15 hybrids of Saccharomyces cerevisiae derived from three crosses conducted between five parental strains were used in this study . The results of fermentation process on bioethanol production were graphically diagrammatic. The data showed in most cases negative correlations between ethanol production and biomass formation as shown from genotypes of crosses P1 x P4 and P3 x P5 . This indicated that high productivity of ethanol was associated with a lower biomass formation due to ethanol toxicity on the viability of yeast cells . On the contrary , genotypes resulted from cross between P2 x P5 showed positive correlation between both parameters at 0.02 and 0.06 g of sugarcane juice sub - products . Therefore, it is possible that genotypes derived from this cross may be more tolerant to ethanol inhibitor. In addition , the greater use of sugars for growing yeast cells resulting in a lower ethanol productivity and vice – versa . The results indicated that genome shuffling via hybridization is a powerful tool for inducing genetic recombinants in yeast for desirable industrial phenotypes.

Effect of Myclobutanil Pesticide on the Physiological Behavior of Two Newly Isolated Saccharomyces cerevisiae Strains during Very-High-Gravity Alcoholic Fermentation.

Yeasts are able to act as biosorbents, as their cell wall includes several components capable of binding organic xenobiotic compounds that can potentially be removed during various fermentation processes. In the present investigation, two novel Saccharomyces cerevisiae strains (LMBF-Y 16 and LMBF-Y-18), previously isolated from grapes, were studied regarding their physiological behavior (dry cell weight—DCW production, substrate uptake, and ethanol and glycerol biosynthesis) during fermentations of grape must, in some cases enriched with commercial glucose and fructose (initial total sugar concentration approximately 150 and 250 g/L, respectively). Myclobutanil (a chiral triazole fungicide broadly used as a protective agent of vine) was also added to the culture media at various concentrations in order to assess the ability of the yeasts to simultaneously perform alcoholic fermentations and detoxify the medium (i.e., to remove the fungicide). In the first set of experiments and for both tested strains, trials were carried out in either 250 mL or 2.0 L agitated shake flasks in either synthetic glucose-based experiments or grape musts. Since the results obtained in the trials where the cultures were placed in 2.0 L flasks with grape musts as substrates were superior in terms of both DCW and ethanol production, these experimental conditions were selected for the subsequent studies. Both strains showed high fermentative efficiency, producing high amounts of DCW (9.5–10.5 g/L) in parallel with high ethanol production, which in some cases achieved values very close to the maximum theoretical ethanol production yield (≈0.49 g of ethanol per g of sugar). When using grape must with initial total sugars at approximately 250 g/L (very high gravity fermentation media, close to winemaking conditions), significantly high ethanol quantities (i.e., ranging between 105 and 123 g/L) were produced. Myclobutanil addition slightly negatively affected sugar conversion into ethanol; however, in all cases, ethanol production was very satisfactory. A non-negligible myclobutanil removal during fermentation, which ranged between 5%–27%, as a result of the adsorptive or degradative capacity of the yeast was also reported. The presence of myclobutanil had no effect on DCW production and resulted in no significant differences in the biosynthesis of glycerol. Therefore, these newly isolated yeast strains could be excellent candidates for simultaneous high ethanol production and parallel pesticide removal in a general biorefinery concept demonstrating many environmental benefits.

Selection of yeasts from bee products for alcoholic beverage production.

The use of appropriate yeast strains allows to better control the fermentation during beverage production. Bee products, especially of stingless bees, are poorly explored as sources of fermenting microorganisms. In this work, yeasts were isolated from honey and pollen from Tetragonisca angustula (Jataí), Nannotrigona testaceicornis (Iraí), Frieseomelitta varia (Marmelada), and honey of Apis mellifera bees and screened according to morphology, growth, and alcohol production. Bee products showed to be potential sources of fermenting microorganisms. From 55 isolates, one was identified as Papiliotrema flavescens, two Rhodotorula mucilaginosa, five Saccharomyces cerevisiae, and nine Starmerella meliponinorum. The S. cerevisiae strains were able to produce ethanol and glycerol at pH 4.0-8.0 and temperature of 10-30 °C, with low or none production of undesirable compounds, such as acetic acid and methanol. These strains are suitable for the production of bioethanol and alcoholic beverages due to their high ethanol production, similar or superior to the commercial strain, and in a broad range of conditions like as 50% (m/v) glucose, 10% (v/v) ethanol, or 500 mg L-1 of sodium metabisulfite.

Physiological effects of overexpressed sigma factors on fermentative stress response of Zymomonas mobilis

Zymomonas mobilis is a bacterium of industrial interest due to its high ethanol productivity and high tolerance to stresses. Although the physiological parameters of fermentation are well characterized, there are few studies on the molecular mechanisms that regulate the response to fermentative stress. Z. mobilis ZM4 presents five different sigma factors identified in the genome annotation, but the absence of sigma 38 leads to the questioning of which sigma factors are responsible for its mechanism of fermentative stress response. Thus, in this study, factors sigma 32 and sigma 24, traditionally related to heat shock, were tested for their influence on the response to osmotic and ethanol stress. The overexpression of these sigma factors in Z. mobilis ZM4 strain confirmed that both are associated with heat shock response, as described in other bacteria. Moreover, sigma 32 has also a role in the adaptation to osmotic stress, increasing both growth rate and glucose influx rate. The same strain that overexpresses sigma 32 also showed a decrease in ethanol tolerance, suggesting an antagonism between these two mechanisms. It was not possible to conclude if sigma 24 really affects ethanol tolerance in Z. mobilis, but the overexpression of this sigma factor led to a decrease in ethanol productivity.

The active site of syngas conversion into ethanol over Cu/ZnO/Al2O3 ternary catalysts in slurry bed

As a promising technology, selective conversion of syngas to ethanol over the CuZnAl catalyst has a long-standing interest in current energy research. Here, we report cooperative ZnO and Al2O3 clusters on the Cu(1 1 1) surface for selective hydrogenation of CO to ethanol using density functional theory (DFT) and microkinetic model. Our results show that the Cu-ZnO synergy facilitates CO initial activation to CHO, the cooperation of the three components is necessary for CH3 formation via the direct dissociation of the formed CH3OH that is the rate-controlling step throughout the whole process, and the aid of the Cu-Al2O3 synergy is indispensable for the initial carbon chain formation by CO insertion into CH3 intermediate with a 0.45 activation barrier. Apart from the ethanol synthesis, we propose the possibility of syngas conversion into ethylene glycol that is a typical atom economic reaction. Moreover, thermodynamic and kinetic barriers and charge analyses results identify that the carbon chain growth via CHO coupling with the assistant of Cu-ZnO synergy is facile for the formation of ethylene glycol. In order to achieve high ethanol productivity and selectivity over the CuZnAl catalyst, the aid of a metal promoter with the function of facilitating the CHO hydrogenation and/or suppressing the CHO coupling is required. This work not only clarifies the synergy of Cu, ZnO, and Al2O3 components of CuZnAl catalyst for ethanol synthesis, but also offers an alternative nonpetroleum route for the ethylene glycol synthesis.

Syngas-aided anaerobic fermentation for medium-chain carboxylate and alcohol production: the case for microbial communities.

Syngas fermentation has been successfully implemented in commercial-scale plants and can enable the biochemical conversion of the driest fractions of biomass through synthesis gas (H2, CO2, and CO). The process relies on optimized acetogenic strains able to reach and maintain high productivity of ethanol and acetate. In parallel, microbial communities have shown to be the best choice for the production of valuable medium-chain carboxylates through anaerobic fermentation of biomass, demanding low technical complexity and being able to realize simultaneous hydrolysis of the substrate. Each of the two technologies benefits from different strong points and has different challenges to overcome. This review discusses the rationales for merging these two seemingly disparate technologies by analyzing previous studies and drawing opinions based on the lessons learned from such studies. For keeping the technical demands of the resulting process low, a case is built for using microbial communities instead of pure strains. For that to occur, a shift from conventional syngas-based to "syngas-aided" anaerobic fermentation is suggested. Strategies for tackling the intricacies of working simultaneously with communities and syngas, such as competing pathways, and thermodynamic aspects are discussed as well as the stoichiometry and economic feasibility of the concept. Overall, syngas-aided anaerobic fermentation seems to be a promising concept for the biorefinery of the future. However, the effects of process parameters on microbial interactions have to be understood in greater detail, in order to achieve and sustain feasible medium-chain carboxylate and alcohol productivity.

Rheological characteristics and genotype correlation of cassava root for very high gravity ethanol production: The influence of cassava varieties and harvest times.

In very high gravity (VHG) ethanol fermentation, the rheological properties of native cassava significantly influence heat and mass transfer, mixing energy, and, thus, the yield of all steps. This study investigated the effect of cassava varieties and their harvest times on starch liquefaction, saccharification, and fermentation. The genotype correlation of the starch properties was revealed for the most suitable cassava varieties. First, the starch content, amylose content, total reducing sugar from liquefaction and saccharification, pasting properties, and ethanol yields of six cassava varieties (Huay Bong 60, Hanatee, Kasetsart 50, Pirun 1, Pirun 2, and Rayong 11) at 6-, 9-, 12-, and 15-month harvest times were evaluated. The amylose content increased significantly from the 6th to the 12th month but slightly decreased at the 15th month. It was observed that the starch content contributed to a more substantial influence on the change in peak viscosity than on the amylose content. Ethanol fermentation using Saccharomyces cerevisiae TISTR5606 showed that the Rayong 11 variety at the 15-month harvest time provided the highest ethanol concentration of 104.7±4.1gL-1 and an ethanol yield of 0.4±0.1gethanolg-1 reducing sugar, which corresponded to 74.5% of the theoretical yield.