Co-production Of Ethanol Research Articles

Standardized amino acid digestibility and true metabolizable energy for several increased protein ethanol co-products produced using back-end fractionation systems

Precision-fed rooster trials were conducted to evaluate standardized AA digestibility and TMEn of the increased protein ethanol co-products corn fermented protein (CFP), high protein-distillers dried grains with solubles (HP-DDGS), and reduced fiber high protein-DDGS (RFHP-DDGS) produced using post-fermentation back-end fractionation systems. The TMEn was determined using conventional adult Leghorn roosters, while cecectomized roosters were used to determine standardized AA digestibility. Three to 6 roosters were fasted per treatment for 26 h prior to crop intubation with 27 g of sample and excreta were collected for 48 h post-feeding. Statistical analyses were conducted using a one-way ANOVA for a completely randomized design. Eight samples of CFP were found to contain a mean of 56% CP (DM basis) compared with a mean of 32% for conventional DDGS. The mean TMEn of CFP (3,556 kcal/kg) was greater (P < 0.05) than conventional DDGS1 and 2 (2,767 kcal/kg DM); mean standardized AA digestibility for CFP was similar to conventional DDGS and ranged from 88 to 94%. The mean digestible Lys, Met+Cys, and Thr concentrations for conventional DDGS were 0.79, 1.12, and 0.94%, respectively, whereas those for CFP were 1.74, 2.06, and 1.88%, respectively (DM basis). Two samples of HP-DDGS contained a mean of 51% CP (DM basis), a mean TMEn of 3,325 kcal/kg DM, a mean standardized AA digestibility of 90%, and mean concentrations of digestible Lys, Met+Cys, and Thr, which were 1.53, 1.77, and 1.60%, respectively (DM basis). The mean CP content of 2 RFHP-DDGS was 48% and the mean TMEn was 3,711 kcal/kg DM, which was greater (P < 0.05) than conventional DDGS3 and 4 (2,920 kcal/kg DM). Mean standardized AA digestibility of RFHP-DDGS was 90% and mean digestible Lys, Met+Cys, and Thr concentrations increased from 0.82, 1.01, and 0.95% for conventional DDGS, respectively, to 1.00, 1.59, and 1.44% for RFHP-DDGS, respectively (DM basis). Results indicate these high protein corn ethanol co-products have increased nutritional value for poultry compared with conventional DDGS.

Preparation of nanocellulose crystal from bleached pulp with an engineering cellulase and co-production of ethanol

The study investigated the feasibility of co-production of nanocellulose crystal (CNC) and ethanol using the bleached pine kraft pulp (BPKP) as a substrate by enzymatic hydrolysis. An engineering strain Penicillum oxalicum cEES-XM was constructed to produce suitable cellulase used in enzymatic hydrolysis of BPKP for preparing CNC. The cellulase from Trichoderma reesei SCB18 was used for simultaneous saccharification and fermentation of residues and hydrolysates from enzymatic hydrolysis for producing ethanol. The result showed that the CNC yield reached 7.35 % (w/w) by hydrolysis at 10 % solid content, and the final ethanol concentration was 13.27 mg/mL in fermentation liquor. Using SEM, XRD, TGA, and DLS methods, the characteristics of CNC including, morphology, crystallinity, thermal stability and particle size distribution, were also examined. This work provided a reference for realizing high-efficient application of cellulose in the pulp.

A sustainable process for co-production of xylooligosaccharides and ethanol from alkali treated sugarcane bagasse: A strategy towards waste management

Present study aims at sustainable utilization of sugarcane bagasse (SCB) for production of valuable prebiotic xylooligosaccharides (XOS) along with second generation ethanol. Fractionation of SCB into hemicellulose rich liquid fraction and cellulose rich solid residue was achieved using alkaline treatment. Carbohydrate rich precipitate obtained from liquid fraction was utilized for XOS production using inhouse produced endoxylanase. XOS production from SCB xylan was optimized by employing response surface methodology. Under optimized conditions, maximum XOS yield was 227.72 mg/g of carbohydrate rich precipitates. The solid residue obtained after alkaline pretreatment was used for ethanol fermentation by prehydrolysis and simultaneous saccharification and fermentation (P-SSF) process using cellulolytic enzyme cocktail and Saccharomyces cerevisiae SM1. Maximum ethanol concentration, productivity and yield were 79.76 ± 0.16 g/L, 0.83 g/L/h and 69.38%, respectively by employing P-SSF process. Based on the experimental data it can be predicted that bioconversion of 100 g raw SCB can yield 6.26 g of XOS (DP 2-DP 5), 15.95 g ethanol and 1.44 g of xylitol. Present investigation reports an integrated process for effective bioconversion of SCB into value added products by maximum utilization of cellulosic and hemicellulosic fractions simultaneously using indigenously produced fungal enzymes.

Improved energy efficiency in microbial fuel cells by bioethanol and electricity co-generation

BackgroundMicrobial electricity production has received considerable attention from researchers due to its environmental friendliness and low price. The increase in the number of intracellular electrons in a microbial fuel cell (MFC) helps to improve the MFC performance.ResultsIn this study, we accumulated excess electrons intracellularly by knocking out the gene related to intracellular electron consumption in Saccharomyces cerevisiae, and the elevated intracellular electron pool positively influenced the performances of MFCs in terms of electricity production, while helping to increase ethanol production and achieve ethanol and electricity co-production, which in turn improved the utilization of substrates. The final knockout strain reached a maximum ethanol yield of 7.71 g/L and a maximum power density of 240 mW/m2 in the MFC, which was 12 times higher than that of the control bacteria, with a 17.3% increase in energy utilization.ConclusionsThe knockdown of intracellular electron-consuming genes reported here allowed the accumulation of excess electrons in cells, and the elevated intracellular electron pool positively influenced the electrical production performance of the MFC. Furthermore, by knocking out the intracellular metabolic pathway, the yield of ethanol could be increased, and co-production of ethanol and electricity could be achieved. Thus, the MFC improved the utilization of the substrate.

Co-production of xylose, lignin, and ethanol from eucalyptus through a choline chloride-formic acid pretreatment

A choline chloride-formic acid (ChCl-FA) pretreatment followed by enzymatic hydrolysis and fermentation were developed in this work for co-produce bioethanol, xylose, and lignin from eucalyptus. Results showed that ChCl-FA pretreatment can simultaneously degrade the xylan (∼95.2%) and lignin (∼74.4%) in eucalyptus, and obtained the pretreated eucalyptus having high glucan content and a numbers of cracks and holes, which was conducive to follow-up cellulase attacking. The hydrolysis experiments showed the maximum yield of glucose of 100 g eucalyptus was 35.3 g, which was equivalent to 90.3% of glucan in eucalyptus feedstock. The fermentation of enzymatic hydrolysate finally achieved the ethanol yield of 16.5 g, which corresponded to 74.5% theoretical ethanol yield from initial glucan in eucalyptus. In addition, 12.1 g xylose and 23.9 g lignin also could be obtained in pretreated liquid or/and hydrolysis residue, which represented for 61.4% xylan and 80.7% lignin in eucalyptus feedstock, respectively.

Coproduction of hydrogen, butanol, butanediol, ethanol, and biogas from the organic fraction of municipal solid waste using bacterial cocultivation followed by anaerobic digestion

An integrated bioprocessing approach was applied to enhance energy recovery from the biodegradable fraction of municipal solid waste (BFMSW). Clostridium acetobutylicum and Enterobacter aerogenes with complementary characteristics were cocultivated for coproduction of hydrogen, 2,3-butanediol, and acetone-butanol-ethanol (ABE). Following the fermentation process, the remaining solids were used for biomethane production. The BFMSW was first subjected to ethanolic organosolv pretreatment and then enzymatic cellulose and hemicellulose hydrolysis at 5 and 8% solid loadings. The glucose (328 g/kg raw BFMSW), xylose (37.8 g/kg raw BFMSW), and starch (152.1 g/kg raw BFMSW) portions of the pretreated BFMSW hydrolysate with 5% solid loading were cofermented to hydrogen (162.8 L/kg raw BFMSW), 2,3-butanediol (42.5 g/kg raw BFMSW), butanol (121.9 g/kg raw BFMSW), ethanol (38.9 g/kg raw BFMSW), and acetone (45.2 g/kg raw BFMSW) by the coculture, and subsequently, the residual unfermented solids were further digested to biomethane (31.7 L/kg raw BFMSW). From the bioenergy perspective, 311.8 mL gasoline equivalent (10 MJ energy) was obtained from each kg of raw BFMSW, indicating the potential of the integrated fermentation-anaerobic digestion bioprocess for biofuels production from the zero-cost substrate.

Integrated production of ethanol and xylitol from Brassica juncea using Candida sojae JCM 1644

The present study demonstrates a novel strategy involving two-step fermentation of lignocellulosic hydrolysate for the integrated production of ethanol and xylitol using a newly isolated yeast strain, Candida sojae JCM 1644. The isolated strain was characterised by its carbohydrate assimilation efficiency and tolerance towards inhibitors generated during pretreatment and fermentation of lignocellulosic biomass. In brief, the study comprised alkali treatment of Brassica juncea followed by its saccharification with cellulase consortia. An isolated strain was used for the co-production of xylitol and ethanol from sugar hydrolysate, and several parameters were systematically optimised for maximum co-production of ethanol and xylitol. Out of total glucose (149.72 g/L) and xylose (84.21 g/L) present in biomass hydrolysate, a product yield of 0.45 g/g (ethanol) and 0.62 g/g (xylitol) was achieved for a two-step fermentation process, which was 15.57% and 11.78% higher than the yield achieved for ethanol and xylitol, respectively, in a one-step fermentation process.

Volumetric Scale-Up of a Packed-Bed Ion-Exchange System to Extract Phytate from Thin Stillage.

Phytate is the main form of phosphorus in corn ethanol coproducts and poses digestion issues in monogastric-animal feed. Extracting phytate as a commodity chemical will bring extra revenue to the corn ethanol industry and reduces potential phosphorus pollution from livestock waste management. We assessed a simplified scale-up approach of an ion-exchange separation system applied to extract phytate from thin stillage using volumetric parameters and simplifications of the van Deemter model. Thin stillage is one of the main byproducts generated on dry-grind corn-to-ethanol plants and accounts for the liquid portion of the bottom product generated in the ethanol distillation process. Thin stillage is rich in dissolved phytate, which served as the basis for an ion-exchange extraction system developed with a scalability factor of 50. Under the evaluated conditions, similar breakthrough profiles were obtained when similar Péclet and Stanton numbers were maintained for the scales studied, demonstrating that a simple and straightforward scale-up can be attained if special attention is given to maintaining both parameters as the basis of calculations of the plate numbers of ion-exchange columns.

Efficient coproduction of butanol, ethanol, and biohydrogen from municipal solid waste through a cocultivated biorefinery

The cocultivation of Clostridium acetobutylicum and Mucor indicus was evaluated for the first time to take the advantages of both microorganisms for fully exploiting the energy potential of the organic fraction of municipal solid waste (OFMSW), generating high yields of acetone-butanol-ethanol (ABE) and hydrogen through a biorefinery scheme. Unlike M. indicus, C. acetobutylicum can ferment unhydrolyzed starch and pentose sugars. However, the low biofuel titer through ABE fermentation makes the bioprocess uneconomical. The fungal-bacterial symbiosis led to high ethanol titer along with high butanol and hydrogen yields without the need for starch hydrolysis. The effects of most influencing factors, i.e., initial pH, bacterium to fungus biomass ratio, and solid loading, on ABE and hydrogen production were investigated. The fermentation of organosolv pretreated OFMSW hydrolysate at initial pH of 5.5 and solid loading of 5% with 1:1 bacterium to fungus biomass ratio produced 80.2 g butanol, 30.2 g acetone, 108.1 g ethanol, and 96.3 L hydrogen from each kg raw OFMSW. From the bioenergy point of view, 7.2 MJ energy was generated, which was significantly higher than those obtained via the mono cultivation of C. acetobutylicum (6.2 MJ) and M. indicus (4.4 MJ), indicating the great potential of the fungal-bacterial cocultivation for bioenergy production from OFMSW. The economic potential of the cocultivated biorefinery was 0.16 $/kg OFMSW.

Biorefinery potential of newly isolated yeast Clavispora lusitaniae for co-production of erythritol and ethanol

Biorefinery potential of newly isolated yeast Clavispora lusitaniae for co-production of erythritol and ethanol

Toward an Understanding of Physical and Biological Properties of Corn-Based Whole Stillage, Thin Stillage, and Condensed Distillers Solubles and Changes Thereof During Storage

The production of bio-based ethanol has been one of the fastest growing industries in the United States during the past decade. Thus, wider exploration of ethanol coproduct uses is necessary in the ethanol plant. Currently, process steams such as whole stillage, thin stillage, and syrup are processed into distiller dried grains with solubles and fed to livestock. The storability of whole stillage, thin stillage, and syrup influences the economic and energetic balances of fuel ethanol production. However, there are few investigations of the shelf life for these products or how to measure these quantities. The objectives of this research were to test physical and biological properties of whole stillage, thin stillage, and syrup and determine storability and allowable shelf life for these materials as influenced by storage temperature levels. Using standard laboratory methods, several properties were determined, including moisture content, water activity, thermal properties (conductivity, resistivity, volumetric heat capacity, and diffusivity), color, mold development, and CO2 production. Also, the separation processes due to settling were observed over 72 h. The thin stillage and whole stillage had relative high average moisture contents of 92% (w.b.) and 87% (w.b.), respectively, and a mean water activity of 0.99; the high water content marked samples easily susceptible to rapid spoilage. Time had a significant effect (p &amp;lt; 0.05) on properties of coproducts. Both thin stillage and whole stillage samples got mold growth after 5 days incubation at 32°C. Thin stillage had the greatest separation rate in the settling experiment. However, syrup had a relative low average moisture content of 62% and an average water activity of 0.92. No mold growth and settling separation happened in syrup samples. There was no evidence showing that a linear relationship exists between Hunter L*, a* and b*, and mold growth. The Solvita® test showed that high-temperature treatment caused high CO2 production in all samples. The exponential models described the relationship between storage time (from 0 to 5 days at 25 and 35°C) and CO2 concentration for the three coproducts. This study is a first step to explore opportunities for utilizing valuable components from these coproducts. Follow-up study should work on separation processes to concentrate the valuable components of these coproducts. Exploring the potential value of ethanol coproducts could maintain and improve the profitability of the ethanol industry.

Hydrothermal co-hydrolysis of corncob/sugarcane bagasse/Broussonetia papyrifera blends: Kinetics, thermodynamics and fermentation

Biorefinery of biomass blends can achieve sustainable development of biofuel production. Herein, three lignocellulosic wastes with significant differences in chemical composition—namely corncob (CC), sugarcane bagasse (SB), and Broussonetia papyrifera (BP)—were selected to investigate their hydrothermal co-hydrolysis kinetics and thermodynamics of different biomass blends. Activation energies of hemicellulose decomposition (Ea1, 90.59 kJ/mol) for CC/SB were lower than those for CC (126.12 kJ/mol) and CC/SB/BP (153.62 kJ/mol). BP (having a high content of nitrogen sources) loading weakened the acidic autohydrolysis of CC/SB hemicellulose, but yielded stable products as indicated by the negative entropy value for CC/SB/BP hydrolysis. Cumulative feedback inhibition occurred among different biomass, and it could be minimized by controlling the blending ratio. The highest total xylose yield was 83.64% for CC/SB with a mass ratio of 2:1. Moreover, biomass blend of CC/SB/BP enabled complete utilization of hexose, pentose and amino acids by co-production of ethanol and microalga biomass.

Techno‐economics of one‐stage and two‐stage furfural production integrated with ethanol co‐production from sugarcane lignocelluloses

AbstractLignocellulosic biomass processing to produce platform chemicals and biofuels is a promising alternative utilization of non‐renewable resources. This study investigated the techno‐economics of two‐stage and one‐stage furfural production integrated with ethanol co‐production from sugarcane bagasse and harvest residues. The effect of process conditions on profitability was reflected by the minimum ethanol selling price (MESP) at a fixed furfural‐selling price. Aspen Plus V8.8 was used to simulate the integrated two‐stage furfural and ethanol co‐production biorefineries using low (scenario 1), medium (scenario 2) and high (scenario 3) severity steam‐explosion pretreatment. The two‐stage furfural biorefineries integrated with ethanol co‐production were compared with the most profitable one‐stage furfural biorefinery integrated with ethanol co‐production. The required MESP in scenario 2 (0.73 US$ L–1) was decreased by 36% compared with the one‐stage furfural‐ethanol biorefinery (1.14 US$ L–1). Scenarios 1 and 3 were disadvantaged by lower ethanol yields (150 versus 214 kg t–1 of feed) and higher capital investments (322–340) compared with scenario 2 (310 million US$). The one‐stage furfural production had higher heating demands (2034 versus 741–1124 kW t–1 feed) and reduced ethanol yields (90 versus 150–214 kg t–1 of feed) compared with integrated two‐stage furfural and ethanol coproduction biorefineries. Optimization of process conditions, improving energy efficiency, and maximizing productivity within these energy self‐sufficient facilities were critical to minimizing the MESPs, regardless of associated increases in capital and operational costs. © 2021 Society of Chemical Industry and John Wiley &amp; Sons, Ltd

Electro-fermentation enhances H2 and ethanol co-production by regulating electron transfer and substrate transmembrane transport

Electro-fermentation systems (EFSs) are an emerging technology capable of regulating microbial fermentation pathways by tuning oxidation-reduction potentials and electron flow. However, there is limited understanding of the bioenergy conversion and metabolic regulation of fermentative bacteria in EFSs. In this study, we investigated how electrode potentials in EFSs affect the metabolic products and global transcriptome expression of Ethanoligenens harbinense. The E. harbinense-inoculated anodic EFS (AEFS) with a poised potential of 0 V or the cathodic EFS (CEFS) with a poised potential of 0 V (vs. Ag/AgCl reference electrode) obtained the maximum H2 production of 1888–1986 mL/L-medium, which increased by 23–26% compared with open-circuit fermentation (OC-EFSs). The highest H2 yield of 1.190 ± 0.009–1.197 ± 0.001 mol-H2/mol-glucose was obtained by the AEFS0 and the OC-EFS. Ethanol production of AEFS-0.4 increased by 30.7 ± 13.3% compared with OC-EFSs. In addition, glucose uptake and cell growth in the EFS were enhanced with an increase in cellular energy supply. Transcriptome analysis revealed that overexpression of the [FeFe]-hydrogenase, ferredoxin, and rubredoxin genes in the AEFS with a poised potential of 0 V promoted the H2 production rate. Genes involved in electron transfer and reduced nicotinamide adenine dinucleotide (NADH) regeneration were upregulated in the AEFS, leading to more ethanol production. In addition, substrate transmembrane transport was suppressed by underexpression of adenosine triphosphate (ATP)-binding cassette (ABC) transporter system-related genes at lower or higher potentials. These results confirm that an EFS effectively regulates the metabolite spectrum of H2-producing bacteria by coordinating electron transfer, NADH regeneration, and substrate transmembrane transport to provide a flexible approach for improving bioenergy production by fermentative bacteria.

Hybrid solar-seaweed biorefinery for co-production of biochemicals, biofuels, electricity, and water: Thermodynamics, life cycle assessment, and cost-benefit analysis

Combing solar energy with biomass processing facilities are emerging systems for efficient use of solar energy for electricity generation, energy storage, and production of renewable materials. In this work, we propose a novel combination of solar thermal energy systems with marine macroalgae biorefinery, which requires energy inputs for biomass cultivation and processing. In this work, we analyze a 10-ton dry weight per hour capacity pilot-scale hybrid solar seaweed biorefinery, located at the Mishor Rotem near Dimona, the current location for solar-thermal projects in Israel, where seaweed biomass supply comes from a hypothetical offshore farm located 15 km offshore. Our energy and mass balance analysis show that the overall First Law efficiency of the hybrid solar seaweed biorefinery system for the co-production of protein, hydrochar, ethanol, distilled water, and electricity is 32% and can exceed 40% with additional waste stream recycling. Our cost-benefit analysis of the proposed solar-seaweed biorefinery shows that the prices of seaweed, electricity, and protein are the key drivers of the profitability of the production process. The environmental impacts of the hybrid solar-seaweed biorefinery with intensified offshore cultivated biomass were quantified under various seaweed cultivation, transportation, and processing strategies.

Co-Production of Isobutanol and Ethanol from Prairie Grain Starch Using Engineered Saccharomyces cerevisiae

Isobutanol is an important and valuable platform chemical and an appealing biofuel that is compatible with contemporary combustion engines and existing fuel distribution infrastructure. The present study aimed to compare the potential of triticale, wheat and barley starch as feedstock for isobutanol production using an engineered strain of Saccharomyces cerevisiae. A simultaneous saccharification and fermentation (SSF) approach showed that all three starches were viable feedstock for co-production of isobutanol and ethanol and could produce titres similar to that produced using purified sugar as feedstock. A fed-batch process using triticale starch yielded 0.006 g isobutanol and 0.28 g ethanol/g starch. Additionally, it is demonstrated that Fusarium graminearum infected grain starch contaminated with mycotoxin can be used as an effective feedstock for isobutanol and ethanol co-production. These findings demonstrate the potential for triticale as a purpose grown energy crop and show that mycotoxin-contaminated grain starch can be used as feedstock for isobutanol biosynthesis, thus adding value to a grain that would otherwise be of limited use.

Assessment of Coproduction of Ethanol and Methane from Pennisetum purpureum: Effects of Pretreatment, Process Performance, and Mass Balance.

To overcome the structural complexity and improve the bioconversion efficiency of Pennisetum purpureum into bioethanol or/and biomethane, the effects of ensiling pretreatment, NaOH pretreatment, and their combination on digestion performance and mass flow were comparatively investigated. The coproduction of bioethanol and biomethane showed that 65.2 g of ethanol and 102.6 g of methane could be obtained from 1 kg of untreated Pennisetum purpureum, and pretreatment had significant impacts on the production; however, there is no significant difference between the results of NaOH pretreatment and ensiling-NaOH pretreatment in terms of production improvement. Among them, 1 kg of ensiling-NaOH treated Pennisetum purpureum could yield 269.4 g of ethanol and 144.5 g of methane, with a respective increase of 313.2% and 40.8% compared to that from the untreated sample; this corresponded to the final energy production of 14.5 MJ, with the energy conversion efficiency of 46.8%. In addition, for the ensiling-NaOH treated Pennisetum purpureum, the energy recovery from coproduction (process III) was 98.9% higher than that from enzymatic hydrolysis and fermentation only (process I) and 53.6% higher than that from anaerobic digestion only (process II). This indicated that coproduction of bioethanol and biomethane from Pennisetum purpureum after ensiling and NaOH pretreatment is an effective method to improve its conversion efficiency and energy output.

Co-production of hydrogen and ethanol by Thermoanaerobacterium thermosaccharolyticum KKU-ED1 from alpha-cellulose and cellulose fraction of sugarcane bagasse

This research aims to evaluate the co-production of hydrogen and ethanol from lignocellulosic materials by Thermoanaerobacterium thermosaccharolyticum KKU-ED1. The optimum conditions for co-production of hydrogen and ethanol in batch fermentation was determined using alpha-cellulose as a basic model substrate to mimic the natural cellulose part of a lignocellulosic material. The optimal conditions attained were an initial pH of 7.0, a temperature of 55 °C, and a cellulose content of 20 g/L, which resulted in the maximum hydrogen production and ethanol (EtOH) yield of 6113 mL H2/L and 1.71 mmol EtOH/g-celluloseconsumed, respectively. The potential of the KKU-ED1 strain to produce hydrogen and ethanol from natural cellulose in sugarcane bagasse was further evaluated under the optimum conditions. Hydrogen production and ethanol yield of 218 mL H2/L, and 0.26 mmol EtOH/g-celluloseconsumed were obtained. Results indicated that the strain KKU-ED1 is a thermophilic cellulolytic bacterium capable of co-producing hydrogen and ethanol from lignocellulosic materials.

Simulation of different biorefinery configuration including environmental, technical and economic assay using sugarcane bagasse

Due to growing environmental concerns mainly related to non-renewable fuels and high added-value chemicals, new solutions should reduce greenhouse gas emissions. Biorefineries, which use lignocellulosic biomass as raw material, emerges as a promising alternative to replace fossil fuels and to avoid competition between food and fuel production for arable land and drinking water. Sugarcane is one of the most harvested crops in the world, mainly in the equatorial zone. One tonne of processed cane generates between 300 and 400 kg of bagasse. This work proposes a biorefinery configuration for the co-production of ethanol, xylitol, lignin, and cellulose acetate, analyzing two different scenarios in the context of low sugarcane availability. The analysis included the determination of mass, total capital investment, total manufacturing costs, CO2 footprint, and water consumption. The cellulose acetate, ethanol, and xylitol production were economically viable only if lignin is considered a product. Positive net income, with return on investment in at least ten years, was achieved. Based on the environmental assessment, the carbon capture capacity is about 400 kg per tonne of sugarcane included in the process was determined.

2,3-Butanediol synthesis from glucose supplies NADH for elimination of toxic acetate produced during overflow metabolism

Overflow metabolism-caused acetate accumulation is a major problem that restricts industrial applications of various bacteria. 2,3-Butanediol (2,3-BD) synthesis in microorganisms is an ancient metabolic process with unidentified functions. We demonstrate here that acetate increases and then decreases during the growth of a bacterium Enterobacter cloacae subsp. dissolvens SDM. Both bifunctional acetaldehyde/ethanol dehydrogenase AdhE-catalyzed ethanol production and acetate-induced 2,3-BD biosynthesis are indispensable for the elimination of acetate generated during overflow metabolism. 2,3-BD biosynthesis from glucose supplies NADH required for acetate elimination via AdhE-catalyzed ethanol production. The coupling strategy involving 2,3-BD biosynthesis and ethanol production is widely distributed in bacteria and is important for toxic acetate elimination. Finally, we realized the co-production of ethanol and acetoin from chitin, the second most abundant natural biopolymer whose catabolism involves inevitable acetate production through the coupling acetate elimination strategy. The synthesis of a non-toxic chemical such as 2,3-BD may be viewed as a unique overflow metabolism with desirable metabolic functions.