Co-production Of Ethanol Research Articles

PSXI-10 Effects of feeding doses of enzyme complex and corn ethanol coproduct on performance and carcass traits of finishing beef cattle

Abstract The use of enzyme complex and the inclusion of corn ethanol co-products are strategies that can increase feed efficiency and carcass weight of feedlot beef cattle. Crossbred bulls (n = 389) were assigned to a randomized completed block design, according to their initial shrunk body weight (BW; 314 ± 40 kg; 10 pen/treatment). The treatment arrangement was a 2 × 3 factorial, with Factor 1 defined by the inclusion of corn dried bran/fiber plus distillers solubles (15 or 45% of DFS; FS Ouro from FS Bioenergy) and factor 2 defined by the increasing doses of multicarbohydrase complex (Rovabio Advance from Adisseo Company; 0, 0.75 or 1.0 g for every 10 kg of diet DM)). The diets contained 8.5% sugar cane bagasse, 44 or 73% ground flint corn, 15 or 45% DFS, 0.5 or 1.5% urea and 2% mineral mix plus monensin (30 ppm in the diet) with the respective enzyme complex doses. On d -1 and 122, individual BW were recorded after a 16-h of fasting (feed and water). The dry matter (DM) intake (DMI) was determined by the difference of feed offer and orts samples after dried at 105°C for 24 h to determine DM. The pen average daily gain (ADG) and DMI were used to calculate feed efficiency (ADG/DMI). On d 122, subcutaneous fat thickness (FT) and the rib eye area (REA) were obtained by means of an ultrasound image, and hot carcass weight (HCW) was obtained upon slaughter on the next day. Data were analyzed using the MIXED procedure of SAS. There was no interaction between the inclusion of DFS and enzyme doses for the variables evaluated (P > 0.05). The use of enzyme complex had no effect on cattle DMI, ADG and FE (P > 0.05). No effects of DFS levels were observed on daily DMI (P ≥ 0.45) or final BW (P ≥ 0.33). Nonetheless, cattle fed 45% DFS had greater ADG (1.37 vs. 1.28 kg; P = 0.02) and FE (153 vs. 145 g/ kg; P = 0.03) than cattle fed 15% DFS. There was no effect of the inclusion of DFS or the doses of the enzyme complex on the carcass parameters evaluated. In summary, including 45% DFS in finishing diets improved feedlot cattle performance compared with 15%. The use of the enzyme complex did not affect animal performance.

PH Effects in the Electrochemical Reduction of CO at Cu Electrocatalysts in an MEA Cell Configuration

We explore the impact of pH and buffer on the electrochemical reduction of CO at Cu electrocatalysts in a membrane electrode assembly (MEA) cell. Anolytes included alkaline KOH solution with potassium hydrogen phosphate and potassium dihydrogen phosphate buffers with pH values ranging from 8 to 14. Results show near-neutral pH electrolytes enhance acetate selectivity. Figure 1 shows Faradaic efficiencies to acetate over 85% at a current density of 300 mA/cm². More alkaline electrolytes resulted in increasing HER along with coproduction of ethanol and n-propanol.Previous works have shown that ethylene production is enhanced at near-neutral pH values and other works have demonstrated that acetate is more favored in alkaline conditions, with ketene identified as a key intermediate. This study highlights the role of phosphate buffers in acetate selectivity at near-neutral pH. SEM, XPS, and XRD analyses show morphological and compositional changes in the Cu catalyst under different pH conditions. We propose that the phosphate buffers stabilize acetate precursors.Figure 1: Electrochemical performance measurement at different anolyte pH; Faradaic Efficiency of H2, C2H4, CH4, Ethanol, Acetate, and n-Propanol during CO electroreduction in a zero-gap MEA configuration at 300 mA*cm−2. Figure 1

Brazilian Corn Ethanol Coproducts for Pigs: Feeding Value and Blood Parameters.

This study aimed to determine the values of net energy (NE), digestible energy (DE) and metabolizable energy (ME) and digestibility coefficients of corn ethanol coproducts produced in Brazil and their effects on the nitrogen balance and blood parameters of pigs. Ten barrows were housed in metabolic study cages for total collection and fed a reference diet (RD) or 800 g/kg RD + 200 g/kg of a coproduct of corn ethanol. Distiller's dried grains with solubles (DDGS), corn bran with solubles (CBS), distiller's dried grains (DDG) and high-protein distiller's dried grain (HPDDG) were evaluated. The experimental design was randomized blocks with three repetitions per period, totaling six repetitions per diet. Diets containing the HPDDG had greater DE and ME than those containing CBS and DDGS and greater DE than those containing the DDG (p < 0.05). HPDDG, DDG, CBS and DDGS showed 4498, 3419, 3029 and 3335 kcal/kg DE; 4366, 3305, 2934 and 3214 kcal/kg ME; and 2515, 1938, 1649 and 1725 kcal/kg NE, respectively. Pigs fed diets containing HPDDG and CBS showed greater nitrogen retention efficiency than pigs fed DDGS (p < 0.05). Pigs fed diets containing HPDDG had higher blood urea levels than pigs fed CBS and RD, while triglyceride levels in animals that received the CBS diet were greater than those in animals that received all other diets. The HPDDG had the highest energy levels and the best digestibility coefficients. The chemical composition of coproducts influences the nitrogen balance and circulating levels of urea and triglycerides in pigs.

Valorization of process wastes from soft-wheat processing industry through biofuel production.

A substantial amount of process waste is generated during the manufacture of soft-wheat products (SWPs), such as biscuits/cookies, crackers, wafers, and cakes. A small portion of waste is reused in specific biscuits, whereas the rest is usually discarded. This study aimed to investigate the suitability of this waste for the co-production of bioethanol and fatty acid methyl esters (FAMEs or biodiesel). Two groups of waste generated in the SWP industry were included in the study: (a) the waste of low-moisture (<10%) biscuits, crackers, and wafer sheets with no fillings and/or coatings, and (b) the waste of high-moisture (>10%) biscuits, crackers, wafers, and cakes with fillings and/or coatings. The study involved extracting each sample with hexane, and the recovered fat was converted to the FAME through alkali-catalyzed transesterification. The remaining carbohydrate-rich fraction was then converted to bioethanol through amylolytic hydrolysis and yeast fermentation. A great portion (92.42%-93.17%) of the fat was extracted from the wastes and converted to the FAME with adequate yields (13.81-14.55g FAME/g waste, dm) and acceptable conversion efficiencies (85.19%-89.04%). However, bioethanol production from the defatted carbohydrate-rich fractions proceeded rather slowly, yielding only 16.54-18.02 (g ethanol per g of waste, dm), corresponding to fermentation efficiencies ranging from 43.32% to 48.29%. Upon the co-production of FAME and ethanol, a considerable amount (50.93%-53.08%) of waste solids remained in the residue fraction. These findings indicated that production of the FAME with adequate yields and conversion efficiencies is viable from the SWP industry wastes; however, bioethanol yields and fermentation efficiencies are rather limited, which warrants further investigation. PRACTICAL APPLICATION: The soft-wheat processing industry generates 1%-5% of total production as waste. The waste was studied to produce FAME and bioethanol. The fat was extracted from the waste and converted to FAME. Bioethanol yields and fermentation efficiencies are limited due to dough modifiers and antimicrobial additives used in SWP production. Further research is required to improve ethanol yield.

Cell Recycling Application in Single-Stage and Sequential-Stage Co-Production of Xylitol and Ethanol Using Corn Cob Hydrolysates

A sustainable bioeconomy in agricultural and agro-industrial production must inevitably involve the sustainable use of agricultural residues through zero-waste processes. Corn cob is considered crucial agricultural waste as 278 and 293 million tons were produced worldwide in 2022 and 2023, respectively. Corn cob hydrolysates, which are abundant in xylose and glucose, could be efficiently utilized for xylitol and ethanol production through the cultivation of recycling the yeast strain Candida magnoliae TISTR 5664 in the single-stage and sequential-stage co-production of these products. The statistically significant maxima (p ≤ 0.05) ethanol concentrations were improved by 7.8% (49.9–51.7 g/L or 91.3–95.6% of the theoretical) from the single stage of ethanol production employing recycled cells and 9.9% (50.9–54.1 g/L or 77.3–83.9% of the theoretical) from the second step of sequential-stage co-production using recycled cells without xylitol accumulation. Conversely, the single-stage xylitol production utilizing recycled cells under microaerobic conditions resulted in a statistically significant lower (p ≤ 0.05) xylitol concentration by two folds relative to the control, while ethanol concentration was elevated by almost double. The statistically significant maximum (p ≤ 0.05) xylitol was achieved at 25.9 g/L (58.6% of the theoretical) when sequential-stage co-production was initiated in the first step with fresh inoculum only and not recycled cells. The sequential-stage co-production of xylitol and ethanol presented the potential for statistically significant improvement (p ≤ 0.05) of both xylitol and ethanol production processes.

Enhanced co-production of hydrogen and ethanol from brown algae fermentation by supplementing nano zero-valent iron (nZVI)

Nano zero-valent iron (nZVI) has been shown to facilitate biofuel production, notably in hydrogen generation. However, its effect on bioethanol production is rarely studied, and even less so on its impact on hydrogen and ethanol co-production. This study therefore conducted ethanol-type hydrogen-producing fermentation with brown algae to explore the effect of nZVI. With the supplementation of nZVI, fermentation was accelerated and the production of hydrogen and ethanol were both significantly enhanced. At the optimal nZVI concentration of 100 mg/L, the production of hydrogen and ethanol increased by 71.44% and 65.11%, respectively. A high hydrogen yield of 2.32 mol/mol-mannitol was achieved. The ethanol yield (1.86 mol/mol-mannitol) reached 93% of the theoretical maximal yield with a high selectivity of 91.09%. Electron distribution analysis showed that nZVI increased the total electron amounts of fermentation, and directed more electrons to ethanol than hydrogen. The reduced redox potential (ORP) and increased NADH level further confirmed the role of nZVI. Moreover, nZVI fostered Fe2+ availability to hydrogen-producing bacteria, enhancing the enzymes hydrogenase and alcohol dehydrogenase, as well as cell biomass. The bioenergy conversion efficiency (BioECE) improved from 19.08% to 31.74% with 100 mg/L nZVI treatment. This study provided a first demonstration regarding the role of nZVI in hydrogen and ethanol co-production, highlighting the great potential of multiple bioenergy recovery from marine biomass.

Comprehensive reutilization of Glycyrrhiza uralensis residue by extrusion-biological pretreatment for coproduction of flavonoids, cellulase, and ethanol

A continuous chemical-free green approach was investigated for the comprehensive reutilization of all components in herbal extraction residues (HERs), taking Glycyrrhiza uralensis residue (GUR) as an example. The GUR structural changes induced by mechanical extrusion which improve the specific surface area and enzyme accessibility of GUR. With 3 % pretreated GUR loading of high-tolerance Penicillium oxalicum G2. The reducing sugar yield of 11.45 g/L was achieved, along with an 81.06 % in situ enzymatic hydrolysis. Finally, 8.23 g/L bioethanol (0.40 g/g total sugar) was produced from GUR hydrolysates after 24 h fermentation of Pichia stipitis G32. The amount of functional medicinal ingredients extracted from GUR after hydrolysis (39.63 mg/g) was 37.69 % greater than that of un-pretreated GUR. In total, 1.49 g flavonoids, 294.36 U cellulase, and 14.13 g ethanol could be produced from 100 g GUR using this process, illustrating that this green and efficient process has the potential for industrial production.

Economic Research on Ethanol Feed-Use Coproducts: A Review, Synthesis, and Path Forward.

During the mid-2000s to the early 2010s, the domestic ethanol industry witnessed substantial growth, with ethanol coproducts emerging as vital elements for plant profitability and livestock feeding. Initially serving as supplementary revenue streams, coproducts from ethanol production have evolved into diverse value-added offerings, bolstering revenue streams, and sustaining profit margins. This study reviews existing economic research on ethanol coproducts, detailing methodologies, product focus, and research locations. Initially gathering 972 articles from 9 databases, 110 articles were synthesized. We find that most studies primarily examined the growth and future of the ethanol industry with a limited focus on specific coproducts. Feed-use distillers' grains, especially dried distillers' grains, were the most widely published while newer coproducts like pelletized, de-oiled, and high-protein distillers' grains were relatively understudied. Non-feed-use products were notably overlooked, highlighting the need for exploration beyond conventional applications. The evolving market landscape for ethanol co-products has surpassed published academic understanding of the economic tradeoffs necessitating further research into product dynamics, pricing, marketing, market structures, and regulatory frameworks. This highlights and underscores the importance of investigating value-added grains across diverse commodities and geographic contexts to inform strategic decision-making and policy formulation.

Application of recyclable iron-based supplementation for promoting biohydrogen and ethanol co-production

Supplementation additives is a promising approach in enhancing hydrogen production during fermentation processes, owing to the advantages of simple operation and low energy consumption. Exploring efficient and recyclable additives is a pivotal issue for its industrial applications. In this study, a magnetic recyclable iron-based biochar (FeBCs) was synthesized by one-step co-pyrolysis of straw biomass and K2FeO4 to enhance hydrogen production of Ethanoligenens harbinense. Results showed that the biochar derived by pyrolysis at 1000 °C (FeBC1000) established the highest H2 yield (2.09 mol·H2/mol·glucose) and ethanol yield (82.35 ± 3.27 mM) being 41.21 % and 22.27 % higher than that of the control group, respectively. The addition of FeBCs facilitated the substrate consumption and the excretion of protein and carbohydrate in extracellular polymeric substance (EPS). Magnetic FeBC1000 displayed the remarkable reusability, and the H2 yield was 33.59 % higher than that of the control group after being recycled for three times. The mechanism of FeBC1000 enhancing hydrogen production was that it promoted hydrogenase activity by reducing the redox potential, enhancing electron transfer, buffering the pH, releasing ferrous ions, and promoting cell immobilization. Overall, the study provided a recyclable and efficient magnetic additive for biohydrogen production, and operate a new direction for comprehensive utilization of straw with low energy input.

Digestibility and nutritional parameters of maize ethanol coproducts and xylanase for broiler diets

ABSTRACT 1. The objective of this study was to determine the nutritional and energy values of four maize distiller’s dried grains with solubles (DDGS) and one maize high protein distiller’s dried grains (HP-DDG) from ethanol production plants in Brazil; to evaluate the digestibility, performance, nitrogen balance and energy values for broiler chickens fed diets containing these coproducts (Experiment I); and to evaluate the effects of xylanase inclusion in diets containing maize DDGS for broilers on energy availability, digestibility, nitrogen balance and gastrointestinal morphometry (Experiment II). 2. For each experiment, 180 broiler chickens aged 17 and 30 days with initial weights of 450 ± 18 g and 1228 ± 33 g, respectively, were used; the chickens were distributed into 36 metabolism cages. The experimental design consisted of complete randomised blocks, with six replications per treatment and five birds per experimental unit. The treatments consisted of a basal diet (BD) and five test diets containing maize ethanol coproducts (Experiment I) one BD and five test diets containing DDGS with inclusions of 0, 8,000, 16,000, 24,000 and 32,000 BXU/kg xylanase (Experiment II). In Experiment I, HP-DDG and DDGS2 presented higher AME and AMEn values (14.1 and 13.9 MJ/kg and 13.4 and 13.3 MJ/kg, respectively), than did the other coproducts (p < 0.05). Compared with DDGS1 and DDGS3, DDGS4 and HP-DDG had higher digestible CP values (p < 0.05). In Experiment II, the inclusion of the enzyme quadratically affected the values of digestible CP and digestible EE (p < 0.05), with the maximum values occurring with the inclusion of 18 750 and 22,170 BXU/kg of xylanase, respectively. 3. The digestible NDF and digestible MM values linearly increased with the inclusion of xylanase (p < 0.05). The addition of xylanase had no effect on gastrointestinal morphometry (p > 0.05). It was concluded that the inclusion of between 18,000 and 22,000 BXU/kg of xylanase resulted in better digestible CP and digestible EE values.

Economic co-production of cellulosic ethanol and microalgal biomass through efficient fixation of fermentation carbon dioxide

An integrated process for the co-production of cellulosic ethanol and microalgal biomass by fixing CO2 generated from bioethanol fermentation is proposed. Specifically, over one-fifth of the fermentative carbon was converted into high-purity CO2 during ethanol production. The optimal concentration of 4 % CO2 was identified for the growth and metabolism of Chlorella sp. BWY-1. A multiple short-term intermittent CO2 supply system was established to efficiently fix and recycle the waste CO2. Using this system, economical co-production of cellulosic ethanol by Zymomonas mobilis and microalgal biomass in biogas slurry wastewater was achieved, resulting in the production of ethanol at a rate of 0.4 g/L/h and a fixed fermentation CO2 of 3.1 g/L/d. Moreover, the amounts of algal biomass and chlorophyll a increased by over 50 % and two-fold, respectively. Through techno-economic analysis, the integrated process demonstrated its cost-effectiveness for cellulosic ethanol production. This study presents an innovative approach to a low-carbon circular bioeconomy.

Novel approach for corn straw biorefineries: Production of xylooligosaccharides, lignin and ethanol by nicotinic acid hydrolysis and pentanol pretreatment

The productive separation and conversion of corn straw offers significant prospects for the economic viability of biorefineries centered on straw resources. In this work, a graded utilization method was proposed to produce xylo-oligosaccharides (XOS), ethanol and lignin from corn straw by nicotinic acid (NA) hydrolysis and water/pentanol pretreatment. A XOS yield of 52.6 % was achieved under optimized conditions of 100 mM NA, 170 °C and 30 min. The solid residue was directly treated with water/pentanol, achieving a lignin removal rate of 79.7 %, and the total XOS yield was improved to 62.6 %. The lignin recovered from pentanol had a high purity of 97.6 %, with high phenolic OH content. Simultaneous saccharification and fermentation of final residue resulted in an ethanol yield of 92.0 %, which yielded 55.3 g/L ethanol. Thus, NA hydrolysis and water/pentanol pretreatment provided an efficient, environmentally friendly approach to fractionate corn straw for the co-production of XOS, ethanol, and lignin.

Efficient hydrogenation of cyclohexyl acetate to cyclohexanol with Cu–Zr catalysts

A Cu3Zr7-SG catalyst prepared by the sol–gel method was active and selective for the hydrogenation of acetic acid–derived cyclohexyl acetate to yield cyclohexanol (an important chemical to produce ε-caprolactam) with co-production of ethanol.

Co-Production of Ethanol from Starch and Cellulose in Corn during Simultaneous Saccharification and Fermentation

First-generation (IG) ethanol production is corn starch to ethanol fermentation, and dosing cellulase at the beginning of the fermentation is termed in situ 1.5 G ethanol production. Co-production of corn starch and cellulose ethanol (1.5 G) was compared to a conventional 1G corn starch ethanol fermentation process to determine cellulosic ethanol yield. The analytical methods developed from this study for the quantitation of various modes of starch and cellulose will allow in situ 1.5 G ethanol producers to find the fraction of cellulosic ethanol eligible for D3 Renewable Identification Numbers (RINs). The fermentable starch, resistant starch (total starch minus fermentable starch), and cellulose were reduced in DDGS from 1 G to 1.5 G. Ethanol yield increased by 2% from 1G to 1.5 G. Among the 2% ethanol increase, more than half was cellulosic-based. This study developed high precision and accuracy analytical methods for quantifying various modes of starch and cellulose in corn matrix, which will allow corn ethanol manufacturers to find the fraction of ethanol eligible for the cellulosic ethanol credit.

Comprehensive Treatment Strategy for Banana Inflorescence Bract to Synthesize Biodiesel and Bioethanol Through Fungal Biorefinery

Banana inflorescence bract (BIB), an agro-waste is sporadically explored for second-generation biofuel production in spite of having considerable holocellulosic composition (cellulose-35.56%, w/w; hemicellulose-22.41%, w/w). In this study, an attempt has been made to utilize this substrate for fermentable sugars (pentose-C5 and hexose-C6) extraction which were employed for the co-production of microbial lipids and ethanol using Rhodosporidium toruloides NCIM 3547 and Saccharomyces cerevisiae respectively. Since, a considerable amount of lignin (8.78%, w/w) is present in BIB, a hybrid pretreatment and carbohydrate hydrolysis through microwave (160 W) assisted mild H2SO4 acid 2.5% (v/v) was adopted. The resultant liquor contains holocellulosic sugars (C5 and C6 sugars), out of which xylose (10.40 ± 0.49 g/L) and glucose (51.48 ± 1.14 g/L). Hence, it was used as the growth medium for R. toruloides to produce lipids i.e., single cell oil (SCO). The maximum lipid content was found to be 44.89 ± 1.25 (%, w/w) containing total saturated fatty acids of 89.07% which justifies its potential application in biodiesel production. On the other hand, the pretreated solid fraction containing cellulose was saccharified using cellulolytic enzyme produced by Aspergillus sp. with saccharification (%) of 69.99 ± 0.30 (%, v/w) and yield of 27.22 ± 0.33 g/L of reducing sugar. This enzymatic hydrolysate was used for ethanol production by Saccharomyces cerevisiae resulting in an ethanol yield of 12.70 ± 0.09 g/L and productivity of 0.132 g/L/h. Based on this outcome, a sustainable route for agro-waste management of BIB was laid by favouring the integrated production of biodiesel and bioethanol towards a biorefinery approach. Exploration and utilization of an agro-waste, banana inflorescence bract is established as a potent feedstock for the co-production of single cell oil and bioethanol is reported for the first time. Microwave-assisted mild acid pretreatment was performed for effective delignification and hydrolysis of holocellulosic components. The resultant liquid hydrolysate consisting of lignin degradatory compounds, pentose (xylose) and hexose (glucose) sugars was used as a growth medium for producing single cell oil, proving its potential application in biodiesel production. Further, the pretreated solid cellulosic fraction was saccharified using crude cellulolytic enzymes and an enzymatic hydrolysate was used for the production of bioethanol through two different fermentative strategies. This study reveals that banana inflorescence bract could act as suitable biomass towards the biorefinery approach. Its complete utilization paved the way for agro-waste management that is not in existence so far according to the authors’ knowledge

Co-production of ethanol and polyhydroxybutyrate from lignocellulosic biomass using an engineered Saccharomyces cerevisiae

The development of glucose/xylose co-fermenting Saccharomyces cerevisiae has improved bioethanol yield from lignocellulosic biomass, the most abundant and sustainable resource for net-zero production of fuels and chemicals. The co-production of value-added chemicals would further improve the economic feasibility of lignocellulosic bioethanol production. Here, we developed a glucose/xylose co-fermenting S. cerevisiae strain capable of co-producing polyhydroxybutyrate, a prominent biodegradable polymer, as an intracellularly accumulated co-product by introducing a polycistronic polyhydroxybutyrate biosynthetic pathway. The engineered strain accumulated polyhydroxybutyrate with a content of 64 mg/g DCW while maintaining extracellular production of ethanol with a high yield (0.43 g ethanol/g sugar). The co-production of ethanol and polyhydroxybutyrate was then evaluated using various types of biomass, including sugarcane bagasse, silver grass, and even cardboard boxes. This study demonstrates the feasibility of co-production of bioethanol and value-added chemicals to maximize the values derivable from lignocellulosic biomass.

Effect of NaOH-catalyzed organosolv pretreatment on the co-production of ethanol and xylose from poplar

NaOH-catalyzed organosolv pretreatment was proposed to degrade lignin, retain cellulose and hemicellulose in poplar, and the pretreated substrates was used to produce ethanol and xylose simultaneously. After the organosolv pretreatment conducted at 205 ºC for 20 min with 1.2% NaOH, the optimal ethanol concentration and xylose yield reached 30.1 g/L and 10.3 g/100 g raw material after 48 h, respectively, and the xylose yield was positively correlated with the ethanol concentration (R2 =0.934). The alteration in chemical composition and structure enhanced the ethanol concentration and xylose yield, which was revealed by Scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier transform-infrared spectrum (FT-IR), Thermogravimetric (TG), and correlation analysis. In addition, their capacity for generating ethanol and xylose during three fermentation processes was comprehensively compared. The results indicated that SSF was beneficial to improve ethanol concentration, and SHF was in favour of enhancing xylose and ethanol yields to 95.4% and 85.3% based on retained xylan after pretreatment and the fermentable glucose, respectively. The NaOH enhanced organosolv pretreatment exhibited excellent performance in converting poplar into energy and chemicals, which presented a new idea for biomass refining.

Metabolic engineering of Zymomonas mobilis for co-production of D-lactic acid and ethanol using waste feedstocks of molasses and corncob residue hydrolysate.

Lactate is the precursor for polylactide. In this study, a lactate producer of Z. mobilis was constructed by replacing ZMO0038 with LmldhA gene driven by a strong promoter PadhB, replacing ZMO1650 with native pdc gene driven by Ptet, and replacing native pdc with another copy of LmldhA driven by PadhB to divert carbon from ethanol to D-lactate. The resultant strain ZML-pdc-ldh produced 13.8 ± 0.2g/L lactate and 16.9 ± 0.3g/L ethanol using 48g/L glucose. Lactate production of ZML-pdc-ldh was further investigated after fermentation optimization in pH-controlled fermenters. ZML-pdc-ldh produced 24.2 ± 0.6g/L lactate and 12.9 ± 0.8g/L ethanol as well as 36.2 ± 1.0g/L lactate and 40.3 ± 0.3g/L ethanol, resulting in total carbon conversion rate of 98.3% ± 2.5% and 96.2% ± 0.1% with final product productivity of 1.9 ± 0.0g/L/h and 2.2 ± 0.0g/L/h in RMG5 and RMG12, respectively. Moreover, ZML-pdc-ldh produced 32.9 ± 0.1g/L D-lactate and 27.7 ± 0.2g/L ethanol as well as 42.8 ± 0.0g/L D-lactate and 53.1 ± 0.7g/L ethanol with 97.1% ± 0.0% and 99.1% ± 0.8% carbon conversion rate using 20% molasses or corncob residue hydrolysate, respectively. Our study thus demonstrated that it is effective for lactate production by fermentation condition optimization and metabolic engineering to strengthen heterologous ldh expression while reducing the native ethanol production pathway. The capability of recombinant lactate-producer of Z. mobilis for efficient waste feedstock conversion makes it a promising biorefinery platform for carbon-neutral biochemical production.

Scale-up of 2,3-butanediol production by Paenibacillus peoriae NRRL BD-62 using constant oxygen transfer rate-based strategy

Bio-based 2,3-butanediol (2,3-BDO) production is still limited to the lab scale, although its advantages over the chemical route include optically pure isomer production and lower energy demand. Few previous studies have investigated bio-based 2,3-BDO scale-up using well-defined criteria and safe microorganisms. This study aimed to produce 2,3-BDO by a newly Paenibacillus peoriae NRRL BD-62 in a pilot bioreactor with 70 L, keeping the oxygen transfer rate (OTR) constant and below 1.68 mmolO2/L/h to ensure the microaerobic conditions. A surface aeration system was adopted, and an energy dissipation of 270.5 W/m3 and an impeller tip speed of 2.04 m/s were required. A 2,3-BDO productivity and yield of 0.90 g/L/h and 0.40 g/g, comparable to unsafe or genetically engineered microbial producers, were observed in the batch assay, respectively. No acetoin accumulation and a levo-2,3-BDO optical purity of about 98 % were achieved in 26 h. A delay in pulse feeding resulted in an ethanol coproduction (1:1 ratio) in the fed-batch assay, although the global productivity and yield were similar to the batch assay. To the best of our knowledge, this is the first time that 2,3-BDO has been produced by wild-type and safe P. peoriae strain in a pilot bioreactor keeping OTR constant.

High yield co-production of isobutanol and ethanol from switchgrass: experiments, and process synthesis and analysis

Hybrid yeast strain co-produces isobutanol and ethanol at high yields. Reducing hydrolysis enzyme loading and enhancing xylose conversion greatly impact the economic potential of the biorefinery.