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A novel salt (potassium triphosphate, K 5 P 3 O 10) induced phase separation to extraction of 2,3-butanediol (BDO) from aqueous solution and its recycling were studied. This paper investigated factors influencing salt induced phase separation (SIPS) extraction efficiency, including salt type and concentration, solute content, equilibrium time and temperature, and solution pH. With BDO concentration 15% (w/w) and K 5 P 3 O 10 concentration 600 g·kg−1, this system can achieve complete phase equilibrium within 8 min, the extraction efficiency, distribution coefficient and selectivity for BDO were 99.5 ± 0.5%, 2406.1 ± 174.5, 5940.2 ± 260.9 respectively. Moreover, the process only has two steps (shaking and standing), the extraction time was about 15 min, which was much shorter than that in previous studies reported. In addition, there was no need for solvent in extraction process, after dehydration, the purity of the product is 91.0%. Reused six times, the recovery of salt and extraction efficiency of BDO almost did not change. Finally, the binodal curves and solid-liquid equilibria line of novel SIPS system were also determined at 298.15 K. As a green technology in chemical industry, this method has the advantages of high extraction efficiency and provides a potential for separation and refining of BDO for its convenience, economy, and easy to scale-up. [Display omitted] • A novel salt induced phase separation system to extraction 2,3-butanediol from aqueous solution was proposed. • The extraction efficiency of 2,3-butanediol reached up to 99.5 ± 0.5% from aqueous solution with developed method. • Reused six times, the recovery of salt and extraction efficiency of BDO almost did not change. • The ternary equilibrium phase diagram of K 5 P 3 O 10 - 2,3-butanediol - water system was investigated. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the effectiveness of the marine macro-algae Ulva pertusa as a potential source of important chemicals, including 2,3-butanediol (2,3-BDO). This study examined how pretreatment conditions like liquid-to-solid ratio, reaction temperature, and reaction time influence the hydrolysis of U. pertusa biomass through hydrothermal pretreatment followed by enzymatic hydrolysis. Consequently, 23.44 g/L (12.7 % based on biomass weight) of reducing sugar was produced under hydrothermal pretreatment conditions (liquid-to-solid ratio of 6:1, reaction temperature of 165 °C, and reaction time of 15 min), followed by enzymatic hydrolysis. During hydrothermal pretreatment, the sugar concentration peaked at 3.68 g/L within the severity factor (SF) range of 3.5–4.4. During subsequent enzymatic hydrolysis, the sugar concentration remained stable until the SF reached 4.0. However, when SF exceeded 4.0, the sugar concentration rapidly decreased. The effectiveness of U. pertusa hydrolysate was evaluated via the fermentation of 2,3-BDO. Pantoea agglomerans successfully produced 2,3-BDO with a yield of 0.299 g/g-sugar from U. pertusa hydrolysate. In summary, this study demonstrated the effectiveness of U. pertusa hydrolysate as a bioresource for producing biochemicals, including 2,3-BDO. • Effectiveness of macro-algae Ulva pertusa as a possible source for 2,3-BDO production. • 23.44 g/L sugar yielded under hydrothermal pretreatment with subsequent enzymatic hydrolysis. • Hydrothermal pretreatment was optimized at 165 °C and 15 min with 6:1 L/S ratio. • Pantoea agglomerans yielded 0.299 g 2,3-BDO/g sugar from hydrolysate of U. pertusa. [ABSTRACT FROM AUTHOR]

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Current social needs, as well as political and environmental restrictions, have led to the generation of products within a framework of sustainability, and favoring production processes based on renewable raw materials. During the process design work, the role of the dynamic properties of a process, together with some other metrics, is not always considered. However, several studies have shown that there is a certain relationship between the dynamics and controllability of the process and its sustainability. In this work, the dynamic properties of different separation schemes for the purification of 2,3-BD from biomass fermentation are evaluated. The study allowed determining the best alternatives for the eventual implementation of these schemes, as well as the role of controllability concerning other sustainability indicators. As result, it was found that schemes that include a thermal coupling in their topological design allow a general improvement of all sustainability indicators. In addition, it was observed in this case study that process intensification contributes significantly to the fulfillment of various sustainability indicators. • It was obtained the control properties of separation alternatives to purify 2,3-Butanediol, the thermally coupled alternatives resulted as the most balanced alternatives • The sustainable evaluation allows considering a thermal coupling as a fundamental step in process design of a sustainable process. • The most intensified alternative did not result as the most sustainable alternative [ABSTRACT FROM AUTHOR]

BackgroundA microbial cell factory with high yield and productivity are prerequisites for an economically feasible bio-based chemical industry. However, cell factories that show a kinetic imbalance between glycolysis and product formation pathways are not optimal. Glycolysis activity is highly robust for survival in nature, but is not optimized for chemical production.ResultsHere, we propose a novel approach to balance glycolytic activity with the product formation capacity by precisely controlling expression level of ptsG (encoded glucose transporter) through UTR engineering. For various heterologous pathways with different maximum production rates, e.g., n-butanol, butyrate, and 2,3-butanediol, glycolytic fluxes could be successfully modulated to maximize yield and productivity, while minimizing by-product formation in Escherichia coli.ConclusionsThese results support the application of this simple method to explore the maximum yield and productivity when designing optimal cell factories for value-added products in the fields of metabolic engineering and synthetic biology.

Producing bio-based chemicals such as 2,3-butanediol using biological processes can play an important role in combatting global warming and addressing fossil oil depletion. To identify sustainable processes, this study sought to incorporate environmental considerations right from fermentation optimization at laboratory scale. As the literature review revealed discrepancies in Life Cycle Assessment of fermentation processes, the study began with a comprehensive Life Cycle Inventory for 2,3-butanediol fermentation. Five impact categories showed significant normalized values (in person.year): ionizing radiation human health (3.2.10−2), human toxicity cancer effects (7.10−3), freshwater ecotoxicity (2.6.10−3), ozone depletion (2.3.10−3), and human toxicity non-cancer effects (1.8.10−3). The main contributors to these impact categories (hotspots) were identified as: energy demand, carbon source, potassium hydroxide for pH adjustment, antifoam, and nitrogen source. The energy demand for heating was found to represent up to 45 % of the ionizing radiation human health impact. The study also examined the influence on fermentation performance and on environmental impact of: 1) oxygen supply rate in batch mode, and 2) sugar feeding rate in fed-batch mode. When the fermentation and separation steps were considered together, the fermentation conditions producing the highest 2,3-butanediol concentration (74.7 g.L−1) also resulted in the lowest impacts across all environmental impact categories. • Environmental impacts were considered for 2,3-butanediol fermentation at lab-scale. • Energy demand, potassium hydroxide, antifoam, and nitrogen source are key hotspots. • Fermentation conditions maximizing productivity do not minimize all impact categories. • When fermentation and separation are assessed together, all impacts can be minimized. [ABSTRACT FROM AUTHOR]

Microbial biomass and waste materials conversion for biochemicals production has been an alternative for energy conservation and emission reduction. While toxic substances in biomass materials and high osmotic pressure formed in fermentation-based systems block the bioconversion processes of microorganisms. In the present study, strain T4 that isolated from tobacco waste could resist toxic inhibitors such as nicotine and was suitable for generation of 2, 3-butanediol (2, 3-BD) with a high concentration of glucose (up to 20%). 30.06 and 1.54 g/L of 2, 3-BD was generated respectively from 50 g/L of tobacco waste with and without 200 g/L glucose after fermentation for 48 h. Besides, the results of biochemical tests showed that it was gram-positive and able to liquefy gelatin, hydrolyze starch and produce catalases. It could utilize glucose but not lactose as carbohydrates during fermentation. The 16S rRNA sequence and systematic analysis revealed that T4 was identified to be a Bacillus amyloliquefaciens (B. amyloliquefaciens). This work presents a promising model microorganism chassis to use the biomass waste for high value-added biochemicals production. [ABSTRACT FROM AUTHOR]

ABSTRACT Gas fermentation provides a promising platform to turn low-cost and readily available single-carbon waste gases into commodity chemicals, such as 2,3-butanediol. Clostridium autoethanogenum is usually used as a robust and flexible chassis for gas fermentation. Here, we leveraged constraint-based stoichiometric modeling and kinetic ensemble modeling of the C. autoethanogenum metabolic network to provide a systematic in silico analysis of metabolic engineering interventions for 2,3-butanediol overproduction and low carbon substrate loss in dissipated CO2. Our analysis allowed us to identify and to assess comparatively the expected performances for a wide range of single, double, and triple interventions. Our analysis managed to individuate bottleneck reactions in relevant metabolic pathways when suggesting intervening strategies. Besides recapitulating intuitive and/or previously attempted genetic modifications, our analysis neatly outlined that interventions—at least partially—impinging on by-products branching from acetyl coenzyme A (acetyl-CoA) and pyruvate (acetate, ethanol, amino acids) offer valuable alternatives to the interventions focusing directly on the specific branch from pyruvate to 2,3-butanediol. IMPORTANCE Envisioning value chains inspired by environmental sustainability and circularity in economic models is essential to counteract the alterations in the global natural carbon cycle induced by humans. Recycling carbon-based waste gas streams into chemicals by devising gas fermentation bioprocesses mediated by acetogens of the genus Clostridium is one component of the solution. Carbon monoxide originates from multiple biogenic and abiogenic sources and bears a significant environmental impact. This study aims at identifying metabolic engineering interventions for increasing 2,3-butanediol production and avoiding carbon loss in CO2 dissipation via C. autoethanogenum fermenting a substrate comprising CO and H2. 2,3-Butanediol is a valuable biochemical by-product since, due to its versatility, can be transformed quite easily into chemical compounds such as butadiene, diacetyl, acetoin, and methyl ethyl ketone. These compounds are usable as building blocks to manufacture a vast range of industrially produced chemicals.

2,3-Butanediol (2,3-BD) is a high-value chemical compound with various applications in the industry. Conversion of agricultural wastes or by-products into 2,3-BD via microbial fermentation processes would be an environmentally friendly approach to reduce waste and sustain the production of biotechnologically important chemicals. Therewithal, sterilization of waste feedstock, which is usually required before fermentation to prevent any contamination, is not a cost-effective step because of energy consuming. The present study was performed to produce 2,3-BD from molasses using immobilized cells of locally isolated and nonpathogenic Bacillus licheniformis BD43 strain under non-sterile fermentation conditions. Sodium alginate was used as entrapping agent for cell immobilization. The highest production of 2,3-BD was obtained at temperature of 55 ⁰C, pH 7, molasses concentration of 100 mL/L, bead number of 150 beads/100 mL, 5 mm bead size and incubation time of 24 h. In optimized non-sterile batch fermentation of 100 mL/L molasses (48.3 g sugar), 31.6 g/L of 2,3-BD was obtained with a yield of 0.65 g/g. Non-sterile fermentation of molasses using immobilized cells of B. licheniformis in the production of 2,3-BD was investigated for the first time. The study indicates that thermophilic B. licheniformis BD43 is a suitable candidate for non-sterile and energy-saving processes to convert waste feedstock to value-added chemicals. [Display omitted] • Conversion of molasses into biovalued compound of 2,3-Butanediol. • Bacillus licheniformis BD43 is a newly isolated thermophilic strain. • Fermentation processes were conducted under non-sterile conditions. • The strain BD43 achieved to produce 2,3-Butanediol with a high yield from molasses. [ABSTRACT FROM AUTHOR]

Chirally pure (R)-1,3-butanediol ((R)-1,3-BDO) is a valuable intermediate for the production of fragrances, pheromones, insecticides and antibiotics. Biotechnological production results in superior enantiomeric excess over chemical production and is therefore the preferred production route. In this study (R)-1,3-BDO was produced in the industrially important whole cell biocatalyst Clostridium saccharoperbutylacetonicum through expression of the enantio-specific phaB gene from Cupriavidus necator. The heterologous pathway was optimised in three ways: at the transcriptional level choosing strongly expressed promoters and comparing plasmid borne with chromosomal gene expression, at the translational level by optimising the codon usage of the gene to fit the inherent codon adaptation index of C. saccharoperbutylacetonicum, and at the enzyme level by introducing point mutations which led to increased enzymatic activity. The resulting whole cell catalyst produced up to 20 mM (1.8 g/l) (R)-1,3-BDO in non-optimised batch fermentation which is a promising starting position for economical production of this chiral chemical.

1,3-Propanediol (1,3-PDO) is an important synthetic monomer for the production of polytrimethylene terephthalate (PTT). Here, we engineered Klebsiella pneumoniae by a multi-strategy to improve 1,3-PDO production and reduce by-products synthesis. First, the 2,3-butanediol (2,3-BDO) synthesis pathway was blocked by deleting the budB gene, resulting in a 74% decrease of 2,3-BDO titer. The synthesis of lactate was decreased by 79% via deleting the ldhA gene, leading to a 10% increase of 1,3-PDO titer. Further, reducing ethanol synthesis by deleting the aldA gene led to a 64% decrease of ethanol titer, and the 1,3-PDO titer and yield on glycerol increased by 12 and 10%, respectively. Strengthening the TCA cycle by overexpressing the mdh gene improved 1,3-PDO synthesis effectively. Under 5-L fed-batch fermentation conditions, compared to wild type strain, the production of 2,3-BDO, lactate and ethanol in the mutant strain decreased by 73, 65 and 50%, respectively. Finally, the production of 1,3-PDO was 73.5 g/L with a molar yield of 0.67 mol/mol glycerol, improved 16% and 20%, respectively. This work provides a combined strategy for improving 1,3-PDO production by strengthening the TCA cycle to relieve metabolic stress by deleting genes of by-products synthesis, which was also beneficial for the extraction and separation of downstream products. [ABSTRACT FROM AUTHOR]

Biotechnologically produced 2,3-butanediol (2,3-BDO) is a potential starting material for industrial bulk chemicals, such as butadiene or methyl ethyl ketone, which are currently produced from fossil feedstocks. So far, the highest 2,3-BDO concentrations have been obtained with risk class 2 microorganisms and pure glucose as substrate. However, as glucose stays in competition to food and feed industries, a lot of effort has been done in the last years finding efficient alternative substrates. Thereby xylose from hydrolysed wood hemicelluloses is a promising substrate for the production of 2,3-BDO. The risk class 1 microorganism Bacillus vallismortis strain was identified as a very promising 2,3-BDO producer. The strain is able to utilize xylose almost in the same manner as glucose. B. vallismortis is less prone to common inhibiting compounds in lignocellulosic extracts/hydrolysates. When using a concentrated hemicellulose fraction from birch wood hydrolysate, which was produced with ultrafiltration and after which the acetate concentration was reduced, a yield of 0.43 g g [ABSTRACT FROM AUTHOR]

The isobaric vapor–liquid equilibrium (VLE) data at 101.3kPa for (1,3-propanediol(PG) + 1,3-butanediol(BD)), (1,3-PG+2,3-BD) and (1,3-BD+2,3-BD) and for the ternary system of (1,3-PG+1,3-BD+2,3-BD) have been measured. The thermodynamic properties of the non-ideal vapor phase have been considered with the EOS equation. The liquid activity coefficients have been calculated with Wilson, NRTL and UNIQUAC equations, and the binary interaction parameters were regressed by these models. The vapor composition of VLE data were calculated by the optimum parameter group and generated a good consistency to experimental values. Based on all the preceding results, a two-column distillation process was designed. [ABSTRACT FROM AUTHOR]

The volatile compound 2,3-butanediol, which is produced by certain strains of root-associated bacteria, consists of three stereoisomers, namely, two enantiomers (2R,3R- and 2S,3S-butanediol) and one meso compound (2R,3S-butanediol). The ability of 2,3-butanediol to induce plant resistance against pathogenic fungi and bacteria has been investigated; however, little is known about its effects on induced resistance against viruses in plants. To investigate the effects of 2,3-butanediol on plant systemic defense against viruses, we evaluated the disease control capacity of each of its three stereoisomers in pepper. Specifically, we investigated the optimal concentration of 2,3-butanediol to use for disease control against Cucumber mosaic virus and Tobacco mosaic virus in the greenhouse and examined the effects of drench application of these compounds in the field. In the field trial, treatment with 2R,3R-butanediol and 2R,3S-butanediol significantly reduced the incidence of naturally occurring viruses compared with 2S,3S-butanediol and control treatments. In addition, 2R,3R-butanediol treatment induced the expression of plant defense marker genes in the salicylic acid, jasmonic acid, and ethylene signaling pathways to levels similar to those of the benzothiadiazole-treated positive control. This study reports the first field trial showing that specific stereoisomers of 2,3-butanediol trigger plant immunity against multiple viruses.

2,3-Butanediol (2,3-BD) is a valuable bulk chemical owing to its extensive application in chemical and pharmaceutical industry with diverse applications in drug, cosmetics and food products. In the present study, the biotransformation of acetoin to 2,3-BD by five plant species (Brassica oleracea, Brassica rapa, Daucuscarota, Pastinaca sativa, and Raphnussativus) and five microorganisms (Aspergillusfoetidus, Penicillumcitrinum, Saccharomyces carlbergensis, Pichiafermentans, and Rhodotrulaglutinis) was investigated as a method for the production of 2,3-BD, which can serve as an alternative to the common pentoses and hexoses fermentation by microorganisms. The produced 2,3-BD stereoisomers were characterized and their total conversion yields were determined. The results showed that the examined plants can be used as a green factory for the production of all 2,3-BD stereoisomers, except B. rapa. In microorganisms, P. fermentans and S. carlbergensis produced (-)-2R,3R and mesobutanediol, while P. citrinum produced (+)-2S,3S and mesobutanediol. R. glutinis and A. foetidus produced all three isomers. In conclusion, efficient whole-cell biocatalysts from plants and microorganisms were determined in the bioconversion of acetoin to 2,3-BD. The profile of produced stereoisomers demonstrated that microorganisms produce more specific stereoisomers.

Plants live in close association with large communities of microbes, some of which are foliar pathogens that invade tissues, primarily via stomata on the leaf surface. Stomata are considered part of an integral, innate immunity system capable of efficiently preventing pathogens from entering the host plant. Although Bacillus, a typical plant growth-promoting rhizobacterium, is known to induce stomatal closure, the substances participating in this closure and the mechanism involved in its regulation remain poorly understood. Here, we screened a mutant library and conducted site-specific mutagenesis experiments in order to identify such substances. We found that acetoin and 2,3-butanediol from B. amyloliquefaciens FZB42 induced stomatal closure in Arabidopsis thaliana and Nicotiana benthamiana. These two components could function either via root absorption or volatilization to restrict stomatal apertures, but root absorption was more efficient. Both substances invoked the salicylic acid and abscisic acid signaling pathways to close the stomata and stimulated accumulation of hydrogen peroxide and nitric oxide. The results present comprehensive evidence of how soil rhizobacteria may affect plant stomata, in a way that reinforces the evolved mutualism between the two groups of organisms, and provide potential alternative avenues of research towards reducing the incidence of disease in crops. [ABSTRACT FROM AUTHOR]

Brown patch, caused by Rhizoctonia solani , is a serious disease in Agrostis stolonifera . 2, 3-butanediol (2, 3-BD) is the major component of volatile organic compounds and was found to initiate induced systemic resistance (ISR). To investigate the induced resistance mechanism of 2, 3-BD, we examined the effects of resistance by area affected, along with changes in the content of phytohormones (Zeatin (ZT), Abscisic Acid (ABA) and Indole-3-Acetic Acid (IAA)), the activities of three phenylpropanoid metabolic enzymes (Phenylalaninammo-Nialyase (PAL), Chalcone Isomerase (CHI) and 4-Coumarate:Coenzyme A Ligase (4CL)) and the level of secondary metabolites (total phenols, flavonoid and lignin). The result showed that 2, 3-BD treatment at 250 μmoL/L had the best induction effect with the area affected decreased from 95% of the control to 55%. Compared to the controls, treatment with 250 μmoL/L 2, 3-BD induced higher levels of PAL, CHI and 4CL activity and increased total phenols, flavonoid and lignin levels. While 2, 3-BD treatment decreased the content of ZT and ABA but increased the content of IAA compared to controls. This study provides a basis for elucidating the mechanism of 2, 3-BD as a new plant disease control agent. [ABSTRACT FROM AUTHOR]

Sodium percarbonate (SP), a kind of alkaline strong oxidant, was applied to corncob pretreatment. The optimized pretreatment conditions were at 4% (w/v) SP concentration with solid-to-liquid (SLR) ratio of 1:10 treating for 4 hr at 60°C. This pretreatment resulted in 91.06% of cellulose and 84.08% of hemicellulose recoveries with 34.09% of lignin removal in corncob. The reducing sugar yield from SP-pretreated corncob was 0.56 g/g after 72 hr of enzymatic hydrolysis, 1.75-folds higher than that from raw corncob. 2,3-butanediol production by Enterobacer cloacae in simultaneous saccharification fermentation was 29.18 g/L using SP-pretreated corncob as a substrate, which was 11.12 times of that using raw corncob. Scanning electron microscope, X-ray diffraction, and Fourier transform infrared spectra analysis indicated that physical characteristics, crystallinity, and structure of corncob had changed obviously after SP pretreatment. This simple and novel pretreatment method was effective for delignification and carbohydrate retention in microbial production of 2,3-butanediol from lignocellulose biomass. [ABSTRACT FROM AUTHOR]

The bacterial strain Enterobacter ludwigii FMCC 204 was selected as the most efficient 2,3-butanediol (BDO) producer among five strains when cultivated on glucose, fructose, mannose, arabinose, xylose, galactose and sucrose in shake flask cultures. Plums, apples and pears were used for the production of fermentation medium via sequential maceration, suspension in water and centrifugation to collect the supernatant. Sugar production from mixed vegetables was evaluated via sulphuric acid treatment leading to 65.8% (w/w) of hemicellulose hydrolysis yield at initial solid concentrations of 50 g/L (on a dry basis) treated with 3% (v/v) H2S04. Fed-batch cultures of E. ludwidgii on fruit derived feedstock resulted in BDO concentration, yield and productivity of 50 g/L, 0.4 g/g and 0.41g/I/h. BDO production from vegetable waste hydrolysates via fed-batch cultures led to BDO concentration of 17.6 g/L. This study demonstrated th a t fruit and vegetable wastes from open markets can be used as fermentation feedstocks for BDO production. [ABSTRACT FROM AUTHOR]

The volatile compound 2,3-butanediol, which is produced by certain strains of rootassociated bacteria, consists of three stereoisomers, namely, two enantiomers (2R,3Rand 2S,3S-butanediol) and one meso compound (2R,3S-butanediol). The ability of 2,3-butanediol to induce plant resistance against pathogenic fungi and bacteria has been investigated; however, little is known about its effects on induced resistance against viruses in plants. To investigate the effects of 2,3-butanediol on plant systemic defense against viruses, we evaluated the disease control capacity of each of its three stereoisomers in pepper. Specifically, we investigated the optimal concentration of 2,3- butanediol to use for disease control against Cucumber mosaic virus and Tobacco mosaic virus in the greenhouse and examined the effects of drench application of these compounds in the field. In the field trial, treatment with 2R,3R-butanediol and 2R,3Sbutanediol significantly reduced the incidence of naturally occurring viruses compared with 2S,3S-butanediol and control treatments. In addition, 2R,3R-butanediol treatment induced the expression of plant defense marker genes in the salicylic acid, jasmonic acid, and ethylene signaling pathways to levels similar to those of the benzothiadiazoletreated positive control. This study reports the first field trial showing that specific stereoisomers of 2,3-butanediol trigger plant immunity against multiple viruses. [ABSTRACT FROM AUTHOR]

A safe microorganism (class 1), Paenibacillus polymyxa, was used for 2,3-butanediol and acetoin production, which could make the fermentation process cheaper and less complex. It showed a broad substrate spectrum, such as mannose, galactose, cellobiose, glycerol, the mixture of glucose and xylose, and the mixture of glucose and cellobiose. In addition, the strain can utilize highly concentrated glucose that was obtained by enzymatic hydrolysis of ionic liquid-pretreated cellulose. With a 15% initial cellulose consistency, the final glucose concentration was 109.5 g/L with 65.7% glucose yield. Without any treatment, the hydrolysate was successfully used to produce 2,3-butanediol and acetoin with a yield of 81.7% and a productivity of 0.7 g/(L•h) by Paenibacillus polymyxa. Higher concentration and higher productivity with relatively high yield, compared with previous works by acid hydrolysis, of 2,3-butanediol and acetoin were achieved. All these novel improvements offer significant opportunities to further decrease the cost of large-scale 2,3-butanediol and acetoin production.

BACKGROUND Acetoin is an important biorefinery platform chemical with many industrial uses. It is mainly produced by chemical synthesis or mesophilic fermentation with high costs. RESULTS A thermophilic Bacillus strain was isolated to efficiently produce acetoin from maize hydrolysate at 50°C. The fermentation medium was statistically optimized by Plackett-Burman design. Operational conditions were then optimized using a 4.2 L fermenter conducted at 50°C without sterilization. Oxygen enriched air (65% oxygen) accelerated substrate consumption but did not increase product titer. In comparison with 600 rpm, agitation speed controlled at 400 rpm yielded less acetoin but more 2,3-butanediol in the final products. A two-stage pH control strategy (pH first at 6.6-7.1 then at 7.7-8.0) was applied to further increase the yield of acetoin. Finally, 50.8 g L-1 of acetoin and 32.1 g L-1 of 2,3-butanediol were obtained from 251 g L-1 of degermed maize flour (dry weight). The conversion yield from sugar to the 4-carbon compounds (acetoin and 2,3-butanediol) was 94.4% of the theoretical value. CONCLUSION This is the first report of non-sterilized fermentative production of acetoin. Using degermed maize hydrolysate as the main feedstock, this work sets a new titer record of acetoin fermentation among known thermophilic producing systems. © 2017 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

This study presents the design and assessment of site-specific supply chains and related manufacturing processes for the production of bio-based chemicals from the syngas platform and via gasification of lignocellulosic biomass followed by syngas fermentation. The supply chains include feedstocks production and collection, biomass gasification, syngas fermentation, and downstream processing. For each of these stages, different alternatives were considered: four feedstocks (pine, corn stover, sugarcane bagasse, and eucalyptus), three products (ethanol, 2,3-butanediol and hexanoic acid), and three geographical locations (the Netherlands, the USA, and Brazil). Conceptual development and analysis of the supply chains were done through the combination of different design and assessment tools, namely biomass supply chains design, fermentation process design (based on thermodynamics and transport), process simulation, and economic and environmental assessments. The minimum selling price (MSP) and two environmental impact categories, i.e., global warming potential (GWP) and non-renewable energy use (NREU), were used as performance indicators. These were compared to data reported in scientific literature and commercial sources for similar processes and ­products. The best overall performance was obtained for the production of 2,3-butanediol from pine sourced in the USA. In the cases of ethanol and hexanoic acid, the syngas fermentation stage had significant contributions to MSP, GWP, and NREU, due mainly to its high energy requirements. Regarding the geographical location, the best economic performance was obtained for the USA followed by the Netherlands and Brazil respectively. Furthermore, operation in Brazil led to the lowest environmental impacts, followed by the Netherlands and the USA. © 2017 Society of Chemical Industry and John Wiley & Sons, Ltd [ABSTRACT FROM AUTHOR]

BACKGROUND 2,3-Butanediol (2,3- BD) has a wide range of applications in chiral molecular synthesis, biofuel additives, and in food flavor additive manufacturing. Fermentation is a favorable method for 2,3- BD production. However, it requires much time and produces several NADH related byproducts which compete with 2,3- BD production. Bacillus subtilis has an excellent ability for 2,3- BD production by biocatalysis. However, its production is limited by low intracellular NADH and the reversible property of acetoin reductase ( AR/2,3- BDH). The whole cell biocatalyst process with two different NADH regeneration systems was designed for efficient production of 2,3- BD in B. subtilis 168. RESULTS Formate dehydrogenase and glucose dehydrogenase for NADH regeneration were successfully co-expressed with acetoin reductase in B. subtilis 168. After optimization of biocatalyst bioconversion conditions, B. subtilis 168/ pMA5- bdhA-HpaII- fdh yielded 74.5 g L−1 of 2, 3-BD with 9.3 g L−1 h−1 productivity by fed batch and 115.4 g of 2,3-BD was achieved using same batch bacterium by three repeated batch bioconversions. On the other hand, 63.7 g L−1 of 2, 3-BD was produced with 7.92 g L−1 h−1 productivity by B. subtilis 168/pMA5- bdhA-HpaII- gdh. To our knowledge, the volume productivity obtained here is the highest ever reported for biocatalysis. CONCLUSION A higher productivity of 2,3-BD from acetoin was achieved by whole cell biocatalysis with NADH regeneration systems in B. subtilis 168. This approach can be applied for NADH related bio-based chemicals production to improve titer, yield and productivity. © 2017 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Sweet sorghum juice (SSJ) is considered a good carbon source for biorefinery due to its low price and high fermentable-sugar content. In this study, 2,3-butanediol (2,3-BD) production from SSJ by Serratia marcescens H30 was investigated. First, the medium compositions including the contents of SSJ, nitrogen source, and mineral salts were optimized in conical flasks using a single factor and orthogonal design method. Under the optimal conditions, the 2,3-BD concentration reached up to 33.40 g/L. Then the optimized medium was used to perform fermentative experiments in a 5-L bioreactor. In batch experiments, the effects of various agitation speeds on 2,3-BD production were compared. Based on batch process results, an efficient two-stage fermentative control strategy was developed, where the agitation speed was maintained at 300 rpm in the first 12 h and subsequently switched to 200 rpm. About 43.32 g/L 2,3-BD was obtained by using this strategy. Finally, fed-batch fermentation was conducted through feeding the concentrated SSJ and a maximum 2,3-BD concentration of 109.44 g/L with the productivity of 1.40 g/L·h; a yield of 83.02% was achieved. The results showed that SSJ could be used as an economical substrate for efficient 2,3-BD production by S. marcescens H30. [ABSTRACT FROM AUTHOR]

BACKGROUND The fluid dynamic conditions play a key role in the development and scaling-up of bioprocesses. In aerobic cultures, oxygen is an essential substrate for microbial growth, production and culture maintenance; an effective gas-liquid transfer must be achieved. Changes in fluid dynamics due to stirrer speed can affect the culture negatively, causing hydrodynamic stress (increasing shear stress) or oxidative stress (by an increase of available oxygen in the liquid phase). RESULTS Under oxygen-limiting conditions, specific growth rate increases with stirrer speed, and several fermentation products were specifically released to the culture medium. 2,3-butanediol production increased with stirrer speed, reaching a maximum at 400 rpm. When the agitation was increased over 550 rpm, the metabolic flux was mainly routed to increase the cell growth. Negative effects of fluid dynamic conditions on biomass production were observed at 1900 and 2000 rpm. Cellular response to shear stress conditions was also shown in the large increase of the broth viscosity over time. CONCLUSIONS Raoultella terrigena is able to adapt the carbon metabolic flux to the availability of oxygen, producing fermentation products, alcohols or directing microbial growth. Moreover, cells can withstand aggressive agitation conditions (up to 1600 rpm). © 2016 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The nonnatural alcohol 1,3-butanediol (1,3-BDO) is a valuable building block for the synthesis of various polymers. One of the potential pathways for the biosynthesis of 1,3-BDO includes the biotransformation of acetaldehyde to 1,3-BDO via 3-hydroxybutanal (3-HB) using aldolases and aldo-keto reductases (AKRs). This pathway requires an AKR selective for 3-HB, but inactive toward acetaldehyde, so it can be used for one-pot synthesis. In this work, we screened more than 20 purified uncharacterized AKRs for 3-HB reduction and identified 10 enzymes with significant activity and nine proteins with detectable activity. PA1127 from Pseudomonas aeruginosa showed the highest activity and was selected for comparative studies with STM2406 from Salmonella enterica serovar Typhimurium, for which we have determined the crystal structure. Both AKRs used NADPH as a cofactor, reduced a broad range of aldehydes, and showed low activities toward acetaldehyde. The crystal structures of STM2406 in complex with cacodylate or NADPH revealed the active site with bound molecules of a substrate mimic or cofactor. Site-directed mutagenesis of STM2406 and PA1127 identified the key residues important for the activity against 3-HB and aromatic aldehydes, which include the residues of the substrate-binding pocket and C-terminal loop. Our results revealed that the replacement of the STM2406 Asn65 by Met enhanced the activity and the affinity of this protein toward 3-HB, resulting in a 7-fold increase in kcat/Km. Our work provides further insights into the molecular mechanisms of the substrate selectivity of AKRs and for the rational design of these enzymes toward new substrates. IMPORTANCE In this study, we identified several aldo-keto reductases with significant activity in reducing 3-hydroxybutanal to 1,3-butanediol (1,3-BDO), an important commodity chemical. Biochemical and structural studies of these enzymes revealed the key catalytic and substrate-binding residues, including the two structural determinants necessary for high activity in the biosynthesis of 1,3-BDO. This work expands our understanding of the molecular mechanisms of the substrate selectivity of aldo-keto reductases and demonstrates the potential for protein engineering of these enzymes for applications in the biocatalytic production of 1,3-BDO and other valuable chemicals. [ABSTRACT FROM AUTHOR]

ABSTRACT The nar promoter, a dissolved oxygen (DO)-dependent promoter in Escherichia coli, is simply induced and functional in any cell growth phase, which are advantageous for producing biochemicals/fuels on an industrial scale. To demonstrate the feasibility of using the nar promoter in the metabolic engineering of biochemicals/biofuels in E. coli, three target pathways were examined: the d-lactate, 2,3-butandiol (2,3-BDO), and 1,3-propanediol (1,3-PDO) pathways consisting of one, three, and six genes, respectively. Each pathway gene was expressed under the control of the nar promoter. When the ldhD gene was expressed in fed-batch culture, the titer, yield, and productivity of d-lactate were 113.12 ± 2.37 g/L, 0.91 ± 0.07 g/g-glucose, and 4.19 ± 0.09 g/L/h, respectively. When three 2,3-BDO pathway genes ( ilvBN, aldB, bdh1) were expressed in fed-batch culture, the titer, yield, and productivity of ( R, R)-2,3-BDO were 48.0 ± 8.48 g/L, 0.43 ± 0.07 g/g glucose, and 0.76 ± 0.13 g/L/h, respectively. When six 1,3-PDO pathway genes ( dhaB1B2B3, yqhD, gdrA, and gdrB) were expressed in fed-batch culture, the titer, yield, and productivity of 1,3-PDO were 15.8 ± 0.62 g/L, 0.35 ± 0.01 g/g-glycerol, and 0.25 ± 0.01 g/L/h, respectively. Based on the reasonable performance comparable to that observed in previous studies using different promoters in metabolic engineering, the nar promoter can serve as a controlled expression tool for developing a microbial system to efficiently produce biochemicals and biofuels. Biotechnol. Bioeng. 2017;114: 468-473. © 2016 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Fermentation conditions for 2,3-butanediol (2,3-BD) production by Klebsiella pneumoniae CGMCC1.9131 were optimized statistically in shake flasks. Four significant factors including the initial concentrations of yeast extract, glucose, K2HPO4, and (NH4)2SO4 were optimized by Response Surface Methodology (RSM). To further improve the yield of 2,3-BD, EDTA Na2 was added to the medium. After optimization, the yield of 2,3-BD was 0.44 g/g glucose and the final concentration was 26.20 g/L when initial glucose concentration was 60 g/L. The enzymatic hydrolyzate of pretreated sugarcane bagasse by alkali-peracetic acid (PAA) and dilute acid were further used as feedstock to produce 2,3-BD under the optimized conditions, and the yields of 2,3-BD were 0.36 and 0.43 g/g consumed sugars, respectively. The experimental results indicated that the enzymatic hydrolyzate could be well converted to 2,3-BD.

Recovery of metabolites from fermentation broth by solvent extraction can be used to optimize fermentation processes. End-product reutilization, low product concentration, large volumes of fermentation broth and the requirements for large bioreactors, in addition to the high cost largely contributed to the decline in fermentative 2, 3-butanediol production. Extraction can successfully be used for in-situ alcohol recovery in 2, 3-butanediol fermentations to increase the substrate conversion.In the present work organic extraction of 2, 3-butanediol produced by Klebsiella pneumoniae fermentation was studied to detect solvent effect on 2, 3-butanediol production and determination of efficient volume of solvent. The aim of this research was liquid-liquid extractive fermentation systems evaluation as an alternative to overcome the end product effect and to increase of 2, 3-butanediol production by K. pneumoniae because conventional fermentative production of 2, 3-butanediol by K. pneumoniae hasthe disadvantage of product reutilization by the organism. The highest 2, 3-butanediol production (23.01 g/L) achieved when 20% oleyl alcohol was used.

BACKGROUND Microbial production of 2,3-butanediol (2,3- BD) with different substrates and organisms results in various 2,3- BD concentration in fermentation broths. The salting-out of 2,3- BD from different aqueous solutions with different solute content by four high-solubility salts ( K4P2O7• 3H2O, K2HPO4• 3H2O, K2CO3, K3PO4• 3H2O) were investigated at 298.15 K. RESULTS The distribution coefficient and selectivity coefficient of 2,3- BD were greatly affected by the salt composition and the initial salt concentration, but influenced by the solute content slightly. When the initial K4P2O7 concentration was higher than or equal to 550 g kg−1, 100% of 2,3- BD from the aqueous solutions was recovered, and more than 97.5% of water was removed. CONCLUSION The salting-out effects of four salts on the aqueous 2,3- BD solutions were determined in the following order: K4P2O7 > K3PO4 > K2HPO4 > K2CO3. Moreover, the solubility of 2,3- BD in both phases can be predicted in terms of the initial salt concentration and the solute content. © 2016 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Background: 2,3-Butanediol (2,3-BD) is a promising compound for various applications in chemical, cosmetic, and agricultural industries. Pyruvate decarboxylase (Pdc)-deficient Saccharomyces cerevisiae is an attractive host strain for producing 2,3-BD because a large amount of pyruvate could be shunted to 2,3-BD production instead of ethanol synthesis. However, 2,3-BD yield, productivity, and titer by engineered yeast were inferior to native bacterial producers because of the following metabolic limitations. First, the Pdc-deficient yeast showed growth defect due to a shortage of C2-compounds. Second, redox imbalance during the 2,3-BD production led to glycerol formation that lowered the yield. Results: To overcome these problems, the expression levels of Pdc from a Crabtree-negative yeast were optimized in S. cerevisiae. Specifically, Candida tropicalis PDC1 (CtPDC1) was used to minimize the production of ethanol but maximize cell growth and 2,3-BD productivity. As a result, productivity of the BD5_G1CtPDC1 strain expressing an optimal level of Pdc was 2.3 folds higher than that of the control strain in flask cultivation. Through a fed-batch fermentation, 121.8 g/L 2,3-BD was produced in 80 h. NADH oxidase from Lactococcus lactis (noxE) was additionally expressed in the engineered yeast with an optimal activity of Pdc. The fed-batch fermentation with the optimized 2-stage aeration control led to production of 154.3 g/L 2,3-BD in 78 h. The overall yield of 2,3-BD was 0.404 g 2,3-BD/g glucose which corresponds to 80.7% of theoretical yield. Conclusions: A massive metabolic shift in the engineered S. cerevisiae (BD5_G1CtPDC1_nox) expressing NADH oxidase was observed, suggesting that redox imbalance was a major bottleneck for efficient production of 2,3-BD by engineered yeast. Maximum 2,3-BD titer in this study was close to the highest among the reported microbial production studies. The results demonstrate that resolving both C2-compound limitation and redox imbalance is critical to increase 2,3-BD production in the Pdc-deficient S. cerevisiae. Our strategy to express fine-tuned PDC and noxE could be applicable not only to 2,3-BD production, but also other chemical production systems using Pdc-deficient S. cerevisiae. [ABSTRACT FROM AUTHOR]

We report the direct production of 1,3-butadiene from the dehydration of 2,3-butandiol by using alumina as catalyst. Under optimized kinetic reaction conditions, the production of methyl ethyl ketone and isobutyraldehyde, formed via the pinacol-pinacolone rearrangement, was markedly reduced and almost 80 % selectivity to 1,3-butadiene and 1,3-butadiene could be achieved. The presence of water plays a critical role in the inhibition of oligomerization. The amphoteric nature of γ-Al2O3 was identified as important and this contributed to the improved catalytic selectivity when compared with other acidic catalysts. [ABSTRACT FROM AUTHOR]

During the process of industrial production of biofuels and biochemicals from lignocellulosic biomass, large amounts of waste byproducts rich in xylose are generated, resulting in excessive wastage of natural resources and environmental pollution. In this work, xylose solution from corncob hydrolysate was utilized to produce 2,3-butanediol (2,3-BD), using the strain Enterobacter cloacae CICC 10011 to improve the utilization rate of hemicellulose and reduce environmental pollution. 2,3-BD fermentation conditions were subsequently developed. Xylose solution and (NH4)2HPO4, selected with the Plackett-Burman experiment, were determined as significant independent variables to conduct a response surface experiment. With the optimized medium, 50.02 g/L 2,3-BD production was obtained, which corresponded to 85.16% of the theoretical value. Furthermore, 81.4 g/L 2,3-BD production, 92.95 g/L the total production (2,3-BD + acetoin), and 0.72 g/(L h) productivity were obtained by fed-batch fermentation. Therefore, efficient production of 2,3-BD from corncob-derived xylose is important in the future development and expansion of biorefining technologies. [ABSTRACT FROM AUTHOR]

2,3-Butanediol (2,3-BD) is a renewable alcohol that can be prepared in high yield from biomass sugars. 2,3-BD was selectively dehydrated in a solvent-free process to a complex mixture of 2-ethyl-2,4,5-trimethyl-1,3-dioxolanes and 4,5-dimethyl-2isopropyl dioxolanes with the heterogeneous acid catalyst Amberlyst-15. The purified dioxolane mixture exhibited an anti-knock index of 90.5, comparable to high octane gasoline, and a volumetric net heat of combustion 34 % higher than ethanol. The solubility of the dioxolane mixture in water was only 0.8 g per 100 mL, nearly an order of magnitude lower than the common gasoline oxygenate methyl tert-butyl ether. The dioxolane mixture has potential applications as a sustainable gasoline blending component, diesel oxygenate, and industrial solvent. [ABSTRACT FROM AUTHOR]

Background: 2,3-Butanediol (2,3-BD) can be used as a liquid fuel additive to replace petroleum oil, and as an important platform chemical in the pharmaceutical and plastic industries. Microbial production of 2,3-BD by Bacillus licheniformis presents potential advantages due to its GRAS status, but previous attempts to use this microorganism as a chassis strain resulted in the production of a mix of D-2,3-BD and meso-2,3-BD isomers. Results: The aim of this work was to develop an engineered strain of B. licheniformis suited to produce the high titers of the pure meso-2,3-BD isomer. Glycerol dehydrogenase (Gdh) was identified as the catalyst for D-2,3-BD biosynthesis from its precursor acetoin in B. licheniformis. The gdh gene was, therefore, deleted from the wild-type strain WX-02 to inhibit the flux of acetoin to D-2,3-BD biosynthesis. The acoR gene involved in acetoin degradation through AoDH ES was also deleted to provide adequate flux from acetoin towards meso-2,3-BD. By re-directing the carbon flux distribution, the double-deletion mutant WX-02ΔgdhΔacoR produced 28.2 g/L of meso-2,3-BD isomer with >99 % purity. The titer was 50 % higher than that of the wide type. A bench-scale fermentation by the double-deletion mutant was developed to further improve meso-2,3-BD production. In a fed-batch fermentation, meso-2,3-BD titer reached 98.0 g/L with a purity of >99.0 % and a productivity of 0.94 g/L--h. Conclusions: This work demonstrates the potential of producing meso-2,3-BD with high titer and purity through metabolic engineering of B. licheniformis. [ABSTRACT FROM AUTHOR]

Background: Currently, microbial fermentation method has become the research hotspot for acetoin production. In our previous work, an acetoin-producing strain, Bacillus subtilis SF4-3, was isolated from Japanese traditional fermented food natto. However, its conversion of glucose to acetoin was relatively low. In order to achieve a high-efficient accumulation of acetoin in B. subtilis SF4-3, main medium components and fermentation conditions were evaluated in this work. Results: The by-products analysis showed that there existed reversible transformation between acetoin and 2,3-butanediol that was strictly responsible for acetoin production in B. subtilis SF4-3. The carbon sources, nitrogen sources and agitation speed were determined to play crucial role in the acetoin production. The optimal media (glucosH2O 150 g/L, yeast extract 10 g/L, corn steep dry 5 g/L, urea 2 g/L, K2HPO4 0.5 g/L, MgSO4 0.5 g/L) were obtained. Furthermore, the low agitation speed of 300 r/min was found to be beneficial to the reversible transformation of 2,3-butanediol for acetoin production in B. subtilis SF4-3. Eventually, 48.9 g/L of acetoin and 5.5 g/L of 2,3-butanediol were obtained in a 5-L fermenter, and the specific production of acetoin was 39.12% (g/g), which accounted for 79.90% of the theoretical conversion. Conclusions: The results indicated acetoin production of B. subtilis SF4-3 was closely related to the medium components and dissolved oxygen concentrations. It also provided a method for acetoin production via the reversible transformation of acetoin and 2,3-butanediol. [ABSTRACT FROM AUTHOR]

Background: 2,3-Butanediol (2,3-BDO) is a promising bio-based chemical because of its wide industrial applications. Previous studies on microbial production of 2,3-BDO has focused on sugar fermentation. Alternatively, biodieselderived crude glycerol can be used as a cheap resource for 2,3-BDO production; however, a considerable formation of 1,3-propanediol (1,3-PDO) and low concentration, productivity, and yield of 2,3-BDO from glycerol fermentation are limitations. Results: Here, we report a high production of 2,3-BDO from crude glycerol using the engineered Klebsiella oxytoca M3 in which pduC (encoding glycerol dehydratase large subunit) and ldhA (encoding lactate dehydrogenase) were deleted to reduce the formation of 1,3-PDO and lactic acid. In fed-batch fermentation with the parent strain K. oxytoca M1, crude glycerol was more effective than pure glycerol as a carbon source in 2,3-BDO production (59.4 vs. 73.8 g/L) and by-product reduction (1,3-PDO, 8.9 vs. 3.7 g/L; lactic acid, 18.6 vs. 9.8 g/L). When the double mutant was used in fed-batch fermentation with pure glycerol, cell growth and glycerol consumption were significantly enhanced and 2,3-BDO production was 1.9-fold higher than that of the parent strain (59.4 vs. 115.0 g/L) with 6.9 g/L of 1,3-PDO and a small amount of lactic acid (0.7 g/L). Notably, when crude glycerol was supplied, the double mutant showed 1,3-PDOfree 2,3-BDO production with high concentration (131.5 g/L), productivity (0.84 g/L/h), and yield (0.44 g/g crude glycerol). This result is the highest 2,3-BDO production from glycerol fermentation to date. Conclusions: 2,3-BDO production from glycerol was dramatically enhanced by disruption of the pduC and ldhA genes in K. oxytoca M1 and 1,3-PDO-free 2,3-BDO production was achieved by using the double mutant and crude glycerol. 2,3-BDO production obtained in this study is comparable to 2,3-BDO production from sugar fermentation, demonstrating the feasibility of economic industrial 2,3-BDO production using crude glycerol. [ABSTRACT FROM AUTHOR]

A new fermentation process using a mixed sugar medium is proposed in this study for 2,3- butanediol (2,3-BDO) production. The medium contained seven different monosugars known to be present in Nannochloropsis oceanica hydrolysate. The performance of each sugar when existing alone or together with glucose was evaluated. All the sugars except fucose were successfully metabolized for 2,3-BDO production. A 2,3-BDO yield of 0.31g/g was achieved with the mixed sugar medium, which was very close to that with the glucose-only medium. However, the 2,3-BDO productivity (0.28 g L-1 h-1) was found to be about 30% lower than that with glucose, implying, as expected, the existence of glucose repression on the uptake of other sugars. Strain development is in need to remove such negative effect of glucose for improved process efficiency. Fucose with the lowest uptake rate and no contribution to 2,3-BDO production can be a high value-added byproduct, once recovered and purified. [ABSTRACT FROM AUTHOR]

BACKGROUND Solvent extraction of 2,3-butanediol from dilute fermented systems is a challenging downstream unit operation. Addition of certain kosmotropic salts to the aqueous fermentation broth during the solvent extraction process can have considerable influence on the distribution of 2,3-butanediol. This work evaluates the usefulness of solvent extraction and the salting-out effect on the extraction characteristic of 2,3-butanediol in aqueous synthetic and fermented solutions. RESULTS Addition of 10 wt% dipotassium phosphate (K2HPO4) to the fermented 2,3-butanediol broth during solvent extraction results in 1.5-3-fold increase in distribution coefficient (Kd) and 7-14-fold increase in separation factor (α) for 2,3-butanediol using 2-sec butyl phenol and 1-butanol as extractants. Of various solvent-salt combinations studied; 2-sec butyl phenol + 10 wt% K2HPO4 provided Kd and α of 3.04 and 59.17 whereas 1-butanol + 10 wt% K2HPO4 provided Kd and α of 2.41 and 15.68, respectively, in fermented 2,3-butanediol broth solution. CONCLUSION This study demonstrated the prospects of repulsive salts addition to the fermented broth during the solvent extraction process. The results showed that this study may be used as a model to choose an appropriate combination of water-immiscible (hydrophobic) organic solvent and inorganic salt type and concentration for the economical recovery of 2,3-butanediol from fermentation broth. © 2014 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

ABSTRACT Enantiomerically pure (R, R)-2,3-butanediol has unique applications due to its special chiral group and spatial configuration. Currently, its chemical production route has many limitations. In addition, no native microorganisms can accumulate (R, R)-2,3-butanediol with an enantio-purity over 99%. Herein, we constructed a synthetic metabolic pathway for enantiomerically pure (R, R)-2,3-butanediol biosynthesis in Escherichia coli. The fermentation results suggested that introduction of the synthetic metabolic pathway redistributed the carbon fluxes to the neutral (R, R)-2,3-butanediol, and thus protected the strain against the acetic acid inhibition. Additionally, it showed that the traditionally used isopropyl beta-D-thiogalactoside (IPTG) induction displayed negative effect on (R, R)-2,3-butanediol biosynthesis in the recombinant E. coli, which was probably due to the protein burden. With no IPTG addition, the (R, R)-2,3-butanediol concentration reached 115 g/L by fed-batch culturing of the recombinant E. coli, with an enantio-purity over 99%, which is suitable for the pilot-scale production. Biotechnol. Bioeng. 2015;112: 1056-1059. © 2014 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]