2,3-Butanediol (2,3-BD) is a major metabolite produced by Klebsiella pneumoniae KCTC2242, which is a important chemical with wide applications. Three genes important for 2,3-BD biosynthesis acetolactate decarboxylase (budA), acetolactate synthase (budB), and alcohol dehydrogenase (budC) were identified in K. pneumoniae genomic DNA. With the goal of enhancing 2,3-BD production, these genes were cloned into pUC18K expression vectors containing the lacZ promoter and the kanamycin resistance gene to generate plasmids pSB1-7. The plasmids were then introduced into K. pneumoniae using electroporation. All strains were incubated in flask experiments and 2,3-BD production was increased by 60% in recombinant bacteria harboring pSB04 (budA and budB genes), compared with the parental strain K. pneumoniae KCTC2242. The maximum 2,3-BD production level achieved through fedbatch fermentation with K. pneumoniae SGJSB04 was 101.53 g/l over 40 h with a productivity of 2.54 g/l.h. These results suggest that overexpression of 2,3-BD synthesisrelated genes can enhance 2,3-BD production in K. pneumoniae by fermentation.

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The platform chemical 2,3-butanediol (2,3-BDO) is a valuable product that can be converted into several petroleum-based chemicals via simple chemical reactions. Here, we produced 2,3-BDO with the non-pathogenic and rapidly growing Corynebacterium glutamicum. To enhance the 2,3-BDO production capacity of C. glutamicum, we introduced budA encoding acetolactate decarboxylase from Klebsiella pneumoniae, a powerful 2,3-BDO producer. Additionally, budB (encoding α-acetolactate synthase) and budC (encoding acetoin reductase) were introduced from K. pneumoniae to reinforce the carbon flux in the 2,3-BDO production. Because budC had a negative effect on 2,3-BDO production in C. glutamicum, the budB and budA introduced strain, SGSC102, was selected for 2,3-BDO production, and batch culture was performed at 30 °C, 250 rpm and pH 6.86 with pure glucose, molasses, and cassava powder as carbon substrates. After batch culture, significant amount of 2,3-BDO (18.9 and 12.0 g/L, respectively) was produced from 80 g/L of pure glucose and cassava powder.

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meso-2,3-Butanediol (meso-2,3-BDO) is essential for the synthesis of various economically valuable biosynthetic products; however, the production of meso-2,3-BDO from expensive carbon sources is an obstacle for industrial applications. In this study, genes involved in the synthesis of 2,3-BDO in Klebsiella pneumoniae were identified and used to genetically modify Escherichia coli for meso-2,3-BDO production. Two 2,3-BDO biosynthesis genes-budA, encoding acetolactate, and meso-budC, encoding meso-SADH-from K. pneumoniae were cloned into the pUC18 plasmid and introduced into E. coli. In 2 l batch culture, the SGSB03 E. coli strain yielded meso-2,3-BDO at 0.31 g/g(glucose) (with a maximum of 15.7 g/l(culture) after 48 h) and 0.21 g/g(crude glycerol) (with a maximum of 6.9 g/l(culture) after 48 h). Batch cultures were grown under optimized conditions (aerobic, 6% carbon source, 37 °C, and initial pH 7). To find the optimal culture conditions for meso-2,3-BDO production, we evaluated the enzyme activity of meso-SADH and the whole cell conversion yield (meso-2,3-BDO/acetoin) of the E. coli SGSB02, which contains pSB02. meso-SADH showed high enzyme activity at 30-37 °C and pH 7 (30.5-41.5 U/mg of protein), and the conversion yield of SGSB02 E. coli was highest at 37-42 °C and a pH of 7 (0.25-0.28 g( meso-2,3-BDO)/g(acetoin)).