Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
6494439 | Metabolic Engineering | 2015 | 9 Pages |
Abstract
Biotechnological production of biofuels is restricted by toxicity of the products such as ethanol and butanol. As its low toxicity to microbes, 2,3-butanediol (2,3-BD), a fuel and platform bio-chemical, could be a promising alternative for biofuel production from renewable bioresources. In addition, no bacterial strains have been reported to produce enantiopure 2,3-BD using lignocellulosic hydrolysates. In this study, Enterobacter cloacae strain SDM was systematically and metabolically engineered to construct an efficient biocatalyst for production of the fuel and enantiopure bio-chemical-(2R,3R)-2,3-BD. First, the various (2R,3R)-2,3-BD dehydrogenase encoding genes were expressed in a meso-2,3-BD dehydrogenase encoding gene disrupted E. cloacae strain under native promoter Pb of the 2,3-BD biosynthetic gene cluster of E. cloacae. Then, carbon catabolite repression was eliminated via inactivation of the glucose transporter encoding gene ptsG and overexpression of a galactose permease encoding gene galP. The resultant strain could utilize glucose and xylose simultaneously. To improve the efficiency of (2R,3R)-2,3-BD production, the byproduct-producing genes (ldh and frdA) were knocked out, thereby enhancing the yield of (2R,3R)-2,3-BD by 16.5% in 500-mL Erlenmeyer flasks. By using fed-batch fermentation in a 5-L bioreactor, 152.0Â g/L (2R,3R)-2,3-BD (purity>97.5%) was produced within 44Â h with a specific productivity of 3.5Â g/[LÂ h] and a yield of 97.7% from a mixture of glucose and xylose, two major carbohydrate components in lignocellulosic hydrolysates. In addition, when a lignocellulosic hydrolysate was used as the substrate, 119.4Â g/L (2R,3R)-2,3-BD (purity>96.0%) was produced within 51Â h with a productivity of 2.3Â g/[LÂ h] and a yield of 95.0%. These results show that the highest records have been acquired for enantiopure (2R,3R)-2,3-BD production by a native or engineered strain from biomass-derived sugars. In addition to producing the 2,3-BD, our systematic approach might also be used in the production of other important chemicals by using lignocellulose-derived sugars.
Keywords
Related Topics
Physical Sciences and Engineering
Chemical Engineering
Bioengineering
Authors
Lixiang Li, Kun Li, Yu Wang, Chao Chen, Youqiang Xu, Lijie Zhang, Binbin Han, Chao Gao, Fei Tao, Cuiqing Ma, Ping Xu,