Metabolic Engineering of Eubacterium limosum KIST612 for 2,3-butanediol Production

Abstract

The petroleum refineries are traditional processes for producing chemicals and fuels. There are problematic issues such as the depletion of fossil fuels and negative environmental impacts. As a result, the paradigm has been shifted from petroleum refineries to alternatives, including bio-refineries. The bacteria such as acetogen are utilized in the biological conversion process due to the high potential of chemical production from the source of low carbon materials, including CO and CO2. The Gram-positive, obligately anaerobic, and acetogenic bacterium, Eubacterium limosum KIST612 can produce mainly acetate, lactate, and butyrate. The 2,3butanediol (BDO) is a useful chemical with a variety of applications for industrial needs that can be used as a precursor in manufactures for chemical products including methyl ethyl ketone, butadiene, etc. Based on the genomic sequence analysis, there is a missing enzyme to produce the BDO that is a 2,3-butanediol dehydrogenase (BDH). To construct the complete metabolic pathway for BDO production, the putative BDH-encoding genes from Clostridium autoethanogenum, were heterologously expressed in E. limosum KIST612, respectively. It is also necessary to gain reducing power for the synthesis of 2,3-BDO. By deletion of the lactate production pathway, the flow of carbon and reducing power will be redirected to produce the BDO. To compare the product yields, the mutant strains of E. limosum KIST612 including wild-type were grown on glucose as a substrate.