Metabolic Engineering of Klebsiella Oxytoca Strain to Enhance (R,R)-2,3-Butanediol Production

2,3-butanediol exists in three types of stereoisomoers, (R,R)-BD, (S,S)-BD, and meso-BD, and each stereoisomer has different physiochemical properties. meso and (R,R)-2,3-BD have similar applicability in chemical industry sectors, such as 1,3-butadiene and methyl ethyl ketone. However, their applications are strongly limited to some special sectors by their different physiochemical properties. meso-2,3-BD is applicable to a component of cosmetics as an moistening agent. Only (R,R)-2,3-BD has an applicability in agricultural industry, which is to activate plants’ own defense systems. Natural Klebsiella oxytoca mainly produces meso-2,3-BD (> 90% of total 2,3-BD). In order to expand the potential applications of K. oxytoca strain, we engineered the metabolism of K. oxytoca strain. We introduced an exogenous gene encoding (R,R)-2,3-BD dehydrogenase from Paenibacillus polymyxa into the site of budC gene in K. oxytoca strain and increased the expression of of (R,R)-2,3-BD dehydrogenase further. The final strain could produce up to 106.7 g/L of (R,R)-2,3-BD [meso-2,3-BD, 9.3 g/L] in fed-batch fermentation, with a productivity of 3.1 g/L/h and a yield of 0.40 g/g. [This work was supported by the Industrial Strategic Technology Development Program (No. 10050407) funded by the Ministry of Trade, Industry & Energy (MOTIE, Korea).]