budC knockout in Klebsiella pneumoniae for bioconversion from glycerol to 1,3-propanediol

Abstract

2,3-Butanediol (2,3-BD) is a major by-product of 1,3-propanediol (1,3-PDO) fermentation by Klebsiella pneumoniae ZG25. It not only consumes large amounts of its carbon source and nicotinamide adenine dinucleotide to diminish synthesis of 1,3-PDO, but also serves as an obstacle to high-purity 1,3-PDO in downstream processes. To decrease the formation of 2,3-BD and make an intrinsic improvement in 1,3-PDO production, the budC gene in K. pneumoniae, coding 2,3-BD dehydrogenase, which is a key gene of the 2,3-BD pathway, was successfully knocked out using the Red recombination system described in this paper. The results of the mutant fed-batch fermentation showed that the 1,3-PDO concentration, productivity per cell dry weight, and conversion rate increased to 880 mmol L(-1) , 22.0 mmol L(-1) h(-1) , and 0.700 mol mol(-1) , respectively, increasing by 10%, 15%, and 11% compared with the parent strain. Meanwhile, 2,3-BD was still found in fermentation broth with the 2,3-BD metabolic pathway blocked, which implies that K. pneumoniae possesses a pathway of the 2,3-BD cycle as a replenishment pathway.

Keywords: 1,3-propanediol; 2,3-BD cycle; 2,3-BD dehydrogenase; 2,3-butanediol; Klebsiella pneumoniae; Red recombination system.