Moderate overexpression of <i>dhaB</i> through genomic integration improves 1,3-propanediol production by <i>Klebsiella pneumoniae</i>

Abstract Aims Glycerol dehydratase, encoded by dhaB, has been identified as the rate-limiting enzyme for biosynthesis of 1,3-propanediol (1,3-PDO). This study aimed to enhance the production of 1,3-PDO in Klebsiella pneumoniae by increasing the expression of dhaB. Methods and Results Plasmid-based and genomic integration systems for increasing the expression of dhaB were compared. The results showed that plasmid-promoted overexpression of dhaB resulted in growth inhibition, and no inhibition of cell growth was observed by overexpression of dhaB through genomic integration. However, overexpression by genomic integration, even though the copy number was higher, failed to increase 1,3-PDO production. Based on our data, the 1,3-PDO production was stimulated by moderate expression of dhaB through genomic integration. And then, increasing the supply of NADH improved the yield and production of 1,3-PDO from glycerol in K. pneumoniae to 0.71 mol/mol and 81 g/L respectively during a 2-L fed-batch fermentation process. Conclusions Moderate overexpression of dhaB through genomic integration stimulated production of 1,3-PDO by K. pneumoniae.