Modification of substrate and product transport systems in Klebsiella pneumoniae to improve 1,3-propanediol production.

Substrate uptake and product export are important for microbial growth and product synthesis. Here, the glycerol uptake facilitator (GlpF) and the members of the resistance-nodulation-cell division (RND) type efflux system were overexpressed in Klebsiella pneumoniae to promote 1,3-propanediol (1,3-PDO) production. Overexpression of the endogenous K. pneumoniae GlpF improved glycerol dehydratase (GDHt) activity and promoted 1,3-PDO titer from 55.6 to 65.1 g/l. RND members AcrA and the AcrE had no impact on 1,3-PDO production. RND members AcrF and the TolC increased 1,3-PDO titer from 55.6 to 68.4 g/l and 65.4 g/l, respectively. MexB significantly decreased GDHt activity and 1,3-PDO titer. Notably, MexF dramatically enhanced GDHt activity and promoted 1,3-PDO titer and glycerol conversion rate to 74.0 g/l and 0.62 mol/mol, respectively. However, coexpression of the endogenous GlpF and MexF did not further improve 1,3-PDO production. The results present here provided novel information about the applications of the uptake of glycerol and the efflux of 1,3-PDO.