engleski

1,2-Propanediol production from glycerol via a endogenous pathway of Klebsiella pneumoniae

Klebsiella pneumoniae is an important microorganism and is used as a cell factory for many chemicals production. When glycerol was used as the carbon source, 1, 3-propanediol was the main catabolite of this bacterium. K. pneumoniae ΔtpiA lost the activity of triosephosphate isomerase, and prevented glycerol catabolism through the glycolysis pathway. But this strain still utilize glycerol and 1, 2-propanediol became the main catabolite. Key enzymes of 1, 2- propanediol synthesis from glycerol were investigated in detail. dhaD and gldA encoded glycerol dehydrogenases were both responsible for the conversion of glycerol to dihydroxyacetone, but overexpression of the two enzymes result in a decrease of 1, 2-propanediol production. There are two dihydroxyacetone kinases (I and II), but the dihydroxyacetone kinase I had no contribution to dihydroxyacetone phosphate formation. Dihydroxyacetone phosphate was converted to methylglyoxal, and methylglyoxal was then reduced to lactaldehyde or hydroxyacetone and further reduced to form 1, 2-propanediol. Individual overexpression of mgsA, yqhD, and fucO all resulted in increased production of 1, 2- propanediol, but only the combined expression of mgsA and yqhD showed a positive effect on 1, 2- propanediol production. The process parameters for 1, 2-propanediol production by Kp ΔtpiA-mgsA-yqhD were optimized, with pH 7.0 and agitation rate of 350 rpm were found to be optimal. In the fed-batch fermentation, 9.3 g/L of 1, 2-propanediol was produced after 144 hours of cultivation and the substrate conversion ratio was 0.2 g/g. This study provides an efficient way of 1, 2-propanediol production from glycerol via an endogenous pathway of K. pneumoniae.

1, 2-propanediol ; glycerol ; tpiA ; mgsA ; Klebsiella pneumoniae

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