Biosynthesis of poly(3-hydroxypropionate) from glycerol using engineered Klebsiella pneumoniaestrain without vitamin B12

Poly(3-hydroxypropionate) (P3HP) is a biodegradable and biocompatible thermoplastic. Previous studies demonstrated that engineered Escherichia colistrains can produce P3HP with supplementation of expensive vitamin B12. The present study examined the production of P3HP from glycerol in the recombinant Klebsiella pneumoniaestrain, which naturally synthesizes vitamin B12. The genes glycerol dehydratase and its reactivation factor (dhaB123, gdrA,and gdrBfrom K. pneumoniae), aldehyde dehydrogenase (aldHfrom E. coli) were cloned and expressed in K. pneumoniaeto produce 3-hydroxypropionate (3HP), with 2 genes (dhaTand yqhD) for biosynthesis of 1,3-propanediol were deleted. To obtain P3HP production, propionyl-CoA synthetase (prpEfrom E. coli) and polyhydroxyalkanoate synthase (phaCfrom Ralstonia eutropha) were introduced. Under the appropriate aeration condition, the cell yield and P3HP content were 0.24 g/L and 12.7% (wt/wt [cell dry weight]) respectively along with 2.03 g/L 3HP after 48 h cultivation. Although the yield is relatively low, this study shows the feasibility of producing P3HP in K. pneumoniaefrom glycerol without vitamin B12for the first time. The results also suggest that the aeration conditions should be optimized carefully for the efficient production of P3HP.