Klebsiella Pneumoniae Reconstruction Of Producing 1,3-propanediol

As an important chemical raw material,1,3-propanediol (1,3-PD) has been widely used in the field of printing and dyeing, paint, ink, drugs, antifreeze, lubricants. Moreover, it has been attracted much attention as a monomer in constituting PTT (polyethylene terephthalate). There are two methods in produce 1,3-PD-chemical synthesis and microbial fermentation. Nowadays, due to the shortage of petrochemical resources, microbial fermentation becomes a hot research at home and abroad.Production of 1,3-propanediol from glycerol by Klebsiella pneumoniae is restrained by lactate formation. The increase of lactate in the broth can inhibit cell growth and reduce 1,3-propanediol conversion rate.The lactate dehydrogenase gene (IdhA) of production lactate by Klebsiella pneumoniae was modified by λ,Red recombination system. One 300bp homologous recombinant fragment:ldhAl-Cmr-ldhA2 was constructed for the gene knockout. After resistance experiments, PCR determination, K. pneumonial-1ΔldhA with IdhA gene knocked out obtained by λRed recombination. After 24h fermentation,the maximum yield of lactate was reduced to 0.49g/L from 10.16g/L and the maximum threonine yield of 1,3-propanediol was increased to 85.76g/L from 78.83g/L,comparing with that of the original strain K.pneumonia2-1. The conversation rate of glycerol was improved to 65.97% from 60.64%, increasing by 5.33%.Meantime,production of 1,3-propanediol from glycerol by Klebsiella pneumoniae is restrained by ethanol formation. The increase of ethanol in the broth can inhibit cell growth and reduce 1,3-propanediol conversion rate.The acetaldehyde dehydrogenase gene (aldH) of production ethanol by Klebsiella pneumoniae was modified by λRed recombination system. One 300bp homologous recombinant fragment:aldHl-Cmr-aldH2 was constructed for the gene knockout. After resistance experiments, PCR determination, K. pneumonia2-Δ aldH with aldH gene knocked out obtained by λRed recombination. After 24h fermentation,the maximum yield of ethanol was reduced to 0.47g/L from 7.24g/L and the maximum threonine yield of 1,3-propanediol was increased to 82.55g/L from 78.83g/L,comparing with that of the original strain K.pneumonia2-1. The conversation rate of glycerol was improved to63.50% from 60.64%, increasing by 2.86%.