Construction Of Novel Recombinant Escherichia Coli Capable Of Producing 1, 3-propanediol And Its Conversion Of Glycerol

1,3-Propanediol has numerous applications in the manufacture of polymers, foods, lubricants, and medicines. Industrial 1,3-propanediol production has attracted attention as an important monomer to synthesize a new type of polyester, polytrimethylene terephthalate. 1,3-Propanediol is produced by two methods: chemical synthesis and microbial conversion. However, traditional chemical conversion of 1,3-propanediol is difficult, which has a low selectivity and consequently its high price hinders the utilization of 1,3-propanediol in polymer industries. Interest has now been focused on the production of 1,3-propanediol by recombinant strain fermentation. The overall goal of this research was to construct a recombinant strain which could convert glycerol to 1,3-propanediol with high titers. The structure gene yqhD from a wild-type Escherichia coli encoding 1,3-propanediol oxidoreductase isoenzyme and the structure gene dhaB from Citrobacter freundii encoding glycerol dehydratase were amplified by using PCR method. The expression vector pUCtac harboring yqhD gene and dhaB gene was transformed into E. coli JM109 to yield the recombinant strain E. coli JM109 (pUCtac-dhaB-yqhD). Fermentation experiments were performed by E. coli JM109, E. coli JM109(pEtac-yqhD), E. coli JM109(pUCtac-dhaB), E. coli JM109(pUCtac -dhaB-dhaT), E. coli JM109(pUCtac-dhaB-yqhD) and C. freundii. Results showed that no 1,3-propanediol was produced when recombinant strain harboring neither dhaB gene nor yqhD gene, only the strain harboring both dhaB gene and yqhD gene converted 50 g/L glycerol to 28.0 g/L 1,3-propanediol after induction by IPTG.Comparing with other E. coli JM109(pUCtac-dhaB-dhaT), E. coli JM109 (pUCtac-dhaB-yqhD) could convert glycerol to 1,3-propanediol with higher titers, However, the inducer of pUCtac was IPTG, IPTG was usually used in the laboratory scale, since its high price and it had to be added in large amounts to the culture to sustain high expression level of the recombinant protein, limiting its potential application in the industry scale. So the temperature control vector pHsh was firstly employed as expression vector for recombinant strain construction in this study.Comparing with other recombinant strain induced by IPTG, there were no significantly difference in 1,3-propanediol yield by recombinant strain induced by temperature. The yield of 1,3-propanediol on 50 g/L glycerol by E. coli JM109(pUCtac-dhaB-yqhD) was 56.8 % and the yield of 1,3-propanediol by E. coli JM109(pHsh-dhaB-yqhD) was 53.0 % after induction.Our experiments demonstrated that the coenzyme B12-dependent glycerol...