Improving 1,3-Propanediol Production from Glycerol in a Metabolically Engineered Escherichia coliby Reducing Accumulation of sn-Glycerol-3-phosphate

• Published in: Biotechnology progress Vol. 18; no. 4; pp. 694 - 699
• Main Authors: Zhu, Marie M., Lawman, Patricia D., Cameron, Douglas C.
• Format: Journal Article
• Language: English
• Published: USA American Chemical Society 2002
• ISSN: 8756-7938; 1520-6033
• DOI: 10.1021/bp020281

High levels of glycerol significantly inhibit cell growth and 1,3‐propanediol (1,3‐PD) production in anaerobic glycerol fermentation by genetically engineered Escherichia coli( E. coli) strains expressing genes from the Klebsiella pneumoniae dha( K.pneumoniae) regulon. We have previously demonstrated that 1,3‐PD production by the engineered E. colican be improved by reducing the accumulation of methylglyoxal. This study focuses on investigation of another lesser‐known metabolite in the pathways related to 1,3‐PD production‐glycerol‐3‐phosphate (G3P). When grown anaerobically on glycerol in the absence of an exogenous acceptor, the engineered E.colistrains have intracellular G3P levels that are significantly higher than those in K. pneumoniae, a natural 1,3‐PD producer. Furthermore, in the engineered E. colistrains, the G3P levels increase with increasing glycerol concentrations, whereas, in K. pneumoniae, the concentrations of G3P remain relatively constant. Addition of fumarate, which can stimulate activity of anaerobic G3P dehydrogenase, into the fermentation medium led to a greater than 30‐fold increase in the specific activity of anaerobic G3P dehydrogenase and a significant decrease in concentrations of intracellular G3P and resulted in better cell growth and an improved production of 1,3‐PD. This indicates that the low activity of G3P dehydrogenase in the absence of an exogenous electron acceptor is one of the reasons for G3P accumulation. In addition, spent media from E. coliLin61, a glycerol kinase (responsible for conversion of glycerol to G3P) mutant, contains greatly decreased concentrations of G3P and shows improved production of 1,3‐PD (by 2.5‐fold), when compared to media from its parent strain E. coliK10. This further suggests that G3P accumulation is one of the reasons for the inhibition of 1,3‐PD production during anaerobic fermentation.