Hyeonsoo Kim

Enhanced production of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) by fed-batch cultures of Pseudomonas sp EL-2

Pseudomonas sp EL-2 was cultivated to produce poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [P(3HB-co-3HV)] from a structurally unrelated carbon source, glucose, by a fed-batch culture technique. Variation of the carbon to nitrogen (C/N) ratio of the medium produced optimal P(3HB-co-3HV) production at a C/N ratio of 95. Production of P(3HB-co-3HV) was favored by a dissolved oxygen tension of 40%. A maximum biomass concentration of 38 g L−1 containing 53% P(3HB-co-3HV) was achieved after 45 h of cultivation. This corresponds to a volumetric productivity of 0.84 g L−1 h−1. The copolymer contained 7.5 mol% 3-hydroxyvalerate. Journal of Industrial Microbiology & Biotechnology (2000) 24, 36–40.

Increased incorporation of gaseous CO2 into succinate by Escherichia coli overexpressing carbonic anhydrase and phosphoenolpyruvate carboxylase genes.

Carbon dioxide (CO2) is an abundant and cheap carbon source that is partly responsible for global warming in the atmosphere. The objective of this study was to construct a recombinant E. coli strain that can show enhanced production of succinate derived from CO2. In this study, we confirmed the enhancement of utilization by analyzing succinate containing one carbon-13 (13C) derived from 13CO2. Firstly, the carbonic anhydrase gene (SP(-)HCCA) derived from Hahella chejuensis KCTC 2396 was over-expressed to enhance carbon flux toward bicarbonate ion (HCO3-) synthesis in E. coli. The phosphoenolpyruvate carboxylase gene (ppc) was over-expressed to enhance the production of oxaloacetate by enhancing the carbon flux. Compared with the control strain, the percentage of the succinate containing one 13C (succinate119) to total succinate was enhanced by approximately 2.80-fold and the amount of succinate119 also increased by approximately 4.09-fold in SGJS120. Secondly, the lactate dehydrogenase gene (ldhA) was deleted to re-direct the utilization of the carbon source from glucose to enhance succinate production in SGJS120. However, ldhA deletion did not increase CO2 utilization in SJGS120. Finally, the phosphotransferase system gene (ptsG) and pyruvate kinase F gene (pykF) were deleted to increase the amount of phosphoenolpyruvate (PEP). SGJS126 (pykF deletion strain) showed the highest increase, which was 6.05-fold higher than the control strain. From the results, SP(-)HCCA overexpression and pykF deletion may be useful for enhancing CO2 utilization in E. coli. Additionally, engineered strains showed the potential to reduce the cost of succinate production by using an industrially cheaper carbon source such as CO2 and converting CO2 to a valuable chemical.