Monday, July 25, 2011
Grand Ballroom, 5th fl (Sheraton New Orleans)
Polylactic acid (PLA) has been considered as a good alternative to petroleum-based plastic as it possesses several desirable properties such as biocompatibility, biodegradability, and compostability. PLA is a promising biomass-derived polymer, but is currently synthesized by a two-step process: fermentative production of lactic acid followed by chemical polymerization. Here we report production of PLA homopolymer and its copolymer, poly(3-hydroxybutyrate-co-lactate), by direct fermentation of metabolically engineered E. coli. Introduction of the heterologous metabolic pathways involving engineered propionate CoA-transferase and polyhydroxyalkanoate synthase allowed synthesis of PLA and P(3HB-co-LA) in E. coli, but at relatively low efficiency. In this study, the metabolic pathways of E. coli were further engineered based on in silico genome-scale metabolic flux analysis. Using this engineered strain, PLA homopolymer and P(3HB-co-LA) copolymers containing up to 70 mol% lactate could be produced up to 11 wt% and 46 wt% from glucose, respectively. Thus, the strategy of combined systems-level metabolic engineering and enzyme engineering allowed efficient bio-based one-step production of PLA and its copolymers. [This work was supported by the Korean Systems Biology Research Project (20110002149) of the Ministry of Education, Science and Technology (MEST) through the National Research Foundation of Korea. Further support by the World Class University Program (R32-2008-000-10142-0) through the National Research Foundation of Korea funded by the MEST is appreciated.]