Microbial production of lactate-containing polyhydroxyalkanoates(PHAs) using metabolically engineered Escherichia coli

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Jung Eun Yang, Yu Kyung Jung, Tae Yong Kim, Si Jae Park, Sang Yup Lee

KAIST, South Korea

Polylactic acid (PLA) has been considered an environmentally good alternative to petroleum-based plastic because it possesses several desirable properties such as biocompatibility, biodegradability, and non-toxic to human. 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 reported the production of PLA and its copolymer, poly(3-hydroxybutyrate-co-lactate), by direct fermentation of metabolically engineered E. coli. In this study, the metabolic pathways of E. coli were further engineered based on in silico genome-scale metabolic flux analysis. By using this engineered strain, PLA homopolymer and P(3HB-co-LA) copolymers containing up to 70mol% lactate could be produced up to 11wt% and 46wt% 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 Technology Development Program to Solve Climate Changes (systems metabolic engineering for biorefineries) from the Ministry of Education, Science and Technology (MEST) through the National Research Foundation of Korea (NRF-2012-C1AAA001-2012M1A2A2026556).]