Lactic Acid Containing Polymers Produced in EngineeredSinorhizobium melilotiandPseudomonas putida

This study demonstrates that novel polymer production can be achieved by introducing pTAM, a broad-host-range plasmid expressing codon-optimized genes encoding Clostridium propionicum propionate CoA transferase (Pct Cp ) and a modified Pseudomonas sp. MBEL 6-19 polyhydroxyalkanoate (PHA) synthase 1 (PhaC1 Ps6-19 ), into phaC mutant strains of the native polymer producers Sinorhizobium meliloti and Pseudomonas putida . Both phenotypic analysis and gas chromatography analysis indicated the synthesis and accumulation of biopolymers in S. meliloti and P. putida strains. Expression in S. meliloti resulted in the production of PLA homopolymer up to 3.2% dried cell weight (DCW). The quaterpolymer P(3HB- co -LA- co -3HHx- co -3HO) was produced by expression in P. putida . The P. putida phaC mutant strain produced this type of polymer the most efficiently with polymer content of 42% DCW when cultured in defined media with the addition of sodium octanoate, while the greatest LA fraction (4% mol) was achieved in the same strain cultured in LB with the addition of lactic acid. This is the first report, to our knowledge, of the production of a range of different biopolymers using the same plasmid-based system in different backgrounds. In addition, it is the first time that the novel polymer (P(3HB- co -LA- co -3HHx- co -3HO)), has been reported being produced in bacteria.