BIOSYNTHESIS OF COPOLYESTERS BY HYDROGENOPHAGA-PSEUDOFLAVA FROM VARIOUS LACTONES

Hydrogenophaga pseudoflava (formerly Pseudomonas pseudoflava) was able to accumulate a large amount of copolyesters when grown on mixed subs trates of glucose and lactones in a batch fermentation. Lactones such as gamma-butyrolactone, gamma-valerolactone, and higher analogues gene rally did not support cell growth when used as the sole carbon source. Go-feeding of lactones with glucose enhanced the utilization of lacto nes for both copolyester accumulation and cell growth. The copolyester from the cells grown on the mixed substrates of glucose (10 g/L) and gamma-valerolactone (1-3 mL/L) was poly(3-hydroxybutyrate-co-3-hydroxy valerate) (P(3HB-co-3HV)), while cells grown with gamma-butyrolactone (1-3 mL/L) as a cosubstrate produced poly(3-hydroxybulyrate-co-4-hydro xybutyrate) (P(3HB-co-4HB)). The values of parameter D, calculated fro m the NMR dyad-sequence data for polymer samples obtained after 72 h o f cultivation, showed lactone concentration dependences differing amon g lactones. The timecourse data obtained from growth on the cosubstrat es of gamma-valerolactone (2 mL/L) and glucose (10 g/L) revealed that 3HV-rich copolymers were synthesized in the early growth phase, and th e 3HB-rich fraction steadily increased in the later accumulation phase and then peaked at 80 h when gamma-valerolactone was depleted. These polyhydroxyalkanoate accumulation profiles suggested a high D value of the Final product, whose value was determined to be 3.25. gamma-Valer olactone was consumed faster than gamma-butyrolactone. The difference between the assimilation behavior of the two lactones was discussed in relation to the heterogeneity of the final copolyester products. A co rrelation between NMR microstructure and the physiology of polyhydroxy alkanoate accumulation was observed.