Utilization of oxidative pressure for enhanced production of poly-beta-hydroxybutyrate and poly(3-hydroxybutyrate-3-hydroxyvalerate) in Ralstonia eutropha

Ralstonia eutropha was cultivated under oxidative conditions in the presenc e of hydrogen peroxide and methyl viologen to stimulate the flux of NADPH t o the PHA biosynthesis pathway. The effects of oxidants on the biosynthesis of poly-beta -hydroxybutyrate(PHB) and poly(3-hydroxybutyrate-3-hydroxyval erate 3HV)] were investigated. The biosynthesis rate and concentrations of PHB and its copolymer P(3HB-3HV) increased significantly under the oxidativ e pressure of methyl viologen, meanwhile, the molar fraction of 3HV in P(3H B-3HV) remained constant. The effect of methyl viologen on the Bur of the i ntermediate compounds was investigated by measuring the activity of enzymes related to PHB biosynthesis, glucose 6-phosphate dehydrogenase (G6PD), and NADPH level. The oxidant significantly activated the G6PD of R. eutropha, increasing the NADPH level used for the reduction reaction of acetoacetyl-C oA to beta -hydroxybutyryl-CoA, thereby enhancing the biosynthesis of PHB a nd P(3HB-3HV).