Production of poly(3-hydroxybutyrate) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) by Rhodopseudomonas palustris SP5212

Production of poly(3-hydroxybutyric acid) [P(3HB)] by Rhodopseudomonas palustris SP5212 isolated in this laboratory has been optimized under phototrophic microaerophilic conditions. Cells grown in malate medium accumulated 7.7% (w/w) P(3HB) of cellular dry weight at the early stationary phase of growth. The accumulated P(3HB) however, attained 15% (w/w) of cellular dry weight when acetate (1.0%, w/v) was used as the sole carbon source under nitrogen-limiting conditions. Synthesis and accumulation of polymer was favoured by sulphate-free conditions and at a phosphate concentration sub-optimal for growth. The polymer content of cells was increased drastically (34% of cellular dry weight) when the acetate containing medium was supplemented with n-alkanoic acids. Compositional analysis by H-1 NMR revealed that these accumulated polymers were composed of 3-hydroxybutyric acid and 3-hydroxyvaleric acid (3HV). The contents of 3HV in these copolymers ranged from 14 to 38 mol%.