Effects of culture conditions on the composition of poly(3-hydroxybutyrate-co-4-hydroxybutyrate) synthesized by Comamonas acidovorans

Poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3HB-co-4HB)] copolymers containing 0–96 mol% 4HB monomers were produced by Comamonas acidovorans when cultivated on a mixture of glucose and 1,4-butanediol. In addition up to 53 wt.% of the dry cell weight (DCW) poly(3-hydroxybutyrate) [P(3HB)] was accumulated from two-stage cultures using glucose as the sole carbon source. This large accumulation of P(3HB) was achieved because glucose was also added to the first-stage of cell biomass production. Glucose addition to the first-stage did not result in significant accumulation of P(3HB) in the first-stage (<2 wt.% of the DCW) but is probably important in the induction of enzymes involved in glucose uptake and metabolism. By employing this strategy of glucose induction it is shown that C. acidovorans can produce more than 40 wt.% of the DCW P(3HB-co-4HB) from a mixture of glucose and 1,4-butanediol in two-stage cultivation. The copolymer composition can further be controlled by changing the concentrations of the carbon sources. In addition, factors such as pH, inoculum concentration and aeration significantly affected the composition of P(3HB-co-4HB).