PRODUCTION OF POLY(HYDROXYBUTYRATE) HOMOPOLYMER AND COPOLYMER FROM ETHANOL AND PROPANOL IN A FED-BATCH CULTURE

Production of poly(hydroxybutyrate) (PHB) homopolymer and poly(hydroxybutyrate-valerate) (PHBV) copolymer by a mutant strain of Alcaligenes eutrophus was studied in a 7-L fed-batch fermentor using ethanol and propan-1-ol as sole carbon sources. Decreasing the initial phosphate concentration to 20 % of the original Repaske medium allowed exhaustion of the phosphate during logarithmic growth and was an effective means of PHB(V) induction. Up to 74 % PHB by weight was obtained with 63 g/L of dry cell mass. The copolymer content increased with a higher fraction of propan-1-ol in the feed and reached a maximum of 35.2 mol % from pure propan-1-ol. Gradual oxygen limitation during the late log phase induced 21.9 % PHB by weight.