Production of Poly(hydroxybutyrate) Homopolymer and Copolymer from Ethanol and Propanol in a Fed‐Batch Culture

Production of poly (hydroxy butyrate) (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‐o1 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‐o1 in the feed and reached a maximum of 35.2 mol % from pure propan‐1‐o1. Gradual oxygen limitation during the late log phase induced 21.9% PHB by weight.