Production of poly-β-hydroxybutyrate and measurement of related enzyme activities in Alcaligenes eutrophus

Abstract

Activities of β-ketothiolase (KT) and glucose-6-phosphate dehydrogenase (GPDH) were determined during the fermentation of Alcaligenes eutrophus NCIMB 11599 at three different values of C/N ratio. As the C/N ratio increased the cell growth decreased due to the limitation of nitrogen, while the cellular poly-β-hydroxybutyrate (PHB) content increased. At an initial C/N ratio of 32.8, the cellular PHB content reached 90.0% after 32 h cultivation. The specific activity of β-ketothiolase in each fermentation was the highest immediately after exhaustion of the nitrogen source. Specific activities of β-ketothiolase and glucose-6-phosphate dehydrogenase were maintained stably within the tested range of C/N ratio even after the N-source was completely exhausted.