Studies On Improving The Production And Properties Of PHB Produced By The Strain G-Ⅲy

The fermentation condition and culture condition for the strain G-IIIy producing poly- β -hydroxyalkanoate acid were optimized. The best fed-batch culture conditions were as follow: 2.1% original sugar concentration, 0.07% original ammonium sulfate concentration, 1.5-2.0% sugar concentration controlled in the course of fermentation, nitrogen source feeding stopped at fermentation for 20 hours. Better results could be obtained, For 40 hours fermentation, cell dry weight and PHB concentration reached 32.7 g · L-1 and 21.4g · L-1 respectively.The synthesis of Poly ( β -Hydroxybutyrate-co-β-Hydroxyvalerate) by the strain G-IIIy from different precusor was studied. It was found that the strain G-IIIy could accumulate PHBV with sucrose as carbon source and propionic acid or valeric acid as precursor . In 2L self-controlled fermentor, the dry cell weight, PHBV concentration and PHBV content reached 35.8g·L-1, 22.6g·L-1 and 38.4% respectively in the case of fermentation for 42 hours and the propionic acid as precursor. Through the GC analyses and the nuclear magnetic resonance analyses showed that the copolyesters obtained here were random copolymers of 3HB and 3HV units. HV fraction in the copolymers reached 38%. Through thermal analyses showed that the melting point was reduced and pyrolysis temperature was increased.Based on the studies of above mentioned mainly, experimented 10L fermentor supplement medium magnified experiment and the result was 37.7 g · L-1 desiccated cellmass and 25.27 g · L-1 PHBV yield. This had significance to the industrial production of PHBV by the strain G-ffly.