Study On Mutation Breeding And Optimize Fermentation Conditions For Poly-hydroxybutyrate Acid (PHA) Overproductive Strains

Poly-hydroxybutyrate acid(PHA) is well know as a kind of thermoplastic aliphatic polyster that is synthesized and accumulated intracellularly during unbalanced growth by microorganism.Nowadays,PHA have attracted increasing interest as an alternative to petroleum-derived plastics for its similar mechanical properties to those of polypropylene,as well as its additional advantage of being completely biodegradable,biocompatible, non-toxicity and etc.As a new kind of biodegradable plastic,PHA has been produced by biological ferment presently.So far,many research focused on separating valuable strains which can produce PHA,producing srains through compound mutation,and sudying on the optimizational fermentation conditions.We Compound mutation to producing-srains from Y-4 which conserved by our laboratory,then study on the optimizational fermentation conditions of overproductive strains in order to provide a new overproductive strain for industrialization. Following results have been obtained in this study.The Mutation strain is attained by UV and He-Ne laser.The desiccated cellmass from BY- 120-30 was 13.2g/L enhancing 43.5%;PHA yield from BY-120-30 was 7.0 g/L enhancing 55.6%;PHA production ratio from BY-120-30 was 53.0%enhancing 8.4%.Experimentized the shake bottle fermentation optimization and the best supplemented medium fermentation condition was as follow:2.5%cane sugar,0.3%proteose peptone, 0.3%yeast extract,0.3%(NH₄)₂SO₄,0.5%NaCl,initial pH=7,10%inoculation amount, liquid capacity 70mL in 250mL flask,at temperature of 30℃,with 220 revolutions per minute.Supplemented 6mmol/L H₂O₂ at 12h,desiccated cellmass was 15.8 g/L,PHA yield was 9.7 g/L,PHA production ratio was 61.4%.