NUTRITIONAL AND CULTURAL CONDITIONS FOR PRODUCTION OF POLY-3-HYDROXYBUTYRIC ACID BY AZOTOBACTER-CHROOCOCCUM

Free-living nitrogen-fixing bacteria have been identified as a potenti al source of poly-3-hydroxybutyric acid (PHB). Systematic study of thi s ability of N-2-fixing organisms has lead to the isolation of an effi cient strain, identified as Azotobacter chroococcum. Nutritional requi rements and cultural conditions for optimal production of PHB by this strain under laboratory conditions were determined. In N-free liquid m edium containing 2 % glucose, the strain accumulated PHB up to 68 % of its cell dry mass. Glucose and mannitol were found to be the best car bon sources, while organic nitrogen compounds were preferred as nitrog en source. Maximum yield (3.3 g/L) was obtained with 0.2 % bactopepton e supplementation. Inorganic phosphate at a concentration suboptimal f or growth had some growth-promoting effect. Under oxygen limiting cond itions, biomass production was enhanced but a different response was o btained for PHB production.