INDUCTION OF ENCYSTMENT AND POLY-BETA-HYDROXYBUTYRIC ACID PRODUCTION BY AZOTOBACTER-CHROOCOCCUM MAL-201

Azotobacter chroococcum MAL-201, when grown under nitrogen-free condit ions with excess glucose, accumulated poly-beta-hydroxybutyric acid am ounting to 75% of cell dry weight at the late exponential phase. This led to induction of encystment, which increased steadily with concomit ant intracellular degradation of the polymer, Increase in encystment a nd PHB production were parallel up to 0.5% (wt/vol) glucose. Further i ncrease in glucose reduced cyst formation but enhanced PHB accumulatio n. Replacement of glucose by n-butyl alcohol and metabolically related compounds identified crotonate as the best encystment inducer followe d by beta-hydroxybutyrate and butyrate, but PHB production was inhibit ed in general, Supplementation of medium with these compounds enhanced the onset of encystment, and only beta-hydroxybutyrate increased PHB accumulation significantly.