PRODUCTION OF POLY-BETA-HYDROXYBUTYRATE IN ACINETOBACTER SPP ISOLATED FROM ACTIVATED-SLUDGE

Two strains of Acinetobacter sp. isolated from activated sludge actively removing phosphate were examined for their abilities to produce poly-beta-hydroxybutyrate (PHB). When yield-limited by phosphate, strain RA3117 contained material that stained with Sudan Black, but contained only 0.9% PHB on a dry weight basis. This strain contained no sudanophilic material or PHB when limited by ammonia or sulphate. When strain RA3757 was limited by phosphate, ammonia or sulphate it produced 2.0, 7.8 and 11.5% PHB, respectively, on a dry weight basis. Beta-Ketothiolase and acetoacetyl-coenzyme A (CoA) reductase were only observed in RA3757 cell-free extracts. Beta-Ketothiolase was produced both in cells with and without PHB whereas acetoacetyl-CoA reductase was found only in cells accumulating PHB. When RA3757 was grown in ammonia-limiting medium with acetate, butyrate, caproate or ethanol as carbon source, similar levels of PHB were produced. When cells were grown on valerate, RA3757 produced 5.6 poly-beta-hydroxyvalerate and 0.9% PHB on a dry weight basis.