POLY-beta-HYDROXYBUTYRATE (PHB) PRODUCTION BY Bacillus sp. ISOLATED FROM SOIL

Abstract

Petrochemical-derived nondegradable plastics accumulate in the environment in large quantities. Biopolymeric materials such as microbial poly-beta-hydroxybutyrate (PHB) are, in contrast to chemically synthesized plastics, biodegradable in nature. PHB is synthesized by bacteria as energy and carbon storage material. Of the Bacillus spp. strains isolated from soil, three strains (B20, B23 and B35) were selected to study biosynthesis of PHB in detail. To identify strains B20, B23 and B35, morphological and physiological characterizations were used. In order to maximize the PHB productivity of these bacteria, utilization of different carbon sources by three strains, growth rate and dry-cell weight (DCW) were investigated in the existence of ammonium sulfate which was used as the nitrogen source. These strains could utilize a variety of different carbons for the synthesis of PHB. It was observed that the strains achieved the highest growth rates (0.33-0.82 by OD660) and the best PHB productivity (2.90-6.25 g/L) on glucose). A relatively high yield of PHB was obtained in these wild strains especially in B35; hence, these strains were considered as potent organisms for industrial application.