SCREENING AND OPTIMIZATION OF POLY-beta-HYDROXYBUTYRATE (PHB) PRODUCTION BY CERTAIN BACTERIA ISOLATED FROM SOIL

Polyhydroxybutyrates (PHB) are bacterial plastic that can replace the petroleum-based plastic. Many bacteria have the ability to synthesize PHB as intracellular granules. PHB granules are water insoluble, relatively resistant to hydrolytic degradation biocompatible and nontoxic. It has a good oxygen permeability and ultra-violet resistance. Therefore, PHB have many useful applications in the manufacture of packaging containers, bottles, wrapping films, bags and so forth. The aim of this study is to evaluate the PHB yield of Bacillus sp., Pseudomonas sp. and Azotobacter sp. isolated from different garden soils. Besides, PHB productivity was optimized using various carbon, nitrogen sources, temperature and pH. Among total 121 isolates, 42 isolates have synthesized PHB. The results showed that the highest PHB production was with glucose (0.219 gL(-1)) as carbon source, glycine (0.212 gL(-1)) and peptone (0.206 gL(-1)) as nitrogen source, with a temperature of 30 degrees C (0.215 gL(-1)) and at 7.0 of pH (0.206 gL(-1)) by Azotobacter sp. A18.