Optimization of Process Parameters for Maximum Poly(-$-)hydroxybutyrate (PHB) Production by Bacillus thuringiensis IAM 12077 ADWITIYA PAL, ASHWINI PRABHU, AVINASH ARUN KUMAR, BADRI RAJAGOPAL, KAJAL DADHE, VOMSI PONNAMMA and SRIVIDYA SHIVAKUMAR*

The study aimed at screening and identifying a potential poly-$-hydroxybutyrate (PHB) accumulating Bacillus strain and optimization of media parameters for increased PHB production by the strain. A Gram-positive bacterium that accumulated PHB was isolated from local garden soil of Bangalore. Based on morphological and physiological properties, and nucleotide sequence (about 1.5 kb) of its 16S rDNA it was identified as Bacillus thuringiensis IAM 12077. PHB production was found to be comparable to most of the Bacillus sp. reported to date. PHB production by this strain was dependent on nutrient limitation. Cell dry weight and PHB accumulation increased significantly under biphasic growth condition (from nutrient broth to nitrogen-deficient medium) as compared with growth in nutrient broth alone (from 0.32 g/l to 2.76 g/l cell dry weight; 24% to 43.37% PHB accumulation; 0.2 g/l to 1.2 g/l PHB production), with maximum accumulation at 24 h in nitrogen-deficient medium. Time course study of growth and PHB production by this strain in the nitrogen deficient medium showed that PHB production was associated with the stationary phase of growth. All the tested media containing different carbon and nitrogen sources supported growth and PHB production. Ultraviolet spectrum of the extracted polymer showed a characteristic peak at 235 nm. K e y w o r d s: Bacillus sp., biphasic studies, carbon and nitrogen sources, fermentation kinetics, Poly(-$-)hydroxybutyrate * Corresponding author: S. Srividya, Department of Microbiology, Center for PG Studies, SBM Jain College, 18/3, 9th Main, 3rd block Jayanagar, Bangalore-560011; phone: (+91) 080 41210691; fax: (+91) 080 41210692; e-mail: [email protected] 150 Adwitiya Pal et al. 2 and Prabakaran, 2006). In this paper we report the PHB accumulation ability by Bacillus thuringiensis IAM 12077 and also describe the influence of nutritional conditions on its growth and PHB accumulation.