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Pak. J. Bot., 48(1): 349-356, 2016.

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PRODUCTION AND CHARACTERIZATION OF A THERMOSTABLE BIOPLASTIC (POLY-s-HYDROXYBUTYRATE) FROM BACILLUS CEREUS NRRL-B-3711

ASAD-UR-REHMAN*, ALIA ASLAM, RUSHDA MASOOD, MUHAMMAD NAUMAN AFTAB, RABIA AJMAL AND IKRAM-UL-HAQ

Abstract: The poly-β-hydroxybutyrate (PHB) is a thermostable and biocompatible polyester produced by several bacteria under unbalanced nutritional conditions. Among Gram-positive bacteria, which are not well exploited for PHB production on industrial scale, Bacillus appears to be a prospective candidate due to its excellent biopolymer yield and less rigorous fermentation conditions. Batch culture fermentation was carried out for PHB production. The Bacillus cereus NRRL-B-3711 was the most efficient producer of PHB out of five Bacillus species. The optimized production was achieved with 2% glucose, 37°C, pH value of 8 and ammonium sulfate (2.5 g/L) as a nitrogen source. Carbon to nitrogen ratio of 10 significantly affects the PHB accumulation. The selected specie was able to accumulate PHB up to 56% (14.2 }0.07 g/L) on dry cell weight basis after optimization. This corresponds to a 1.87 folds increase in the production. The optical microscopy showed extremely flat surface of bioplastic thin film indicating the brittle failure of PHB under tensile loading. The FTIR analysis revealed C=O and –CH groups, with thermal properties e.g. Tg; 2°C, Tc; 54°C, Tm;162°C and % crystallinity of 51.3 by differential scanning calorimeter (DSC), thus confirming the presence of PHB bioplastic and enhancing its industrial applications.The results surpassed those reported in the literature for PHB production.

Key words: Poly β-hydroxybutyrate, Thermostable, Biocompatible, Fourier transform infrared (FTIR) spectroscope, Differential scanning calorimeter (DSC).