PJB-2016-45
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.
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