Purification and characterization of polyhydroxybutyrate produced from thermophilic Geobacillus sp. AY 946034 strain

Abstract

Thermophilic Geobacillus sp. AY 946034 strain was found to accumulate poly-3-hydroxybutyrate (PHB). The highest PHB percent yield was found under phosphorous limiting conditions (68.9% of cell dry weight), using glucose as the sole carbon source. Higher values of enzyme (ketothiolase, CoA reductase and PHA synthetase) activities of thermophilic strain indicated that bacteria use the classical pathway of PHB biosynthesis when are cultured on glucose as the sole carbon source.
The characterization of biopolymer was carried out using FT-IR, DSC and capillary viscosity methods. The FT-IR analysis of the purified polymer revealed similarities in the spectra of the microbial and standard PHB at 2 983, 2 935, 1 722, 1 456, 1 278 and 1 053 cm–1 wave numbers. The thermal analysis showed the accumulated PHB to be semi-crystalline polymer (42%), having a thermal degradation temperature of 280 °C, melting temperature of 168.8 °C and apparent melting enthalpy of 62.98 Jg–1 . Molecular weight of the polymer was found to be 556 kDa.