Characterization of Polyhydroxyalkaonoate Extracted from Bacillus megaterium JHA and Its Biodegradation Studies

Polyhydroxyalkanoates (PHAs) are naturally occurring polymers that are synthesized by several bacterial species as an energy reserve material. They can be used as a sustainable alternative to petroleum derived plastics. A gram positive bacterium, Bacillus megaterium JHA isolated from oil contaminated soil showed the potential ability to accumulate high concentration of PHA using glucose as a substrate. In the current study, the biopolymer was extracted from the above strain using a solvent (chloroform) extraction method to obtain a thin film of PHA. This film was characterized using analytical techniques like confocal microscopy, high performance thin layer chromatography, fourier transform infrared spectroscopy, nuclear magnetic resonance and gel permeation chromatography. These techniques showed similarity between the functional and chemical groups of PHA and the standard molecule i.e. Polyhydroxybutryrate (PHB), indicating that it is a derivative of PHB. The thermal properties of the biopolymer were also determined using differential scanning calorimeter and thermo-gravimetric analysis. The weight- average molecular weight and number- average molecular mass of the biopolymer was detected to be 43.47kDa and 25.53kDa, respectively, with a polydispersity index of 1.7. It further showed the melting temperature of 163.19°C, whereas the thermal decomposition temperature was found to be 285.68°C. The IC50 value of the biopolymer was calculated as 0.311mg/mL, by MTT assay, which indicates its suitability for various biomedical applications. Further studies on biodegradable nature of the biopolymer were carried out using scanning electron microscopy. Apart from above mentioned analytical characteristics, the unique feature of the polymer was its ability to degrade completely in compost soil under facultative conditions within a period of 60-90 days.