Identification and Characterization of Polyhydroxybutyrate producing Bacillus cereus and Bacillus mycoides strains

Polyhydroxybutyrate producing bacteria from garden soil were isolated and characterized for their morphological, biochemical properties. Based on their 16S rRNA gene sequences, they were identified as Bacillus mycoides DFC1, Bacillus cereus DC1, Bacillus cereus DC2, Bacillus cereus DC3 and Bacillus cereus DC4. The bacteria were screened for PHB production and compared for the intensity of fluorescence using Nile Blue A sulphate and Nile red staining methods. The morphology and the extent of PHB accumulation was also studied using Field Emission Scanning Electron Microscopy (FE-SEM). The PHB production was found to be growth associated. The polymer production by the strains was found to vary from 12.18% to 57.2 % content (w/w) of the dry cell weight. The highest PHB yield was observed in Bacillus mycoides DFC1 accumulating as high as 1.83g/L, amounting to 57.20% (w/w) of cell dry weight. The growth of the bacterium and PHB production using several complex carbon source comprising wheat starch, corn starch, potato starch containing media were also studied. The Bacillus mycoides DFC1 resulted in a high PHB yield of 1.28g/L in wheat starch containing medium at the end of 48h of growth. The polymer produced was extracted and analyzed for its purity using Fourier Transform Infrared spectroscopy (FTIR) and was confirmed to be PHB.