Production and Characterization of Polyhydroxybutyrate from Molasses and Corn Steep Liquor produced by Bacillus megaterium ATCC 6748

Abstract

The accumulation of polyhydroxybutyrate (PHB) granule in cells of Bacillus megaterium ATCC 6748 was significantly depended on the ratio of C-source and N-source in the medium culture. Sugarcane molasses (MOL) and corn steep liquor (CSL) were used as renewable raw materials, since they were rich in carbon and nitrogen respectively, leading to develop a low cost process of PHB production. The highest PHB production was observed after 45h of growth (43% w/w, dry matter) when 4% molasses and 4% CSL were used, whereas the highest biomass (7.2 g l-1) was obtained at 4% molasses and 6% CSL. This indicated that bacterial growth increased as CSL concentration increased, whereas the PHB accumulation decreased. The formation rate of PHB up to 0.016 h-1 and specific growth rate up to 0.25 h-1 were observed during growth. The chemical structure and thermal properties of PHB produced from molasses and CSL were obtained the same properties as commercial PHB, except for the higher molecular mass (approx. 3.9 x 106 Da) and the lower degree of crystallinity (60% XC). Thus, the present data indicate that molasses and CSL could be alternatively used for PHB production by this bacterium with high PHB content and adequate properties of biopolymer from a low cost process.