Polyhydroxybutyrate and Hydroxyvalerate Production by Bacillus megaterium Strain A1 Isolated from Hydrocarbon-Contaminated Soil

Abstract

In this study, we attempted to find an alternative microbial resource as a bioplastic producer. Among all of the isolates, the A1 strain produced 44% poly(-hydroxybutyrate) (PHB) in proportion to its dry cell weight. The molecular identification of the 16S RNA gene showed that this bacterium was a strain of Bacillus megaterium with the accession number KC579390. The optimization studies led us to the conclusion that the highest poly(-hydroxybutyrate-co-hydroxyvalerate) (PHBV) production was 78% when 5% molasses was used as the carbon source at pH 6 and 35 degrees C after 60 h of incubation. Attenuated total reflectance Fourier transform infrared (FTIR) spectroscopy and H-NMR were used for chemical characterization. Differential scanning calorimetry was used to determine the thermal properties of the PHB and PHBV that were synthesized with sucrose and molasses as carbon sources, respectively. The FTIR spectra of the polymers were characterized by typical absorption bands at 1715-1720 cm(-1) for amide-bound CO bands and 1261-1279 cm(-1) for an ester-bound CO band. The molecular weights of PHB and PHBV synthesized with sucrose and molasses were calculated as 428 and 498 kDa, respectively, according to the viscometric method. This study indicated that the B. megaterium strain A1 is an alternative microbial resource as a bioplastic producer