Production and characterization of PHB-HV copolymer by Bacillus thuringiensis isolated from Eisenia foetida

Polyhydroxyalkanoates (PHAs) are one of the most important biopolyesters produced by vast number of microorganisms that exist in the environment. PHAs gained much attention due to its inherent biodegradable and biocompatible ability along with its physicochemical properties, which are similar to those of conventional petroleum-based plastics. In the present study, PHA producing bacterial strains was isolated from earthworm. Initially, four bacterial strains were selected based on the intensity of fluorescence from 80 non-clonal isolates. Bacillus thuringiensis (B.t.) E101 was identified as the bacterium producing highest yield of PHA (3.6 ± 0.04 g L^-1 ) through biochemical and molecular techniques such as 16S rRNA gene sequence analysis. Growth parameters such as carbon, nitrogen sources, and incubation time were optimized with respect to higher PHA production. Both qualitative (Fourier transform infrared spectroscopy and nuclear magnetic resonance) and quantitative (GC-MS) characterizations revealed that the polymer produced by B.t.E101 contains the characteristic peaks for poly(3-hydroxybutyrate-co-3-hydroxyvalerate) copolymer. This is the first report for the occurrence, successful isolation, and characterization of PHA producing Bacillus sp. from earthworm.