Production of Polyhydroxyalkanoate by Bacillus thuringiensis Isolated from Agricultural Soils of Cascas-Peru

Abstract Polyhydroxyalkanoates (PHA) are biodegradable biopolymers of microbial origin that can be alternative materials to decrease the extensive use of plastics of petrochemical or synthetic origin. Thus, the selection of microorganisms with potential for PHA production from unexplored natural sources is a strategy to find bacterial species of high value. In the current study, 55 microbial strains related to bacteria were isolated from agricultural soils from Cascas, Peru. Initially, 4 strains were selected by Sudan Black B staining and Nile blue A fluorescence methods, subsequently, they were screened to examine its production capacity of PHA. Bacillus thuringiensis SP7-1 strain was selected based on its high production of PHA at 0.54 ± 0.16 g/L with an accumulation of 19 % by weight of cell biomass, during 72 h at 30 ºC. The isolate was characterized by its morphology, biochemical and molecular tests through the 16S rRNA gene. The extracted PHA was characterized quantitatively by HPLC and qualitatively by FT-IR. Its thermal properties were determined by TGA and DSC, revealing a thermal degradation temperature of up to 270-303 ºC and a melting temperature of 166.88 °C. Therefore, Bacillus thuringiensis SP7-1 can be used as a model system for the production of PHA with efficient thermal stability, and optimize its performance in future research, as well as being applied in obtaining of molded bioplastics.