Exploration of polyhydroxyalkanoate-producing bacteria in diverse soils with emphasis on bioremediation

Polyhydroxyalkanoates (PHAs) are biodegradable polymers with immense potential as eco-friendly alternatives to conventional plastics. The study aimed to screen for PHA-producing bacteria in different soil samples and evaluating for their hydrocarbon utilization. In the present study, a total of 30 soil samples were collected from different sites, such as petrol bunk, sewage, and garden. Among the total bacterial isolates obtained, 30 showed positive PHA production by preliminary screening Sudan Black B, Nile blue, and Nile red staining techniques. Quantitative estimation of PHA was performed using a shake flask experiment in a minimal medium with an initial pH of 7, 10% (v/v) inoculum, 30°C, 170 rpm at 72 h. The isolate Bacillus subtilis PHAD13 produced the highest PHA 59% extracted by sodium hypochlorite method. Polymers from Bacillus amyloliquefaciens (PHAD7), Bacillus subtilis (PHAD13), Bacillus cereus (NS1), and Klebsiella sp. (NG5) were characterized by FT-IR analysis. GC-MS analysis revealed the presence of PHA copolymer, with tridecanoic acid (C13:0, MCL-PHA), and longer chain monomers (C15:0-C18:1, LCL-PHA); coexistence indicates heterogeneous monomer integration. The bacterial growth on Bushnell-Haas agar supplemented with spent engine oil demonstrated hydrocarbon tolerance indicating its bioremediation potential. The present study demonstrates the dual functional capability of Bacillus subtilis for bioplastic production and hydrocarbon degradation.