Exploring the Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Production Potential of Total Petroleum Hydrocarbon Degrading Bacteria Using Oily Sludge Waste as Feedstock

Abstract

Though bioremediation of hazardous petroleum refinery waste (oily sludge) has been practiced for the last few decades, the present study proposes to obtain polyhydroxyalkanoate (PHA)-based bioplastic polymer from it as a valuable byproduct parallel to its treatment. In the present study, nine fast-growing and sodium benzoate degrading bacterial strains belonging to the genera Achromobacter, Pseudomonas, Acinetobacter, Ochrobactrum, and Pannonibacter were found to be PHA-positive. The screened bacterial cultures showed total petroleum hydrocarbon (TPH) degradation in the range of 31% to 91% from 1% oily sludge containing medium and could accumulate PHA in the range of 50% to 92%. The Fourier Transform Infrared (FTIR) interferogram of extracted PHA represented PHA-related functional groups, while proton nuclear magnetic resonance (^HNMR) spectra showed chemical shifts corresponding to a −CH₃ of 3HB (0.88 ppm) and 3HV (1.5 ppm) monomers, thus confirming it as poly(3-hydroxybutyrate-co-3-hydroxyvalerate) or P(3HB-co-3HV). The thermal features of extracted P(3HB-co-3HV) such as low melting temperature (T_m) and low % crystallinity (%Xc) are industrially more significant. Ochrobactrum ciceri strain AWIS01 was found to be the most efficient organism, showing 0.720 g/L P(3HB-co-3HV) production while degrading 90.06% TPH when 1% oily sludge was provided as the sole source of carbon. In the future, such bacteria can be used to produce bioplastic polymer from oily sludge.