Enhanced lipase production and characterization from Aeromonas media VBC8: Applications in biodegradation of lubricating oil waste

This study aimed to explore the potential of a novel indigenous strain for the improved production of lipase from castor oil-contaminated soil. Among the various isolates, Aeromonas media VBC8 was found to be the most effective for lipase production. The effect of different inducer oils (olive, peanut, soybean, rice bran, sunflower, coconut, sesame, and fish liver oil) on the biomass of A. media VBC8 and its lipase activity was determined. Among the various oils assessed, fish liver oil exhibited highest lipase activity, with 89 U/mL with 9.1 g/L of biomass. Furthermore, Box-Behnken Design was used to optimize the cultural conditions resulting in an enhanced lipase activity of 1156 U/mL. The lipase was purified through ammonium salt (60 w/v %) precipitation, desalting and ion exchange column, achieving a yield of 16 % and specific activity of 98.4 U/mL. The purified lipase remained active over a wide range of pH 4.0–11.0 and temperature of 10–80 °C with maximum activity at pH 8.0 and 40 °C. SDS-PAGE analysis revealed the lipase's molecular weight to be 94 kDa. The study also evaluated the role of crude and purified lipase in the biodegradability of lubricating oil waste, achieving a maximum fatty acid conversion of 39 and 76 %, respectively, after 7 h incubation at room temperature.