Biodegradation of Waste Cooking Oils by Klebsiella quasivariicola IUMR-B53 and Characteristics of Its Oil-Degrading Enzyme

Abstract

Cooking oil is one of the largest pollutants in the environment and much of it comes from kitchen waste around the world. This study aimed to isolate effective oil-degrading bacteria for disposing food waste and determine the functional enzyme. Oil-degrading bacteria were isolated from kitchen waste for efficient degradation of edible oils in kitchen waste. Its growth and oil degradation characteristics were investigated in basic salt medium with edible oils as the sole carbon and energy source; the lipase gene was cloned and expressed in Escherichia coli. A novel oil-degrading bacterium was isolated identified as Klebsiella quasivariicola IUMR-B53 (CGMCC No. 18024). It degraded 95.76% oil at 37 °C after 144 h incubation in mineral salt medium with soybean oil as the sole carbon source. The maximum degradation rate was observed at 37 °C with 0.3% NaCl, and the most suitable nitrogen source was 0.1% ammonium sulfate at pH 7.0. Additionally, a novel lipase gene was cloned from the strain, which was 95.43% similar to that of Klebsiella aerogenes (NCTC10006). Results of sodium dodecyl sulfate–polyacrylamide gel electrophoresis showed that the molecular weight of lipase was approximately 35 kDa, and its activity was 3.29 U/mL at 37 °C, which was 66.50% greater than the control group. The study demonstrated that K. quasivariicola IUMR-B53 is an effective oil degradation strain and could use oil as a source of carbon and energy for growth. In addition, these findings provide a theoretical and practical basis for treating oil contamination.