Petroleum Biodegrading Property of Microbial Consortia from a Contaminated Site

Abstract

Hydrocarbons enter into the environment mainly via waste disposal, accidental spillage and leakage tankers. Hydrocarbon toxicity is caused by low-boiling-point aromatic hydrocarbons including benzene, toluene, xylene, naphthalene etc., and the toxicity is spread in almost all compartments of the environment, e.g. plants by damaging protoplast, animals by causing various lung diseases and cancers and atmosphere by decomposing the ozone layer, and it can be prevented also by using hydrocarbon-degrading microorganisms. In this investigation, at first six hydrocarbon-degrading bacterial strains were isolated from oil-contaminated soil near a petrol pump of petrochemical industries at Budge Budge, Kolkata. Their hydrocarbon-degrading ability was checked by their ability to grow in mineral salt-based Bushnell Haas medium supplemented with petrol as a sole carbon source. Along with gram characterization and different biochemical tests, their hydrocarbon tolerance level was measured, which was found to be up to 8% for isolates 1, 3 and 4. The isolates were also examined for the activity of three different hydrocarbon-degrading enzymes, namely, laccase, tyrosinase and catechol oxidase. It was found that isolate 3 had the highest activity for these enzymes and it could also degrade the petroleum to produce CO₂ within 7 days. The isolate also had metal-adhering ability by forming biofilm on it. From the colony morphology and microscopic analysis, it was presumed that isolate 3 was an actinobacteria, which was finally proved by their ability to grow in selective medium – starch casein agar – and 16S rDNA sequencing, and it was found that isolate 3 was Streptomyces bacillaris S4BW2. So these isolates seemed to have potential for bioremediation of hydrocarbon pollution and, thus, can serve as a potential tool to degrade petroleum waste.