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ABSTRACT-Mechanical workshops release huge levels of used engine oil into the surroundings. Many mechanical workshops do not have proper disposal mechanisms and eventually used engine oil reaches the surrounding soil. The hydrocarbons present in used engine oil damage the environment and human health. There are microbes in nature which have the ability to degrade the used engine oil. Such microbes can be isolated and used for the biodegradation of hazardous and recalcitrant hydrocarbons occurring in used engine oil. The present study deals with the four used engine oil degrading bacterial species isolated from oil contaminated sites of mechanical workshops. The bacterial species were Bacillus, Acinetobacter, Pseudomonas and Micrococcus. The optimum pH and temperature on the oil degradation activity of bacterial species were determined. In addition, effect of various amino acids on the oil degradation ability of these bacterial species was studied and best amino acid for oil degrading activity was determined. All the four bacterial species exhibited highest oil degrading activity at pH 7.0. The optimal temperature required for maximum oil degradation activity by Bacillus and Acinetobacter species was 33 0 C and 35 0 C respectively. At 31 0 C Pseudomonas and Micrococcus species had shown maximum oil degradation activity. All the bacterial species had shown enhanced oil degradation activity in methionine supplemented medium. Bacillus species was found to be efficient among all the four species.

Polyaromatic hydrocarbons (PAHs) entering into the environment from various sources are highly toxic and deleterious to living beings. Naphthalene is one the sixteen toxic PAHs enlisted by EPA, US. Physical and chemical methods used for the removal of PAHs from polluted sites are not effective. Bioremediation which employs microbes to metabolize PAHs is an alternative method to physical and chemical processes. Naphthalene is considered as model compound for the biodegradation studies of PAHs. In the present study the effect of seven selected metal ions on naphthalene degrading ability of three bacterial species (viz., Bacillus, Pseudomonas and Micrococcus) isolated from oil contaminated soils of mechanical was studied. Five metal ions were reported to enhance the naphthalene degrading activity and two found to decrease the activity. These bacteria can be further improved and used for bioremediation of polluted sites.

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