Diesel oil and lubricants are hydrocarbons commonly used in the world. Contamination of environment by used
lubricating and diesel oil is rapidly increasing due to global increase in the usage of petroleum products,
particularly in developing countries. This has been shown to have harmful effects on the environment and
human beings. Thus, the present work aims to optimize diesel oil and used oil biodegradation by bacterial strains
isolated in wastewaters. Two strains namely S2 and S7 were incubated alone or together with diesel oil or Total
Quartz 9000 used oil supplemented or not with yeast extract, peptone and trace elements for 14 days. The level
of both petroleum hydrocarbons degradation was determined by gravimetric assay. The results obtained showed
that the presence of strain S2 or S7 increased significantly hydrocarbons degradation. The association of strains
S2 and S7 increased the biodegradation of hydrocarbons over the one of strain S7 alone (p

biodegradation, diesel oil, Total Quartz used oil, nutrient factor