Oil degrading organisms were enriched in MSM medium supplemented with used engine oil. Organisms showed zone of clearance of 7-24 mm on TBA and 3-16 mm on used engine oil supplemented MSM plate. The % degradation of used engine oil was 14 to 37%. Isolate DP-1 showed highest activity, it was identified as Pseudomonas aeruginosa DP-1 by 16S r-RNA gene sequencing analysis. | Degradation of discarded used engine oil by Pseudomonas aeruginosa DP-1 and its optimization