Karmen Plohl, Hermina Leskovšek
Department of Environmental Sciences, Jožef Stefan Institute, Jamova 39, SI-1001 Ljubljana, Slovenia

Mihael Bricelj
National Institute of Biology, Večna pot 111, SI-1000 Ljubljana, Slovenia

The biodegradability of petroleum hydrocarbons from motor oil (Proton Avant, Petrol, Slovenia) was studied in aqueous media using different bacterial strains isolated from native catchments in Štajerska and Prekmurje. An unidentified bacterial strain AL-12 from the culture of cyanobacteria was found as the most successful in degrading alkanes from n-C15 to n-C40 present in the fresh motor oil in a quantity of  98%.  Small aliquots of motor oil were incubated aerobically for a period of up to 50 days, following the hydrocarbon content by GC/MSD analysis. Within 5 days of incubation up to 70% of n-alkanes n-C15-n-C22, up to 45% of n-C22-n-C30 and up to 20% of n-C30-n-C40 were biodegraded. As expected, abiotic losses were smaller with increasing alkane chain length, but increased with incubation time.