BIODEGRADATION OF DIESEL AND HEATING OIL BY ACINETOBACTER-CALCOACETICUS MM5 - ITS POSSIBLE APPLICATIONS ON BIOREMEDIATION

Twenty aerobic bacterial strains were isolated from altered heating oi l. Among them the strain catalogued as MM5 and identified as Acinetoba cter calcoaceticus is able to grow on hydrocarbon substrates. When sti ain MM5 was grown on heating oil, crude oil and tetradecane, increase s of protein concentration and of caprilate-lipase and acetate-esteras e enzymatic activities were observed in the culture filtrate, with a s imultaneous pH drop. A strong emulsification of petroleum by-products was also noticed. Degradation of heating oil was followed by gas chrom atography and infrared spectroscopy. Presence of available nitrogen an d phosphorus sources were essential for hydrocarbon biodegradation, In tracellular electron transparent inclusions were observed by transmiss ion electron microscopy when strain MM5 cells were grown on hydrocarbo ns. Light and scanning electron microscopy showed bacteria interconnec ted by an extracellular polymer and attached to hydrocarbon droplets a nd to sheets of polymeric material. A bioemulsifier was extracted from the cell-free culture supernatants of strain MM5 grown on tetradecane . The emulsifier is a high molecular weight product that comprises pro teins, sugars and fatty acids and which is resistant to high temperatu re. Strain MM5 should be helpful for the design of strategies for the bioremediation of hydrocarbon contaminated sites.