Biodegradation of the Most Heavier Fraction of Crude Oil, Asphaltene, by Bacillus toyonensis BCT-7112

Abstract

There have been few records on microorganisms with the ability to survive and utilizehigh concentrations of heavy fractions of crude oil like asphaltene. These organisms are applicable in different aspects of petroleum industry from extraction to refining and environmental pollution treatment. To isolate such indigenous bacteria, a highly viscouscrude oil was selected and its asphaltene extracted. Isolation, enrichment, and purification of the bacterium were done in ISO 9439 medium at room temperature and 45°C as well. Studying morphological characteristics, biochemical and molecular tests were performed to identify isolated bacteria. The 16S rRNA gene sequence was subjected. To study the biodegradation of asphaltene, isolated bacteria were cultured in ISO 9439 medium for 2, 20 and 50 d at 25°C and 45°C.The efficiency of asphaltene degradationwas evaluated by FT-IR spectroscopy analysis. The bacterial species, which could use asphaltene as the sole carbon and energy source, were selected. Among all, Bacillus toyonensis BCT-7112 had the most degrading ability on asphaltene. The percentage of asphaltene degradation after 50 d of incubation at 25°C was 64.8%, and it was 60% at 45°C. Based on the FT-IR analysis, the isolate had the most biodegrading effect on Aldehyde compounds in comparison with other asphaltene ingredients. This amount of degradation is the most among the present records in literature.