Aerobic Biodegradation of Gasoline Compounds by Bacteria Isolated from a Hydrocarbon-Contaminated Soil

This article reports the isolation and characterization of two strains of bacteria from a hydrocarbon-contaminated industrial area (CubatAo-Brazil), which were able to degrade gasoline compounds, such as benzene, toluene, and ethylbenzene (BTE), the highest water-soluble fractions of commercial gasoline. Among the isolates, 16S rRNA gene sequence analysis revealed that these two strains belong to the gamma group of proteobacteria, with 95.0% and 99.0% similarity to the 16S rRNA gene sequences of Serratia sp. (HCS1) and Pseudomonas sp. (HCS2), respectively (BLAST, GenBank, NCBI). Degrading potential of each isolate was measured by inoculating pure culture in a mineral medium containing BTE or commercial gasoline (containing ethanol 24% [v/v]) as the only carbon source and monitoring hydrocarbon disappearance rate at regular time intervals. Growth of isolates in mineral medium containing hydrocarbons was monitored by measuring the turbidity (OD 600nm) and substrate consumption by high-performance liquid chromatography (in the BTE assays) and gas chromatography-mass spectrometry (gasoline biodegradation assays). After 15 days, BTE (50mg/L) were totally degraded by both strains. After 21 days, HCS1 and HCS2 had also degraded commercial gasoline by 60% (v/v) and 80% (v/v), respectively. Results suggest that these strains have a high level of tolerance to hydrocarbon toxicity and, consequently, have potential applications in the biotreatment of industrial wastewaters or in situ bioremediation of hydrocarbon-contaminated soils.