Effects of Indigenous Microbial Consortium in Crude Oil Degradation: A Microcosm Experiment

Microbial biodegradation is a bio-treatment method for attenuating crude oil contaminated soils. The purpose of present study was to select and recognize indigenous bacteria and to investigate the capability of the bacterial consortium to remove crude oil in a planned microcosm. Capability of the bacterial growth in agar plates containing crude oil was used to select the isolated crude oil eating bacteria. Soil samples were collected from different contaminated sites nearby the exploitation unit of Karoon-3, Ahvaz, Iran, and incubated by individual and mixed bacterial consortium at 30°C for a 90 day period time. Two indigenous isolates were selected and designated as S10 and S31. According to 16S rRNA sequencing, S10 was identified as a new strain of Bacillus subtilis and S31 as Bacillus licheniformis. The results showed that the highest cell mass was in 10th day of incubation time with about 1.7×107 CFU/g, for bacterial consortium. The highest total petroleum hydrocarbons degradation (C%) in the first 10 days of incubation time raised up to about 77.5% for bacterial consortium, and also residual C:N ratio deleted about 73%. Results emphasized that the planned microcosm in laboratory with controlled conditions using consortia of the selected indigenous bacteria can make the crude oil biodegradation close to the optimal conditions and have a good potential for application in bioremediation of crude oil contaminated soils, as compared to the individual strains. This is the first report on planned microcosm and microbial consortium of Karoon soil contaminated with crude oil.