Biodegradation of Gachsaran crude oil under extreme environmental conditions by an efficient microbial consortium

The biodegradation of Gachsaran crude oil under extreme environmental conditions has been investigated based on the development of a fermentative process with a new consortium of Enterobacter sakazakii and Pseudomonas sp. (ERCPPI-3) which was isolated from heavy crudeoil-contaminated soil in the south of Iran. The effects of crude oil concentration, temperature, pH, salinity and type of surfactant on the growth rate of ERCPPI- 3 in the presence of Gachsaran crude oil as the sole source of carbon were studied. The obtained results revealed that the consortium was able to grow at crude oil concentrations up to 11.3% (w/v), temperatures up to 73°C, salinities up to 15.4%, and in the pH range 4 to 10. However, as the concentration of crude oil was increased from 0.25% to 11.3%, the percentage of crude oil degradation decreased from 84.5% to 17.6%. Temperature of 40°C and pH of 7.0 were found to be the optimum conditions for maximum biodegradation rate. The experiments also showed that the isolated consortium produces a biosurfactant mixture using Gachsaran crude oil as the sole source of carbon with excessiveoil spreading and emulsification properties. The produced biosurfactant by ERCPPI-3 improved the degradation rate of Gachsaran crude oil and the used chemical surfactant had an inhibitory effect. The experiments performed in under in situ conditions demonstrated that biodegradation of hydrocarbons were at a reasonable rate. These results suggest that consortium ERCPPI-3 has the ability to degrade crude oil under ex situ and in situ conditions. Besides, a mathematical model has been presented to predict the extent of biodegradation of Gachsaran crude oil under various environmental conditions. The results obtained by the proposed model have been compared with the experimental data and a good agreement was obtained between the results