Study of microbial combination and nutrients in remediation of petroleum-contaminated soil

In this study, degradation of polluted soil (with 1, 4 and 9% petroleum contamination) was performed using different microbial combinations and nutrients. Biosurfactant production and lipase production of the isolated microbes were also tested. A5 and A14 (isolated from petroleum-contaminated soil (PCS)) and G1 and G6 (isolated from garden soil) showed a positive result in the biosurfactant production test. A1, A5, A6, A13, A14, A15, A16, G1 and G5 showed zones around agar wells; these bacterial strains produced lipase. Combinations of microbes were applied in treatment of 1% PCS; the combination of only bacteria and the combination of bacteria and fungi showed petroleum degradation of 71 and 73·17%, respectively. In 4 and 9% PCS, the degradation activities of microbes decreased; the microbes needed a longer time to activate the large amount of petroleum. Furthermore, tests with and without nutrients were conducted to determine the effect of using nutrients in bioremediation of PCS. The results showed that petroleum degradation percentages from the treatment using nutrients were about 5% higher than the degradation percentages from treatments without nutrients.