Isolation Of Petroleum-degrading Strains And Their Bioremediation Effects On Petroleum-contaminated Soil

Many studies on bioremediation of oil-contaminated soil were reported at currentTime. However, Bioremediation is considered as the most promising techquine towardspetroleum-contaminated soils which has advantages of low cost, perfect maintenanceand minor secondary pollution to the environment. Many factors can influencebioremediation effects which include soil moisture, pH, oxygen, C/N/P ratio, and thenumber of degrading strains. But few literature have described the key factor whichaffected the total petroleum hydrocarbon biodegradation. On the other hand, exogenousstrains may lose or decrease the biodegradation ability because changes of outsidefactors and competition with indigenous strains. All these factors restricted practicalapplications in site remediation.In this study, two petroleum degrading strains which can produce biosurfactantswere isolated from petroleum-contaminated soil by culturing in beef extractpeptone-bush hass medium and rescreening by using blue gel medium. The differenttreatments towards petroleum-polluted soils which include bioaugmentation(add twodegrading strains to soils), biostimulation (add N and P to soils), bioaugmentation andbiostimulation (add degrading strains supplement with N and P), natural attenuationwere studied. The components of TPH in petroleum-polluted soils were analyzed byGC-FID. The number of TPH-degrading strains were determined by MPN. Underdifferent processing conditions, the change of degrading genes, total petroleumhydrocarbons degradation rate, degrading genes relationships, the impact of variousfactors on degrading genes in petroluem-polluted soil were studied.Results indicated that:(1) two bacteria showed high biodegradation rates towards TPH in moderate oil-contaminated soil and the biodegradation rate of TPH in70dayswas52%. The optimum condition of remediation petroleum-polluted soil as follows:adding two strains to the petroleum-polluted soil supplemented with N and P, and keptsoil moisture40%. Under this condition, the degradation rates of TPH and n-alkaneswere respectively75%and66%. The results of GC-FID show that the less than C22canbe better metabolized by microorganisms.（2）The study also demonstrated that addingstrains and nutrients (N and P) to petroleum-polluted soil were key factors for TPHbiodegradation compared with soil water capacity and indigenous strains forbioremediation petroleum-polluted soil.（3） Soil water content, the number ofdegradation genes, and TPH biodegradaion rates showed positive relations. thedegradation genes of n-alkane and polycyclic aromatic hydrocarbon biodegradationincreased when added degradation strains, or supplemented nutrients N and P to theoil-polluted soil.（4）The number of degradation strains increased when addeddegradation strains and supplemented nutrients N and P to the oil-polluted soil.