Isolation, Identification And Degradation Characteristics Of Naphthalene, Phenanthrene-degrading Bacteria From Contaminated Soil

PAHs is one of the Persistent Organic Pollutants （POPs） and has potentialcarcinogenic effects on human. PAHs in the soil environment can be accumulated incrops and vegetables, which will threat human health through the food chain. In orderto find a more cost-effective way to remove PAHs from contaminated soil, singlestrains were separated from PAHs contaminated soil, that took naphthalene orphenanthrene as growth substrate. The strains and their properties were identified. Theremoval of naphthalene or phenanthrene by North China loam were studied. Specificconclusions were as follows:（1） The optimal initial pH is7for the removal of naphthalene by North Chinaloam, which used for domestication of naphthalene-degrading bacteria. The decreaseof initial concentration of naphthalene and the increase of temperature promoted theremoval rate. Bacteriostatic contrast experiment suggested that naphthalene-degradingstrain exists in North China loam. The removal of naphthalene by North China loamfollowed second-order kinetics under different pH, initial naphthalene concentrationsand temperatures conditions.（2） The optimal initial pH is7for the removal of phenanthrene by North Chinaloam, which used for domestication of phenanthrene-degrading bacteria. The decreaseof initial concentration of phenanthrene and the increase of temperature promoted t heremoval rate. Bacteriostatic contrast experiment suggested thatphenanthrene-degrading strain exists in North China loam. The removal ofphenanthrene by North China loam followed second-order kinetics under acid orneutral conditions, initial phenanthrene concentration less than0.7mg/L and thereaction temperature ranging from15to20℃.（3） Fourteen naphthalene-degrading strains and eleven phenanthrene-degradingstrains were screened from North China loam, loess and Chengtu loam. Moreover, thestrains HBN-Ⅱ, HBN-Ⅳ, HBF-Ⅰ and HBF-Ⅳ screened from North China loamwere gram-positive bacteriums, and strains HBN-Ⅰ, HBN-Ⅲ, HBN-Ⅴ, HBF-Ⅱ andHBF-Ⅲwere gram-negative bacterias. The results of16S rDNA PCR-RFLP showed that the strains HBN-Ⅰ, HBN-Ⅱ, HBN-Ⅲ, HBN-Ⅳ, HBN-Ⅴ, HBF-Ⅰ, HBF-Ⅲ andHBF-Ⅳ were classified as Sphingobacterium, Rhodococcus, Pseudomonas,Mycobacterium, Massilia, Arthrobacter, Pseudorhodoferax and Nocardioidesrespectively.（4） Five naphthalene-degrading strains screened from North China loam: Thestrain HBN-Ⅱ was dominant strain and presented the best degradation activity,followed by HBN-Ⅴ, HBN-Ⅰ, HBN-Ⅳ, HBN-Ⅲ. For strain HBN-Ⅱ degradation ofnaphthalene, the greater the initial concentration of naphthalene was, the lower theremoval rate was; the more the biomass was, the faster the removal rate was; theoptimal pH and temperature were8and30℃, respectively. Compared to the effect ofpH, temperature has more effect on the removal rate. The degradation kineticsconformed well to first-order kinetics. The degradation activation energy ofnaphthalene was51.32kJ/mol. The degradation kinetics of naphthalene for strainHBN-Ⅱ fitted well with Monod kinetics. The maximum specific utilization rate andhalf saturation constant were0.0348min^-1, and7.1166mg/L, respectively.（5） Four phenanthrene-degrading strains screened from North China loam: Thestrain HBF-Ⅳ was dominant strain and presented the best degradation activity,followed by HBF-Ⅱ, HBF-Ⅰ, HBF-Ⅲ. For strain HBF-Ⅳ degradation ofphenanthrene, the greater the initial concentration of phenanthrene was, the lower theremoval rate was; the more the biomass was, the faster the removal rate was; theoptimal pH and temperature were7and30℃, respectively. Compared to the effect ofpH, temperature has more effect on the removal rate. The degradation kineticsconformed well to first-order kinetics. The degradation activation energy ofphenanthrene was108.55kJ/mol. The degradation kinetics of phenanthrene for strainHBF-Ⅳ fitted well with Monod kinetics. The maximum specific utilization rate andhalf saturation constant were0.0025min^-1and0.5027mg/L, respectively.