| Polycyclic aromatic hydrocarbons(PAHs)are a class of highly toxic organic pollutants with carcinogenic,teratogenic,and mutagenic characteristics.The primary reason for its widespread existence in the environment is human activities,such as incomplete combustion of oil,coal,and wood,natural gas,straw,etc.Due to its properties of mutagenicity,weak water solubility and strong stability,PAHs are able to continuously accumulate in the environment and pose a potential threat to human survival and ecological balance through the energy flow of the nutrition chain.In view of the potential threat,the remediation of PAHs pollution is urgent.Microbial remediation mainly uses the degradation strains to transform and metabolize harmful substances to achieve the removal of pollutants.At present,it has become a widely used method for controlling organic pollution.It has become a widely used method of organic pollution control for the characteristics such as simplicity,economy,and no secondary pollution.Screening degraded strains from contaminated systems is a key step in the implementation of microbial remediation.In this study,the Teflon membrane and sponge were used as the adsorption medium to isolate the adsorptive PAH-degrading strains from the soil around the oil wells in northern Shaanxi.Seven strains which are used PAHs as the sole carbon were obtained by using L9 culture medium through enrichment and streak separation.The strains belonged to the genera of Acinetobacter,Pseudomonas putida,Enterobacter cloacae,Ochrobactrum,Sphingobacterium,Enterobacter cloacae,Enterobacter,respectively.The results of Gram’s dye showed that all of these strains were Gram-positive bacteria.The results indicated that different kinds of degrading species can be obtained by using adsorption membrane.The adsorptive degrading strains had higher PAHs degradation ability when compared to the non-adsorptive bacteria which were isolated using classical isolation method.Among them,one strain of Enterobacter MK505391 which were isolated by using Teflon membrane as adsorptive membrane showed the highest PAHs degradation ability in liquid phase medium,and the degradation efficiency of 50 mg/L phenanthrene has reached 73.8% after 21 days of inoculation.This strain also enhanced the PAHs degradation rate in petroleum contaminated soil.Laboratory simulated remediation research on PAH-contaminated soil and petroleum-contaminated soil by degrading bacteria,the results show that inoculation with degrading bacteria for bioaugumentation repair can significantly improve the removal rate of pollutants in the initial stage of the repair,but with the extension of the repair time,the removal rate of pollutants becomes slower.The removal rate of PAHs in the contaminated soil at the end of the remediation was compared with that of the unintensified inoculated treatment,and the intensive repair of the inoculated strain can significantly improve the PAHs removal rate in the contaminated soil.However,changes in the inoculation amount of strains will affect the removal effect of TPH in petroleum contaminated soil.High-throughput sequencing was used to analyze the effects of changes in soil flora on PAHs degradation.Studies have shown that the decrease in the abundance of Acidobacteria and the increase in the abundance of Chloroflexi,Firmicutes,and Bacteroidetes may promote the degradation of PAHs in the soil.At the genus level,the existence of Sphingomonas is related to the degradation of polycyclic aromatic hydrocarbons,but its excessive abundance will affect the growth of other strains,thereby inhibiting the degradation of pollutants by microorganisms. |
PDF Full Text Request