Study On Screening Combination Of Oil Degrading Bacteria And Simulated Remediation Of Oil Contaminated Soil

Oil-induced environmental pollution poses a significant threat to human health.Although physical and chemical methods have been developed for remediating oil pollution,they have certain limitations,such as high cost and the potential for secondary contamination.Microbial remediation,on the other hand,offers economic,green,and eco-friendly advantages and has garnered significant attention.However,foreign microorganisms often struggle to adapt to complex environments during practical field remediation,which can result in decreased degradation efficiency and poor remediation effects.Therefore,developing highly adaptable microbial remediation technology that produces stable remediation results is crucial for addressing environmental issues caused by oil pollution.In this study,16S amplicon sequencing technology was utilized to analyze the microbial community structure during the enrichment process to screen for oil-degrading bacteria.A combination of oil-degrading strains was then constructed for simulated remediation studies.Microbial diversity,oil content,nitrogen,and enzyme activity changes during the remediation process were assessed as a means of evaluating the effectiveness of the combination.The primary research findings are as follows:1.After enrichment culture of oil-contaminated soil microorganisms,at the level of phylum classification,the changes of bacterial community mainly occurred in Actinobacteria and Proteobacteria.Pseudomonas was the dominant genus in the early stage of enrichment,and Dietzia was the dominant genus in the later stage of enrichment.A total of 57 microorganisms were isolated from the enrichment system,of which 3 were potential new species.Two oil-degrading bacteria,Rhodococcus qingshengii OS62-1 and Dietzia maris OS33,were screened.The oil degradation efficiency of the two strains was72.28±3.60%and 65.46±3.57%,respectively.2.Under the guidance of the variation of bacterial community during the enrichment culture of oil-contaminated soil,an oil-degrading combination composed of oil-degrading bacteria R.qingshengii OS62-1 and assistant bacteria Pseudomonas songnenensis P35 at a ratio of 1:1（v/v）was constructed.Under the condition of initial oil concentration of 5000 mg·L^-1,the oil degradation efficiency of this combination for 7days was 85.72±3.21%,the oil degradation half-life was 2.20 day,and the degradation rate constant was 0.35 day^-1.In addition to the significant improvement of oil degradation efficiency（p<0.05）,the combination had more advantages for the degradation of C₁₀-C₁₇components in oil,with a degradation rate of 94.61%.The content of alkanes,aromatic hydrocarbons and wax in oil components was also significantly lower than that of single strains（p<0.05）.The oil degradation efficiency of this combination was significantly higher than that of a single strain in the range of p H 5-10 and Na Cl concentration of 0-60 mg·L^-1（p<0.05）.3.A 25-day simulated remediation study was carried out.Under the condition of initial oil concentration of 5000 mg·kg^-1,the oil content in the sample decreased to1973.00±169.30 mg·kg^-1after 25 days of remediation,and the total nitrogen（TN）in the soil decreased from 616.70±54.49 mg·kg^-1on day 0 to 158.70±15.17 mg·kg^-1on day25.The content of nitrate nitrogen（NO₃^--N）decreased from 537.10±31.70 mg·kg^-1on day 0 to 115.81±15.71 mg·kg^-1on day 25,and the content of nitrite nitrogen（NO₂^--N）increased from 6.30±1.10 mg·kg^-1on day 0 to 58.10±6.60 mg·kg^-1.The activities of catalase（S-CAT）,dehydrogenase（S-DHA）,lipase（S-LPS）and polyphenol oxidase（S-PPO）in the samples showed an upward trend.Compared with the control group（PSC）,the enzyme activity of the microbial treatment group（MT）was significantly increased（p<0.05）.Oil was positively correlated with TN and NO₃^--N content,and negatively correlated with NO₂^--N,S-CAT,S-DHA,S-LPS and S-PPO.The importance of each environmental factor to oil content was as follows:NO₂^--N（19.25%）>S-LPS（17.33%）>TN（17.07%）>NO₃^--N（15.62%）>S-CAT（15.19%）>S-PPO（10.04%）>S-DHA（8.20%）.4.The combination treatment（MT）increased the complexity and stability of the molecular ecological networks（MENs）in the soil during the indoor simulated remediation process.Oil was significantly negatively correlated with Nocardioides,unclassified＿Intrasporangiaceae,unclassified＿Nocardioidaceae,Rhodococcus,unclassified＿Micrococcaceae and Pseudomonas（p<0.05）.It was significantly positively correlated with Sphingomonas,Lysobacter,unclassified＿Gemmatimonadaceae and Dongia（p<0.05）.