Study On The Degradation Of PAHs In Soil By Extracellular Polymer Of Fusion Strain F14

Polycyclic Aromatic Hydrocarbons(PAHs)are generally found in the environment and are stable,difficult to decompose,potentially teratogenic,carcinogenic and mutagenic organic compounds that pose a great threat to human life and health.Microbial remediation technology has received wide attention from experts and scholars because of its relatively simple operation,good remediation effect,weak impact on the environment and almost no secondary pollution,and has become the main way to remove PAHs.Extracellular polymertic substances(EPS)are polymeric substances secreted by microorganisms in the process of metabolism and attached to the surface of microorganisms and the surrounding environment.The role of EPS in the process of microbial remediation of contaminated soils is receiving more and more attention as the research on microbial remediation technology progresses.In this paper,polycyclic aromatic hydrocarbon efficient degrading bacteria fusion strain F14 was used as the research object,and phenanthrene was the target pollutant.The mechanism of the role of EPS in the remediation of phenanthrene-contaminated soil by fusion strain F14 was investigated to better enrich the bioremediation mechanism of PAHs-contaminated soil and provide scientific basis and theoretical support for future field remediation of PAHs contamination.The main research results are as follows.(1)The effects of different concentrations of phenanthrene induction on the extracellular polymer of the fused strain F14 were characterized in terms of component content,degradation effect and structural changes.The study showed that with the increase of phenanthrene induction concentration,the EPS fraction content and protein peak intensity showed an increasing and then decreasing trend,and reached the maximum value at the phenanthrene concentration of 100 mg/L.The results of FTIR analysis showed that the hydroxyl,amino,amide groups(carbonyl)and carboxyl groups on the EPS surface were all involved in the degradation process.gradually became smaller.(2)The surface tension of EPS and the degradation of phenanthrene were determined by changing the conditions of different factors.The results showed that with the increase of EPS concentration and p H,the surface tension of EPS showed a trend of increasing and then decreasing,and the surface tension reached the lowest value at EPS concentration of 35.72mg/L and p H=7(natural state).Subsequently,the degradation of phenanthrene was carried out,and it was found that the optimum temperature for EPS to degrade phenanthrene was 30 o C,the optimum concentration was 35.72 mg/L,and the optimum p H was 7.It was reasonably inferred from the experiments that the adsorption and degradation process of EPS for phenanthrene,EPS first used hydrophobic interaction with phenanthrene,then used the hydrophilic part to wrap it on the EPS surface,and then used enzymes to degrade phenanthrene.(3)By studying the role of EPS in the remediation of phenanthrene-contaminated soil with the fusion strain F14,the degradation effect on phenanthrene,soil FDA enzyme activity,and functional group components were analyzed.The study showed that the degradation rate of soil contaminated with phenanthrene at high concentration was overall lower than that at low concentration by 35 d of incubation,and the degradation rate was significantly higher in the experimental group that added the mixture of F14 bacterial solution and EPS than in the experimental group that added F14 bacterial solution.This indicates that EPS helps to improve the degradation effect of fusion strain F14 on phenanthrene,and EPS itself has some degradation effect on phenanthrene.In soils with high pollution levels,EPS can also slow down the effect of excessive concentrations of phenanthrene on the fusion strain F14 and play its protective role.By analyzing the changes of enzyme activity of FDA,it was found that the experimental group that added the mixture of F14 bacterial solution and EPS was at a relatively high level of enzyme activity by 21 d of incubation.This is due to the fact that EPS protects the F14 strain while providing growth and reproduction and metabolism of the strain.FTIR infrared spectra showed that the N-H stretching vibration absorption peaks of proteins,C-O-C stretching vibration absorption peaks and O-H stretching vibration absorption peaks of polysaccharides,as well as the fingerprint region,the intensity of the absorption peaks were significantly changed,and there were individual shifts.(4)EPS has its own degradation effect in the process of fusion strain F14 degradation of phenanthrene,presumably the process may be,first through the hydrophobic effect of EPS polysaccharide and phenanthrene binding,and then use the generated protease to participate in the degradation process,but the number of adsorption sites and enzyme production is limited,its main role of the functional group is hydroxyl,carboxyl,amino.In addition,EPS can protect the strain,provide nutrients when necessary,maintain normal growth and metabolism,and improve the degradation effect.