Role Of Extracellular Polymers Of Soil Microorganisms In The Degradation Of PAHs Under Heavy Metal Stress

Microbial exopolysaccharide is a type of organic macromolecule polymer secreted by bacteria or fungi in vitro.It is widely used in environmental engineering,food industry,mining engineering and other fields due to its unique physicochemical properties.At present,microbial remediation of contaminated soils in the field of environmental engineering,such as composting,phytoremediation,joint repair of plants and microorganisms,can not be separated from the role of microorganisms.With the deepening of researches on bioremediation of contaminated soils,the role of extracellular polymers in pollutant removal has drawn more and more attention.The use of extracellular polymers in the remediation of contaminated soils,most of them are the removal of heavy metals from extracellular polymers in contaminated soils,mainly from special bacteria and activated sludge.There is little research on the role of extracellular polymeric substances in the removal of organic pollutants from soil under heavy metal stress.This topic mainly studied the degradation of PAHs by microorganisms under heavy metal stress,the characterization of microbial extracellular polymers and the action of dioxygenase in the degradation of PAHs.The conclusions are as follows:(1)The removal of pyrene by Mycobacterium and Pseudomonas was studied at different concentrations of copper ion lead ions.The results showed that mycobacterium had the highest degradation rate of pyrene when the lead ion concentration was 40 mg/L 76.2% and 75.625% respectively);Pseudomonas had the highest degradation rates of pyrene(73.75% and 65.5%,respectively)with copper ions 80 mg/L and lead ions 40mg/L.(2)Mycobacterium extracelluar polymer was extracted under different concentrations of copper ions and lead ions.The contents of protein,carbohydrate,humic acid and DNA were determined by environmental scanning electron microscopy,three-dimensional fluorescence spectroscopy and spectrophotometer.The extraction amount and main components of mycobacterium EPS were analyzed under different concentrations of copper ions and lead ions.Concluded: 40 mg /L etal ions under the stress of the EPS components and the highest extraction.(3)By comparing 16 S DNA and dioxygenase genes of mycobacteria with different concentrations of two ions,it was found that Mycobacterium tuberculosis had good adaptability to lead ion of copper ion.