Screening And Characteristics Of Polycylic Aromatic Hydrocarbons Degradation Fungi

Polycyclic aromatic hydrocarbons are one of the most common pollutants in the environment.They not only damage the ecological environment,but also may cause teratogenic,carcinogenic and mutagenic effects on humans through bioaccumulation.The unique filamentous structure of the fungus allows it to adapt to a particular growing environment and is more prone to survive in compound contaminated environments.They act on PAHs through self-secreted enzymes and extracellular polymer systems.In this study,two strains of highly efficient PAH-degrading fungi were firstly screened to investigate the effect of extracellular enzymes and extracellular polymers secreted by fungi on the degradation of polycyclic aromatic hydrocarbons;secondly,the growth characteristics and tolerance of the strains were investigated.At the same time,the degradation of polycyclic aromatic hydrocarbons was investigated using the mixed strains.Finally,the structure and composition of the extracellular polymeric substances of the strains were analyzed by scanning electron microscopy,total organic carbon analyzer and Fourier infrared spectroscopy.The result is as follows:?1?Screening and identification of the strains:The degrading bacteria AD-X-1 and APD-X-1 were screened with Anthracene as the only carbon source and energy source.Preliminary identif ication by 18S r DNA sequencing:AD-X-1 is Aspergillus flavus,named Aspergillus flavus strain AD-X-1?referred to as AD-X-1?has a GenBank sequence accession number of MG251740 and an accession number of CGMCC No.15392.APD-X-1 is a Penicillium chrysogenum strain named Penicillium chrysogenum strain APD-X-1?abbreviated as APD-X-1?,and the accession number of the GenBank sequence is MG770611,and the preservation number is CGMCC No.15393.Both strains were mainly degraded to remove polycyclic aromatic hydrocarbons,and their extracellular polymeric substances had a certain role in promoting the degradation of anthracene,and lignin peroxidase and manganese peroxidase were involved in the degradation of anthracene.?2?Optimization of the degradation conditions of the strain:The strain AD-X-1 at a temperature of35°C,rotation speed 170 r/min,pH 7 optimum conditions for 72 h degradation rate of the Anthracene up to88%;APD-X-1 Under the optimal conditions of temperature 30°C,rotating speed 170 r/min and pH value7,the degradation rate of anthracene was highest at 65%at 84 h.Tolerance experiment results:The strains AD-X-1 and APD-X-1 can tolerate different concentrations of heavy metal ions(Cu²⁺,Cr³⁺,Pb²⁺,Mn²⁺,Cd²⁺);when the salinity is 9%,The degradation rate of anthracene was still kept at 50%,and the degradation rate of strain APD-X-1 was 32%.In addition to anthracene and phenanthrene,the two fungi also removed tetracyclic Pyrene and Benzo[a]anthracene,The ring of five Dibenzo[a,h]anthracene.When the two fungi were inoculated at a ratio of 1:0.25,the degradation rate was as high as 90%at 72 h;the EPS content was as high as 1389 mg/kg,and the EPS content of a single strain?AD-X-1:1286 mg/kg;APD-X-1:1215 mg/kg?increase signif icant,at a salt concentration of 15%,the degradation rate can be maintained at 48%.?3?Analys is of the strain extracellular polymer:After the anthracene were induced,the total TOC content of the two fungi was 1400 mg/L and 1089 mg/L,the sugars were 880 mg/L and 705 mg/L,and the protein was 540 mg/L.494 mg/L,humic acid 291 mg/L and 183 mg/L,the DNA contents were 5 mg/L and3 mg/L,respectively;the EPS powder structure became loose and porous;The analysis of the stretching vibration of the amino acid C-N,the stretching vibration of–C-O in the phosphate ester and the sugar ring,and the C?N?=O and N-H functional groups in the protein indicate that proteins,polysaccharides,humus,and the like constitute the main component of the EPS.In this study,two strains of alfalfa-degrading bacteria were highly tolerant,and EPS could promote the degradation of the strains.Mixed strains could increase the increase of EPS content and have higher salt tolerance.The strains of this mixed system can be polycyclic aromatic hydrocarbons.Biodegradation provides a reliable strain protection technology.