Isolation Of White Rot Fungus(Trametes Sp.21) And Its Pyrene Degradation Mechanism

With the rapid development of economy,the use and disposal of fossil fuels and petroleum products are increasing,and the emission of PAHs is also increased.Pyrene,as the most abundant typical pollutant in PAH pollution,contains four condensed aromatic rings,which have toxic,carcinogenic and mutagenic effects,which pose serious threat to environment and human health.In view of pyrene pollution in the environment,biological method has been more and more popular in recent years because of its economic efficiency,environmental friendly,and reusability.White rot fungi have unique advantages in the field of PAH degradation because of their lignin decomposing enzyme system,which can completely convert PAHs into carbon dioxide and water.In this study,a white rot fungus was selected qualitatively by plate discoloration reaction,and the laccase conditions of white rot fungi were optimized to study the degradation characteristics of PAH by the crude enzyme of white rot fungus laccase.Meanwhile,the effects of corncob,coffee residue and cottonseed shell as co metabolism substrate were studied.The main results are as follows:(1)A white rot fungus which can secrete lignin degrading enzyme was qualitatively screened by guaiacol,tannic acid and aniline blue plate discoloration test.The strain can secrete laccase and Peroxidase at the same time,but its peroxidase activity is weak and laccase activity is strong.The screened strains were identified by its sequence and identified as Trametes sp.21.(2)Single factor comparison method was used to optimize the medium characteristics and culture conditions for laccase production.The results showed that the optimal medium for laccase production was as follows: corn flour 40 g/L,ammonium tartrate 5 g/L,cobalt sulfate 1 m M,copper sulfate 2 m M,p H = 6.0;The optimal culture conditions for laccase production were as follows: 10%(v/v),30℃,180 rpm,110 m L.After optimization,the highest laccase activity of Trametes sp.21 was 7433 U/L,which was 57 times higher than that before optimization(126 U/L).(3)Plant wastes such as cottonseed hull,corncob and coffee grounds were selected as cometabolic carbon sources for pyrene biodegradation to improve the bioavailability and degradation efficiency of Trametes sp.21.The results showed that plant wastes promoted the growth rate,biomass and pyrene adaptability of Trametes sp.21,and then increased the activity of lignin degrading enzymes and pyrene degradation efficiency of Trametes sp.21.When corncob,coffee residue and cottonseed hull were added,the highest yield of laccase increased by 25,66 and 18 times respectively,and the degradation efficiency of pyrene increased by 53.6%,52.3% and 58.2%respectively.In addition,through the identification and analysis of metabolic intermediates,it is speculated that the pyrene metabolic pathway of the strain is phthalic acid degradation pathway.