Metabolisms Of Phenanthrene And Benzo[a]anthra Cene Biodegradaiton By Wood Rot Fungus Pycnoporus Sangui Neus H1

PAHs,which are composed of two or more benzene rings by means of alignment,bending and clustering,are produced by the incomplete combustion of coal,oil and natural gas and distribute in the environment widely.PAHs have three kinds of persistent organic pollutantants including carcinogenicity,mutagenicity and teratogenicity.Therefore,how to remove PAHs in the environment has aroused more and more concerns.White rot fungus are able to degrade PAHs,so that it is expected to become the ideal compound which can remediate PAHs contaminated soil.However,now the degradation mechanism is unclear.In this study,tricyclic phenanthrene and tetracyclic benzo[a]anthracene as model compounds are used to explore not only the degradation rate and degradation characteristics of white rot fungus but also biotransformation mechanisms of PAHs.And the results of this study lay a theoretical foundation of finding the actual repair agents which can degrade PAHs.The main contents and results are following:This study selected the pre-isolated four white rot fungi and then detected their enzyme activities.The results showed the 14 strains had the highest value which reached 2516.67 U/L in the 6th day.According to the degradation screening of phenanthrene and benzo[a]anthracene by Pycnoporus sanguineus H1(14 strains),the results demonstrated benzo[a]anthracene had the best degradation rate of 96.17% and the degradation rate of phenanthrene was 45%.The process that fungus degraded phenanthrene and benzo[a]anthracene can produce persistent production of Laccase.The results showed that production of laccase and the degradation of benzo[a]anthracene had positive correlation.By GC-MS,it was detected that the metabolites of phenanthrene maybe phenol derivatives and benzo[a]anthracene metabolites maybe cyclohexane,1-amino-2-naphthalenol,naphthalene or 4-acetylbenzoic acid.After the analyzation of the transformation of phenanthrene and benzo[a]anthracene by extracellular enzyme system of Pycnoporus sanguineus H1,it was found that phenanthrene was transformed by extracellular enzyme fluid,but the transformation rate was not improved after adding H2O2 and Mn2+,H2O2,ABTS.And during the process of the transformation by mycelium and homogenized mycelium of Pycnoporus sanguineus H1,the transfomation rate of phenanthrene was not changed when ABT,which was an inhibitor of P450,was added in the system.The results above indicated that the phenanthrene can not be transformed by Fungal Lac,Mn P,Li P and P450,so that there might be other metabolic pathways which can transform phenanthrene.When adding H2O2 and Mn2+,ABTS,that the transformation of benzo[a]anthracene was improved by extracellular fluid,which indicated the transformation of benzo[a]anthracene depended on the Mn P and Lac.To improve the production of hydroxyl radicals by the mycelium of Pycnoporus sanguineus H1,DBQ and Fe3+–EDTA were added.The results showed that the increase of hydroxyl radical helped improve the transformation of phenanthrene and benzo[a]anthracene.A large increasing number of mycelium can also rise the production of hydroxyl radicals.The effects of adding different common metabolic substrates such as wheat bran,straw,sawdust on the enzyme activity were analyzed and the results showed that there was a negative correlation which meaned the more hydroxyl radicals were consumed,the higher the production of Lac and the degradation rate of Pycnoporus sanguineus H1.In summary,the degradation of benzo[a]anthracene by Pycnoporus sanguineus H1 is the best.The main degradation pathway is realized by extracellular Lac.However,the degradation pathway of phenanthrene remains to be a further study.Pycnoporus sanguineus H1 can produce small amounts of hydroxyl radicals during the process of the degradation of phenanthrene and benzo[a]anthracene and the consumption of hydroxyl radicals has a positively correlation with the production of Lac.