White Rot Fungi Screening For PAHs Degradation And Their Degrading Characteristics

In recent decades, with the rapid development of the industry, the mine and use of fossil fuel are also rapidly increasing, synchronously accompanying with the serious pollution of polycyclic aromatic hydrocarbons (PAHs), which threatened human health and the whole ecological environment. Among the control technologies, microbial biodegradation is a friendly and effective means to remove PAHs from the environment, which has been extensively used. White rot fungi,as highly efficient degrading strains, also play an important role in the removal of the PAHs.14 local white-rot fungi,widespread grown in the forest northeast China, were screened for their ability to efficiently degrade PAHs. Through the research on degrading anthracene and enzyme production by 14 white rot fungi, we eventually obtained highly efficient degrading fungus-Polyporellus picipes. The degradation efficiency of anthracene after 16 days of inoculation was 70.00%. The major enzymes secreted by the fungi were Lip, MnP and Lac, and Lac was the main degrading enzyme.Under the degradation conditions, the maximum Lac activity reached 19950.59U/L. The research on enzyme production found that adding anthracene delayed the emergence of the peak and also stimulated Lac secretion.In the presence of anthracene, Lac activity achieved 3043.08U/L which was higher than the non-anthracene.In the study we optimized the Lac secretion conditions by orthogonal test and single factor experiments.After optimizing medium, the main components are 35 g/L wheat bran,4 g/L peptone, pH4.0(Medium other components:1g/L K2HPO4·3H2O,0.5 g/L KCL,0.5g/ L MgSO4·7H2O,0.01g/L FeSO4·7H2O).The maximum activity was 81492.23 U/L and the activity period was more than 30 days. The peak lasted longer. Optimal culture conditions were:the inoculums 3/cp10mm bacterial,the temperature 28℃, rotation speed 160r/min. Another study on the inducer found that,0.25～4μmol/L Cu2+ had promoted enzyme production, but with the concentration increasing, the stimulative role was gradually reduced. The optimal concentration was 0.5μmol/L; low concentration of Tween 80 could promote enzyme production, while high concentration would inhibit enzyme production. The optimal concentration was 0.125 g/L.The degradation efficiency of single and compound PAHs were measured on the 11th, 22nd, and 33rd day after the inoculation under the optimal conditions.The degradation efficiencies of the single anthracene, phenanthrene, pyrene after 33d culture were 94.76%, 96.56% and 57.53% respectively,so the fungus degraded phenanthrene most effectively, followed by anthracene, finally pyrene; To the anthracene+ phenanthrene, anthracene+pyrene two complex PAHs, the degradation efficiencies of phenanthrene and pyrene after 33d culture were 99.46% and 61.09%.The capacity of degrading single PAHs related to the strains structure and their own producing enzyme. The degradations of PAHs in different varieties were different due to the structure of PAHs, which resulting in different use extent. For the same kinds of PAHs, the peak of enzyme production was synchronous with the highest degradation efficiency. The research on degradation of complex PAHs found that adding a small amount of anthracene could enhance the degradation efficiency of phenanthrene and pyrene. Therefore, adding LMW PAHs may achieve more efficient degradation of HMW PAHs.