Co-metabolic Degradation Of Pyrene By White-rot Fungus Pseudotrametes Gibbosa

With the rapid development of science and technology, people's living standards have been improved, at the same time, it generated a lot of toxic and hazardous substances such PAHs. Microbial biodegradation, as a friendly and effective method of removing these compounds from polluted sites, has been studied extensively. Since the HMW PAHs solubility decreases and hydrophobicity increases with an increase in number of fused benzene rings, they are degraded by co-metabolism. White rot fungi, as highly efficient degrading strains, have been successfully applied in the co-metabolic degradation of HMW PAHs with non-specific extracellular degradation.In this paper, the indigenous white-rot fungus Pseudotrametes gibbosa isolated from Changbai Mountain located in northeast China was used to degrade pyrene, and 6 co-substrates were selected as co-metabolic carbon and energy sources. Pseudotrametes gibbosa was able to utilize pyrene as sole carbon and energy source. Through the screening of six co-substrates (corn flour, wheat bran, sawdust, glucose, salicylic acid, phthalic acid), the highest pyrene biodegradation efficiency (50.64%) was obtained when adding wheat bran to the system and increased by 22.31% compared with the control (28.33%) 18 days after adding pyrene. Glucose, corn flour and sawdust played a promotive role on the degradation of pyrene. However, phthalic acid and salicylic acid inhibited the degradation of pyrene. The research on degradation mechanism found that there was some correlation between enzyme activity and degradation ability, in other words, the higher the Lac activity was, the better the degradation efficiency of pyrene was.Through the optimization of the culture condition for the co-metabolic degradation of pyrene by orthogonal test, we obtained the scheme of optimum culture condition, which was made up of wheat bran with the concentration of 20g/L, three fungus discs and 50mL liquid culture without ABTS. Influence sequence of every factor of Pseudotrametes gibbosa's producing laccase was:RB>RC>RA>RD. The amount of fungus dies was the most influential factor for producing laccase by Pseudotrametes gibbosa, the volume of liquid culture and the concentration of wheat bran next to, the concentration of ABTS finally. Optimal Lac activity of the medium was up to 53.41U/mL, which was 18.8 times higher than the traditional medium, so the optimal culture medium has a great advantage for application. Additionally, most of the degradation dates of pyrene by Pseudotrametes gibbosa were higher than 50%, even up to 88.8%.Through identifying intermediate products of pyrene after optimized medium were, we obtained 6 stable metabolites, which were Phenanthrene,Fluorene,4-Amino-9-fluorenore,9,10-Anthracenedione,1,4-Naphthalenedione andphthalic acid. With the extension of degradation time, all kinds of metabolic intermediate products increased firstly and then decreased. On the 12th day, there were most types of intermediate products.According to the appraisal of intermediate products, we inferred to the final pathway which may be phenanthrene metabolic pathways via ring-opening reaction and decarboxylation reaction.