Study On The Degradation Mechanism Of Pycnoporus Sanguineus To Triphenyl Phosphate And The Toxicity Of Its Degradation Products

Triphenyl phosphate(TPHP)is a typical aromatic organic phosphorus flame retardant,which is widely present in various environmental media and has a variety of toxic effects on organisms.White rot fungi can effectively degrade a variety of aromatic organic pollutants with different structures and have broad application prospects in the field of microbial remediation of aromatic organic pollutants.However,the degradation characteristics and mechanism of TPHP by white rot fungi are still unclear.In this study,TPHP was used as the target pollutant,and Pycnoporus sanguineus was used as a representative strain of white rot fungi to conduct experiments to explore the degradation characteristics,degradation mechanism and bioremediation feasibility of P.sanguineus in the biodegradation of TPHP.The main results of this research are as follows:(1)The best experimental conditions for P.sanguineus to degrade TPHP are:P.sanguineus spore liquid dosage is 5%(V/V),the initial pH of the system is 4-6,and the dosage of glucose is 5 g/L,the concentration of pollutant TPHP is 5 mg/L.(2)A total of 7 TPHP degradation products were detected during the degradation of TPHP by P.sanguineus.Based on the degradation products,it is inferred that the degradation pathways of TPHP mainly involve oxidative cleavage,methylation and hydroxylation.(3)TPHP induces the accumulation of ROS and cell apoptosis in E.coli in a concentration-dependent manner,and TPHP exhibits lower cytotoxicity after P.sanguineus biological treatment.(4)The up-regulation of expression levels of cytochrome P450 enzymes,bifunctional P-450/NADPH-P450 reductase,cytochrome b5,ferredoxin,and aromatic compound dioxygenase indicates that they may be involved in the hydroxylation of TPHP and its degradation products process.The up-regulation of the expression levels of glucose-methanol-choline oxidoreductase,copper radical oxidase,cellobiose dehydrogenase,and Class II peroxidase indicates that they play an important role in the oxidative decomposition of TPHP.The up-regulation of methyltransferase type 11 and S-adenosyl-L-methionine-dependent methyltransferase expression levels indicates that the methylation process of TPHP and its degradation products may be related to the differential expression of these proteins.The up-regulation of MFS transporters indicates that they may play a role in the transmembrane transport of TPHP and its degradation products.In addition,carboxyl esterase and glutathione S-transferase are also activated and may be used to resist the toxic damage caused by TPHP.(5)P.sanguineus is able to resist competition from the native fungal flora and successfully colonize in the water-sediment system,and It also cooperates with the native bacterial flora of Sphingomonas,Burkholderia,Mycobacterium and Methylobacterium to effectively promote the biodegradation of TPHP in the water-sediment system.The metabolic pathways related to the degradation of aromatic compounds,such as aerobic degradation of phenol,?-ketoadipate degradation,and meta-cleavage of aromatic compounds,were significantly enriched in the bioaugmentation group.Arylesterase,phosphodiesterase I,alkaline phosphatase,catechol 1,2-dioxygenase and hydroxyquinoline1,2-dioxygenase were also enriched during bioaugmentation.