New Insights into the Biodegradation of Organophosphorus Flame Retardants by Microbial Consortium: Mechanism, Risk and Application

Abstract

In this study, triphenyl phosphate (TPHP), a representative organophosphorus flame retardant, could be 100% degraded by isolated microbial consortium ZY1 within 12 h under a wide range of pH, temperature and initial concentration in water. Both extracellular enzymes and intracellular enzymes could completely transform 1 mg/L TPHP and diphenyl phosphate was the major degradation intermediate. The usually coexisted tricresyl phosphate isomers, 2,2',4,4'-tetrabromodiphenyl ether, hexabromocyclododecane, Cd and Cu would significantly inhibit the TPHP degradation. Sphingobacterium, Variovorax and Sphingopyxis in ZY1 were identified as core genera that mediated the transformation of TPHP. Metagenomic analysis revealed that genes coding for cytochrome P450/NADPH-cytochrome P450 reductase, acid phosphatase and alkaline phosphatase were the key genes for TPHP biotransformation. Transcriptome sequencing suggested that the pathway of carbohydrate metabolism and synthesis process of peptidoglycan layer was significantly impaired under the intact TPHP exposure, while the genes related to oxidation stress response were down-regulated when exposed to degradation intermediates mixture, indicating that TPHP degradation by ZY1 was a detoxification process. Finally, the application of microbial consortium for bioaugmentation of TPHP contaminated freshwater and seawater was conducted and achieved excellent effect. This study provided comprehensive  information of developing new bioremediation technology for OPFRs contamination in the environment.

Keywords: Organophosphorus flame retardants, Biodegradation, Metagenome, Toxicity evaluation, Bioaugmentation