Biodegradation of triphenyl phosphate by a novel marine bacterial strain: Performance, mechanism, bioremediation and toxicity alleviation.

Triphenyl phosphate (TPHP), a widely used organo-phosphorus flame retardant, poses environmental risks due to its persistence and bioaccumulation. In this study, Stutzerimonas frequens RL-XB02, a novel TPHP-degrading strain, was isolated from mangrove sediments. Strain RL-XB02 could completely degrade 50 mg/L of TPHP in 24 hours under various conditions (pH 6.0-9.0, 30-40°C and salinity 2.0-4.0 % (NaCl, w/v)) and the optimal conditions for biodegradation were characterized as pH 7.0, 30°C and salinity 3.0 %. TPHP degradation and growth of RL-XB02 aligned with first-order decay (R2=0.998) and S-Logistic (R2=0.997) model, respectively. Additionally, biofilm formation during TPHP degradation might explain its efficient degradation of hydrophobic compounds. Furthermore, strain RL-XB02 degraded TPHP via enzyme-mediated processes, with intracellular enzymes likely crucial. The metabolites identification and genomic analysis revealed that TPHP was transformed into phenol via stepwise de-esterification, which was assimilated by dual catechol branches of the β-ketoadipate pathway to cell growth. The molecular mechanisms of phenol catabolism were confirmed by RT-qPCR. Bioaugmentation of strain RL-XB02 could eliminate TPHP from marine samples and alleviate the toxicity of TPHP to plants. These findings advance our understanding of TPHP biodegradation pathways and propose a sustainable bioremediation strategy for TPHP contamination.