Co-metabolic degradation of tetrabromobisphenol A by Pseudomonas aeruginosa and its auto-poisoning effect caused during degradation process.

In this study, Pseudomonas aeruginosa was applied to degrade tetrabromobisphenol A (TBBPA) with glucose as a co-metabolic substrate. Influencing factors of co-metabolic degradation such as pH, TBBPA and glucose concentration were examined and the degradation efficiency under optimal condition reached about 50% on the 7th day. The study also proved that the extracellular action, rather than intracellular one, played a leading role in TBBPA degradation. Five metabolites including debromination and beta-scission products were identified in this study. The extracellular active substance pyocyanin was considered as the origin of H2O2 and OH·. The variation of concentrations of H2O2 and OH· shared the same trend, they increased in the early days and then declined gradually. On the 1st day, the OD600 of P.aeruginosa in the co-metabolic group was 6.0 times higher than the initial value while total organic carbon (TOC) decreased about 78%, which might lead to the occurrence of pyocyanin auto-poisoning. Flow cytometry was applied to detect the cellular state of P.aeruginosa during degradation. The increasing intracellular ROS showed that cells were suffering from oxidative stress and the change of membrane potential revealed that cellular dysfunction had occurred since the 1st day. This research indicated that the toxic effect on P.aeruginosa was probably not directly correlated with TBBPA, but was caused by pyocyanin auto-poisoning.

Identification of novel pathways for biotransformation of tetrabromobisphenol A by Phanerochaete chrysosporium, combined with mechanism analysis at proteome level.

The investigation of tetrabromobisphenol A (TBBPA) removal by Phanerochaete chrysosporium (P. chrysosporium) was conducted. Under optimal conditions (pH 5, inoculum size of 5% (v/v), initial glucose concentration of 5 g/L, TBBPA concentration of 5 mg/L), >97% of initial TBBPA was removed after 3 days. The TBBPA metabolites, tetrabromobisphenol A glycoside, tribromobisphenol A glycoside and monohydroxylated tetrabromobisphenol A, were identified for the first time by fungi transformation as being produced by glycosylation and oxidative hydroxylation, respectively. Proteome analysis showed that P. chrysosporium significantly upregulated cytochrome P450 monooxygenase, glutathione S-transferases, UDP-glucosyltransferase, O­methyltransferase and other oxidoreductases for TBBPA oxidative hydroxylation, reductive debromination, glycosylation, O­methylation and oxidative cleavage for detoxification. Data from cytotoxicity tests with human hepatocellular liver carcinoma (HepG2) confirmed that TBBPA toxicity was effectively decreased by P. chrysosporium treatment. Bioaugmentation with P. chrysosporium significantly improved the removal efficiency of TBBPA in water microcosms to 63.1% within 12 h. This study suggests that P. chrysosporium might be suitable for the removal of TBBPA from contaminated water.