Transformation of tetrabromobisphenol A by Rhodococcus jostii RHA1: Effects of heavy metals

Abstract

Tetrabromobisphenol A (TBBPA) is one of the most widely used brominated flame retardants in the world but it is also a pollutant of global concern. In the present study, we studied the transformation of ¹⁴C-labeled TBBPA by a polychlorinated-biphenyl-degrading bacterium, Rhodococcus jostii RHA1 (RHA1), under oxic conditions. During the 5-day incubation, TBBPA was biotransformed rapidly first to its monomethyl ether MeO-TBBPA and then to its more hydrophobic but less toxic dimethyl ether diMeO-TBBPA. The biotransformation followed pseudo-first-order decay kinetics, with a half-life of TBBPA of 0.32 days and only 0.6% of the initially added amount being mineralized. Considering the frequent co-occurrence of TBBPA with heavy metals in the natural environment, we also investigated the effects of three heavy metals (Cd, Cu, and Fe) on the transformation of TBBPA by strain RHA1. While TBBPA transformation was not significantly altered by Cd, it was accelerated by Cu and Fe, presumably due to the effects of these two essential metals on O-methyltransferase activity. Overall, the present study showed that RHA1 is an effective transformer of TBBPA and that certain essential metals, including Cu and Fe, promote the transformation.

Keywords: Heavy metals; O-methylation; Rhodococcus jostii RHA1; Tetrabromobisphenol A.