Effects of rhamnolipids on the removal of 2,4,2,4-tetrabrominated biphenyl ether (BDE-47) by Phanerochaete chrysosporium analyzed with a combined approach of experiments and molecular docking

Effects of rhamnolipids on the removal of 2,4,2,4-tetrabrominated biphenyl ether (BDE-47) by Phanerochaete chrysosporium (P. chrysosporium) had been investigated, as well as the influence of carbon source (i.e. glucose). The results showed that the removal efficiency was over 90% in all treatments in 7 d. Rhamnolipids at low concentrations (0.05 and 0.1 CMC (critical micelle concentration)) could promote the removal of BDE-47, however, the inhibition effects occurred at high concentrations (0.5 and 1.0 CMC). The further study indicated that rhamnolipids at low concentrations not only promote the growth of mycelium, but also had obvious promotion on ligninolytic enzymes activity (i.e. manganese peroxidase (MnP), lignin peroxidase (LiP) and laccase (Lac)), especially for MnP and Lac. However, the opposite effect was generated at high rhamnolipids concentrations. Meanwhile, glucose played an active role for BDE-47 removal. For better understanding the degradation mechanism, the degradation product analysis and molecular docking had been introduced to this study. The degradation product analysis indicated that OH-PBDEs were the major degradation products and hydroxylation should be the important degradation pathway. The docking results showed that the ideal binding conformation occurred between ligninolytic enzymes and BDE-47, and hydrophobic interactions were the main interaction. Moreover, hydrogen bonds and hydrophobic interactions both existed in ligninolytic enzymes and rhamnolipids interaction. That might be the reason that rhamnolipids affected enzymes activity. These results indicated that P. chrysosporium might be a type of ideal microorganisms in the removal of BDE-47 pollution, and rhamnolipids could be a type of additives for better removal efficiency.