Studies On The Removal Of 2,2',4,4'-tetrabromodiphenyl Ether With Peroxidases Secreted By White Rot Fungi Phanerochaete Chrysosporium

Polybrominated diphenyl ethers (PBDEs) are flame retardants that have been widely integrated into textiles, plastics and electricity appliances for several decades. They are easily released into the environment from various commercial goods and caused pollution for their special physicochemical properties. Because of their bioaccumulative property and endocrine disrupting activity, the presence of PBDEs in the environment has potentially threatened the whole ecosystem and human health. 2,2',4,4'-tetraBDE(BDE47) which is currently the most widely distributed, with the highest concentrations in biological samples, and one of the most toxic polybrominated diphenyl ether congeners in living organisms and human beings attracts more and more attention. White rot fungi, which have high efficient and nonspecific degradation capacity to compounds with lignin structure, are widely applied on the removal of different kinds of recalcitrant pollutants. As biodegradation is an important pathway in the environment fate of PBDEs, it is of great significance to study the biotransformation of BDE47 with white rot fungi and their peroxidases.In this paper, we first explored the optimized cultivating conditions for white rot fungi to selectively excret manganese peroxidase (MnP) and its purification method, and then studied the removal efficiency of BDE47 with the white rot fungi cell culture, concentrated LiP, and MnP separately. The effects ofβ-CD and Tween80 on the removal of BDE47 by white rot fungi cell culture and the effects of phenol and NOM on the removal of BDE47 with the concentrated LiP and MnP were further investigated.The main results obtained from the studies are as follows:(1) Through comparative tests, we got the optimal cultivating condition of white rot fungi to selectively excret MnP:Tween80(0.05%, v/v), agitated culture(37℃,150r/min), and the MnP activity reached the maximum of 2141.67U/L at the 11th day after incubation. Effective separation of MnP and LiP was achieved by adding Tween80 and increasing the amount of Mn2+.(2) The average removal efficiency of BDE47 in the white rot fungi cell culture system was about 70% after incubation for 15 days; In early days of the incubation, some of the BDE47 were adsorbed by the mycelium, but the adsorption was under the detection limits in later period. The contribution of P450 enzyme on the degradation of BDE47 were also examed and no effect of P450 on the biodegradation of BDE47 were observed.(3) Addition of Tween80 andβ-CD in the cell culture system were studied, and no significant effects were observed on the removal efficiency of BDE47 no matter by adding Tween80 orβ-CD, which might be mainly because of the relatively high bioavailability of BDE47 which made the solubilization effects of Tween 80 andβ-CD on the apparent solubility of BDE47 not significant.(4) The role of purified LiP and MnP on the removal of BDE47 was also investigated. The effect of phenol and natural organic matter (NOM) on enzymatic reaction of BDE47 revealed that phenol and NOM have different effects on the LiP and MnP reaction. In the experiment concentration, phenol and NOM could increase the removal efficiency of BDE47 and removal efficiency is parallel with the concentration of phenol and NOM for LiP. The removal efficiency of BDE47 is achieved:33.6% without phenol and NOM,41.3% with 2mM phenol,47.5% with lOmM phenol,56.1% with 50mM phenol,51.3% with 20mg TOC/L and 53.5% with 50mg TOC/L. However, for MnP, the enhancement effects were increased at low concentration and decreased at high concentration both with phenol and NOM, but the removal efficiency of BDE47 was still higher than the system without phenol and NOM, it is achieved: 4.2% without phenol and NOM,18.1% with 2mM phenol,22.9% with lOmM phenol,8% with 50mM phenol,38.8% with 20mg TOC/L and 24.6% with 50mg TOC/L.