Enhanced Aerobic Degradation Of Low Chlorinated Biphenyls By Constructing Surfactants-Burkholderia Xenovorans LB400 Based System

Polychlorinated biphenyl is typical hydrophobic organic pollutant which is characteristic of extremely low water solubility and hard biodegradability. It has been proposed that the increasing of water solubility of PCBs can enhance the biodegradatio n efficiency. The biodegradation system of PCBs by Burkholderia xenovorans LB400 in the presence of different surfactants, namely TX-100, Tween 80, RL crude and HPCD were established to investigate the effect of surfactants on the biodegradation of hydrophobic organic compounds. The results indicated that the water solubility ratios of PCB5 and PCB31 were 54.7%-100%, 59.8%-100%; 10.5%-40.8%, 6.8%-31.6%; 10.3%-19.9%, 3.3%-11.6% and 19.5%-34.2%, 4.2%-10.7%, which were accordingly enhanced by TX-100(CMC=194 mg·L-1), Tween 80(CMC=13.1 mg·L-1), and RL crude(CMC=50 mg·L-1) with concentrations of 1-7 CMC, respectively and HPCD with concentrations of 500-1500 mg·L-1. Moreover, the growth inhibition ratio of B. xenovorans LB400 was 30.3%-45.8% with TX-100 concentration of 1-7 CMC, while it was 10.0%-15.4% for Tween 80 with concentration of 0.1-1 CMC; RL crude could boost the growth of strain LB400 as substrate while HPCD exerted no impact on it. The addition of surfactants can improve the biodegradation ratios of PCB31(5 mg·L-1) by 23.7%-65.5% for TX-100, 14.6%-44.3% for Tween 80, 9.6%-27.2% for RL crude and 15.3%-20.7% for HPCD depending on the surfactant concentrations, while it had minor effects on the biodegradation ratios of PCB5(10 mg·L-1). It is concluded that the promoting effects of surfactant on PCBs biodegradation are mainly due to the increased concentrations of PCBs-surfactant micelles in aqueous solution and when TX-100 and Tween 80 concentrations are set as 1 and 7 CMC, the biodegradation ratios of PCB31 can achieve 100% and 81.7%, while the growth inhibition ratios of B. xenovorans LB400 are 30.3% and 5.4%, respectively.The desorption ratios of PCB31 in soil environment were 10.49%, 31.99% and 53.22%, which were enhanced by TX-100 with concentration of 5, 10 and 20 g·L-1, respectively, while for Tween 80 with concentration of 10 and 20 g·L-1, the desorption ratios of PCB31 were 4.31% and 26.47%. For application of B.xenovorans LB400-surfactant combined system in PCB31 degradation in soil, after B. xenovorans LB400 got adapted to the environment of high concentration Tween 80(≥1 g·L-1), it could degrade PCB31 rapidly and achieve nearly 100% removal rates within 4 d. Although the high concentration of TX-100(≥1 g·L-1) exerted continuous inhibiting effect on PCB31 degradation by B. xenovorans LB400, however, the removal rates of PCB31 were still very apparent.