Do anaerobic-aerobic alternating strategies regulate microbial degradation of BDE-209 in soils?

The primary natural attenuation pathways for decabromodiphenyl ether (BDE-209) are anaerobic reductive debromination and aerobic oxidation, yet microbial degradation efficiency under anaerobic-aerobic alternating strategies remains poorly understood. We established the XH1 consortium and systematically evaluated BDE-209 degradation over 8 weeks under various alternating conditions. The results showed that the XH1 consortium degraded BDE-209 faster under alternating anaerobic-aerobic conditions, compared with continuous aerobic or anaerobic degradation. The greatest degradation efficiency of 70 % was observed in the 4:4 (anaerobic: aerobic) alternating strategy. Microbiological analyses showed that the 4:4 strategy up-regulated the expression of key dehalogenase genes (2-Haloacid dehalogenase and Haloalkane dehalogenase genes), which were suppressed by frequent redox switching in the 1:1 cycle. Degradation efficiency was found positively correlated with aerobic duration (R²=0.39, p = 0.04), and the prolongation of the aerobic phase activated the dioxygenase system. The cyclic alternation strategy indicated that a lower frequency of alternation contributed to the expression of dehalogenase genes. Overall, this study combines microbial metabolic diversity with enhanced environmental adaptability by modeling natural environmental dynamics. It provides an efficient and sustainable approach for the treatment of BDE-209 contamination.