Biotransformation and biodefluorination of chlorinated polyfluorocarboxylic acids by Acetobacterium species

Chlorinated per- and polyfluoroalkyl substances (Cl-PFAS) represent an important subgroup in replacement chemicals for legacy PFAS, and they have been detected in various environments including water bodies, soil, as well as air particles. However, the biodegradability of these chemicals is largely unknown. A recent study reported dechlorination triggered anaerobic biodefluorination of Cl-PFCAs by activated sludge communities. In this study, we further investigated the biodefluorination of Cl-PFCAs by pure cultures. Six of ten selected Cl-PFCAs displayed significant defluorination by Acetobacterium bakii, and corresponding pathways were proposed according to transformation product analysis. Several additional Acetobacterium species were all capable of defluorinating 3,5,7,8-tetrachloro-2,2,3,4,4,5,6,6,7,8,8-undecafluorooctanoic acid (CTFE4) with >50% removal of organic fluorine. On the contrary, Clostridium homopropionicum cannot defluorinate CTFE4. Crude protein extraction experiment showed that the enzymes responsible for CTFE4 dechlorination and defluorination required anaerobic atmosphere to function. Differential gene expression was analyzed according to RNA sequencing analysis, and the results indicated vitamin B12 related enzymes may involve in CTFE4 dechlorination.