Substantial defluorination of polychlorofluorocarboxylic acids triggered by anaerobic microbial hydrolytic dechlorination

Chlorinated polyfluorocarboxylic acids (Cl-PFCAs) derived from the widely used chlorotrifluoroethylene oligomers and polymers may enter and influence the aquatic environment. Here we report the substantial defluorination of Cl-PFCAs by an anaerobic microbial community via novel pathways triggered by anaerobic microbial dechlorination. Cl-PFCAs first underwent microbial reductive, hydrolytic and eliminative dechlorination, with the hydrolytic dechlorination leading to the highest spontaneous defluorination. Hydrolytic dechlorination was favoured with increased Cl substitutions. An isolated, highly enriched, anaerobic defluorinating culture was dominated by two genomes that were most similar to those of Desulfovibrio aminophilus and Sporomusa sphaeroides, both of which exhibited defluorination activity towards chlorotrifluoroethylene tetramer acid. The results imply that anaerobic non-respiratory hydrolytic dechlorination plays a critical role in the fate of chlorinated polyfluoro chemicals in natural and engineered water environments. The greatly enhanced biodegradability by Cl substitution also sheds light on the design of cost-effective treatment biotechnologies, as well as alternative polyfluoroalkyl substances that are readily biodegradable and less toxic. Physicochemical defluorination is arguably the best pathway to degrade polyfluoroalkyl substances. In the case of chlorinated polyfluorocarboxylic acids, it is shown that substantial defluorination can be achieved by an anaerobic microbial community via novel pathways triggered by anaerobic hydrolytic dechlorination.