Effect of Fluoroacetates on Methanogenesis in Samples from Selected Methanogenic Environments

Trifluoroacetic acid (TFA) is an atmospheric decomposition product of a new generation of refrigerants that will replace current ozone-depleting CFCs. The effect of trifluoroacetic acid on microbial methanogenesis was assessed using environmental samples from four distinct methanogenic systems: the anaerobic digestor, the rumen, freshwater sediments, and marine sediments. TFA exhibited no toxcity, as evidenced by the rate of methanogenesis, at concentrations up to 10 mM. [1-14C]TFA was used to test for biodegradation (release of 14CO2) in methanogenic marine sediments. No significant release of 14CO2 was observed. As a control, the toxic monofluoroacetate (MFA), which is not an atmospheric degradation product of CFC replacements, was found to inhibit methanogenesis in freshwater and anaerobic digestor samples at or above concentrations of 0.1 mM. We conclude that TFA is inert in these methanogenic systems and there is no evident toxicity to either the methanogenic or fermentative populations.