Inhibitory effects of saturated fatty acids on methane production by methanogenic Archaea

The present study investigated the inhibitory effects of saturated fatty acids on methanogenesis in Archaea, and whether or not competitive inactivation of the methanogens’ coenzyme M (HS-CoM) is involved in the inhibition. Strains tested in batch cultures were Methanosarcina barkeri, Methanosarcina mazei, Methanococcus voltae, all incubated at 37°C, and Methanothermobacter thermoautotrophicus, incubated at 65°C. The fatty acids C₁₀, C₁₂, C₁₄ and C₁₈ were supplemented at 1 mg · ml^–1 in cultivation medium. The methanogens were susceptible to C₁₀ and C₁₂, and less so to C₁₄. Only M. thermoautotrophicus was affected by C₁₈. In M. mazei cultures, excessive HS-CoM did not prevent the action of C₁₄ which might suggest that competitive inhibition of HS-CoM is not the reason for the SFA-induced effect on methanogenesis. The results indicate that, as a prerequisite to inhibit methanogenesis in Archaea, medium- and long-chain saturated fatty acids have to be at least partially molten.