Effect of redox potential on methanogenesis by Methanosarcina barkeri

Abstract

Concentrations of 0.5% O2 immediately inhibited CH4 production from methanol by Methanosarcina barkeri. Simultaneously, the redox potential of the medium increased to about +100 mV. However, the rates of CH4 production were not significantly affected, when the redox potential of an anoxic medium was adjusted to values between -420 mV and +100 mV by addition of titanium (III) citrate, sodium dithionite, flavin adenine dinucleotide, or sodium ascorbate. When the redox potential was adjusted to values between -80 mV and +550 mV by means of mixtures of ferrocyanide and ferricyanide, CH4 production was not inhibited until a redox potential of about +420 mV was reached. M. barkeri was able to reduce 0.5 mM ferricyanide solution at +430 mV within 0.005%.