Utilization of Methanol plus Hydrogen by Methanosarcina barkeri for Methanogenesis and Growth.

Methanosarcina barkeri grew on methanol plus H(2). Both substrates were consumed in equimolar amounts. Growth was strictly dependent on the presence of acetate, which was required for the biosynthesis of cellular constituents. Only about 0.4% of the methane produced originated from acetate. By using deuterated methanol, it was demonstrated that methanogenesis from this compound under H(2) did not occur via oxidation of methanol to CO(2) and subsequent reduction but by direct reduction with H(2). Growth yields with methanol plus H(2) and with methanol alone were not significantly different: 2.8 g of cells per mol of methanol in mineral medium and 4.6 g of cells per mol of methanol in complex medium, respectively. Growth of M. barkeri on methanol plus H(2) depended strictly on the presence of sodium ions in the medium. In the presence of 50 mM K the K(s) for Na was 5 mM.