ABSTRACT

The processes of methane production in bottom muds containing sea water sulfate were investigated in relation to both sulfate reduction and organic acid fermentation. The methane production in bottom muds was dependent on the degree of sulfate reduction, and did not occur until about 80% of sea water sulfate was removed by sulfate reduction. The activity of methane production in bottom muds was not inhibited even under the sulfide-S concentration of 160mg per 100g wet mud, and was directly dependent on the amount of organic acids. When the bottom mud added with phyto-plankton was incubated at 20°C for 20 days, sulfate decreased with consumption of lactic acid, and acetic and propionic acids were formed as the successive metabolites of lactic acid. Of the three organic acids added individually to bottom muds, lactic acid was utilized as hydrogen donor for the sulfate reduction, and acetic and propionic acids were produced with the passage of sulfate reduction. Acetic and propionic acids were not utilized for the sulfate reduction, but they were converted into methane, when the degree of sulfate reduction attained more than 80%.