Abstract In a two-phase anaerobic digestion system, with separate reactors for the acidification phase and the methane fermentation phase, the glucose of a 1% glucose solution was almost completely converted into biomass and gases. The acid reactor was operated at 30°C and pH 6.0, with a retention time of 10 h. Main products of the acid-forming phase were hydrogen, carbon dioxide, butyrate and acetate. On a molar base, these products represented over 96% of all products formed. On average, 12% of the COD content of the influent was evolved as hydrogen. The effluent of the first reactor was pumped to the methane reactor after passing through a storage vessel. The methane reactor was operated at 30°C, pH 7.8, and a retention time of 100 h was given. Approximately 98% of the organic substances fed to this reactor were converted to methane, carbon dioxide and biomass. About 11% of the glucose fed to the digesting system was converted to bacterial mass.