Abstract
The hydrogen evolution from ethanol, n-propanol, n-butanol, malate and mixed substrates containing these compounds by Rhodopseudomonas sp. No. 7 was examined. A small amount of bicarbonate was necessary for the commencement of the hydrogen evolution in an alcoholglutamate medium by the bacterium grown in an alcohol-NH+4 medium. Bicarbonate added to the medium was a concentration of less than one-tenth of that required for the maximum growth in the alcohol-NH+4 medium. Once the cells had acquired the ability of hydrogen evolution, they continued to evolve hydrogen regardless of the presence or absence of bicarbonate. The rate and the yield of the evolution were improved in a medium containing both an alcohol and malate. These substrates were not preferentially but simultaneously consumed in the mixed medium. The alcohols and malate were effective for the evolution when the electron donors were used at low concentrations and when the incubation temperature was elevated to 40°C, respectively. The yield and the rate of the evolution at 40°C were 70% and 80μl/mg cell/hr, respectively. The bacterium incubated in a medium containing an alcohol exhibited a higher level of glutamine synthetase than that in the malate-medium.
