Relation between pH, Hydrogenase and Nitrogenase Activity, NH+4 Concentration and Hydrogen Production in Cultures of Rhodobacter Sulfidophilus Peng, Y. and Stevens, P. and De Vos, P. and De Ley, J.,, 133, 1243-1247 (1987), doi = https://doi.org/10.1099/00221287-133-5-1243, publicationName = Microbiology Society, issn = 1350-0872, abstract= Rhodobacter sulfidophilus, a sulphide-tolerant, salt-tolerant member of the Rhodospirillaceae, was shown to produce molecular hydrogen on a mineral medium with lactate as electron donor and glutamate as nitrogen source. A maximum production of about 1·1 mmol H2 (mmol added lactate)−1 was found at pH 6·75. The in vivo activity of hydrogenase and nitrogenase showed that hydrogenase activity (and thus the H2 recycling system) was greatest at pH 6·5 and 6·75 and thus, at least partially, was responsible for the lack of H2 production below 6·75, but that nitrogenase activity was greatest at between pH 6·5 and 7·0, and decreased to zero at pH 8·0, resulting in reduced H2 production at pH 7·5 and none at pH 8·0. When sufficient NH+ 4 had accumulated in the culture, nitrogenase activity remained below the maximum value and no H2 production occurred., language=, type=