Efficiency of photo-hydrogen production is highly dependent on the culture conditions. Initial pH, temperature were optimized for maximal hydrogen production using response surface methodology with central composite design. Photo fermentative hydrogen production is influenced by several parameters, including pH and temperature. Rhodobacter sp. KKU-PS1 was isolated from the methane fermentation broth of an UASB reactor. This study presents the experimental results obtained from Rhodobacter sp. KKU-PS1 cultures as a function of temperature and pH. For this purpose, a complete factorial design was used, for the temperatures of 26, 30 and 34°C and the pH of 6.5; 7 and 7.5. Rhodobacter sp. KKU-PS1 has been isolated from the fermentation of methane. Optimum conditions for maximizing cumulative hydrogen production (H max) were an initial value of pH 7.0 and a temperature of 25°C. The regression models revealed a maximum hydrogen production of 1623 ml at these conditions. KKU-PS1 can produce hydrogen from organic acids. By optimizing the pH and the temperature, a maximal production of hydrogen by this strain was obtained. Validation experiments at calculated optima confirmed these results.

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