Both pure culture of R. sphaeroides 2.4 and mixed enriched culture of purple nonsulfur bacteria were used to produce hydrogen with different electron donors acetate, butyrate and a mixture of the two. For each electron source, 3 different nitrogen sources were examined---sodium glutamate, ammonium chloride and molecular nitrogen from headspace nitrogen sparging. The experiments involved a growth phase and a hydrogen production phase.;There was an improvement in both growth and hydrogen production especially for the culture fed with nitrogen sparging when the concentration of the electron source was increased. It was also observed that separate addition of the electron donors led to a difference in the yields versus combined addition for both pure and enriched cultures. Only nitrogen sparged cultures showed a significant difference for separate addition of electron donors when pure culture was compared to mixed culture. For combined addition and comparing pure to enriched culture, there was no significant difference in yields.
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