Deeply mechanism analysis of hydrogen production enhancement of Ethanoligenens harbinense by Fe2+ and Mg2+: Monitoring at growth and transcription levels

For deeply understanding the H2 production promotion mechanism by adding Mg2+ and Fe2+ in Ethanoligenens harbinense fermentation process, the effects on cell growth, liquid byproducts production and H2 yield at growth level were investigated, meanwhile the expressions of [FeFe]-hydrogenase, acetate kinase, alcohol dehydrogenase and lactate dehydrogenase with quantitative reverse transcription PCR at transcript level were monitored. The experimental results indicated that Mg2+ makes more contributions on cell growth, but with Mg2+ concentration increasing the expressions of functional genes were obviously suppressed. Fe2+ has slightly positive effects on increasing cell growth and functional genes expression, which is inferred the reason of H2 production enhancement. A maximum hydrogen yield of 2.14 mol-H2/mol-glucose was obtained in optimal medium supplemented with 600 mg/l MgCl2·6H2O and 100 mg/l FeSO4·7H2O. The realization of hydrogen production enhancement of E. harbinense by adding promoting factors was not only realized through increasing cell biomass growth and hydrogenase activity, but also some promotion effects on functional enzyme genes expressions.