Mechanisms for hydrogen production by different bacteria during mixed-acid and photo-fermentation and perspectives of hydrogen production biotechnology

Abstract

H₂ has a great potential as an ecologically-clean, renewable and capable fuel. It can be mainly produced via hydrogenases (Hyd) by different bacteria, especially Escherichia coli and Rhodobacter sphaeroides. The operation direction and activity of multiple Hyd enzymes in E. coli during mixed-acid fermentation might determine H₂ production; some metabolic cross-talk between Hyd enzymes is proposed. Manipulating the activity of different Hyd enzymes is an effective way to enhance H₂ production by E. coli in biotechnology. Moreover, a novel approach would be the use of glycerol as feedstock in fermentation processes leading to H₂ production. Mixed carbon (sugar and glycerol) utilization studies enlarge the kind of organic wastes used in biotechnology. During photo-fermentation under limited nitrogen conditions, H₂ production by Rh. sphaeroides is observed when carbon and nitrogen sources are supplemented. The relationship of H₂ production with H⁺ transport across the membrane and membrane-associated ATPase activity is shown. On the other hand, combination of carbon sources (succinate, malate) with different nitrogen sources (yeast extract, glutamate, glycine) as well as different metal (Fe, Ni, Mg) ions might regulate H₂ production. All these can enhance H₂ production yield by Rh. sphaeroides in biotechnology Finally, two of these bacteria might be combined to develop and consequently to optimize two stages of H₂ production biotechnology with high efficiency transformation of different organic sources.

• Bacteria
• hydrogenases
• hydrogen production biotechnology
• mixed-acid and photo-fermentation
• mixed carbon sources

Acknowledgements

Thank you to all people in the laboratory at the Departments of Microbiology & Plants and Microbes Biotechnology and of Biophysics, Yerevan State University, Yerevan (Armenia), for contribution to the study. Thanks to Ms. Uma Viswanathan for her help in improving the English in the manuscript.

Declaration of interest

The author has no conflict of interest.

The study was conducted within the framework of grants financed by the Ministry of Education and Science of the Republic of Armenia (0167-2005; 1012-2008 and 11F-202-2011) and by grants from the US Civilian Research & Development Foundation (AB1-2307-YE2) and US Armenian National Science and Education Fund (05-NS-microbio-724-10).