Biohydrogen production by dark and photo-fermentation processes

The hydrogen can be produced in a biological production process by dark and photo-fermentation of organic substrates. Under anaerobic conditions, hydrogen is produced during conversion of organic substrate into organic acids using fermentative bacteria and during conversion of organic acids into H2and CO2using photo- fermentative bacteria. This bioprocess has been studied with a number of microorganisms, it is a very complex process and influenced by many factors. In order dark and photo-fermentation process is an important approach for bio-hydrogen production. In this study, different factors haves been examined to enhance biohydrogen production by these organisms, either as a combined or sequential using dark and photo-fermentation process. The effect of each factor on biohydrogen production efficiency is reported. A comparison of hydrogen production efficiency between dark-fermentation, photo-fermentation and two stage processes was investigated.