Abstract

One of the major challenges of the twenty first century, is keeping up with the growth in global energy demand due to increasing population and rising living standards An alternative for this problem is molecular hydrogen (H 2 H 2 has a high combustion heat per weight unit 142 kJ g 1 and since water is the only by product generated by oxidative combustion it’s an environmentally friendly alternative to fossil fuels H2 can be produced via thermo chemical and biological technologies In this regard, anaerobic fermentation has several advantages compared with other biological methods of hydrogen production because unlike microalgae is independent of light, has a low net energy input and uses low value waste as raw materials Clostridium acetobutylicum is a strictly anaerobic microorganism that can produce H 2 Its fermentation is characterized by two stages, namely, acidogenic stage (acetic and butyric acid production), solventogenic stage (butanol, and ethanol production, Figure 1 the latter leads to spore formation Solventogenic stage and sporogenesis are detrimental for H 2 production This can be avoided by using a degenerate strain unable to produce solvents and to sporulate Degeneration is achieved by the loss of genes present in the megaplasmid pSOL1