Production of Bio-hydrogen by Microorganisms and Extracellular Enzymes: Clean Energy

Abstract

AbstractIntroduction: Hydrogen gas has great potential as a renewable energy source. Although hydrogen gas is obtained from fossil fuels, there is a demand for its production by chemical methods and electrolysis of water, and its extraction from oil sands is currently being studied. Its biological production is one of the cleanest types of hydrogen fuel production due to the consumption of greenhouse gases such as carbon dioxide and/or aerobic and anaerobic fermentation of agricultural wastes, and it can be considered as a solution for simultaneous production of the fuel and elimination of environmental pollutions.Materials and Methods: The present study briefly explains the hydrogen-producing microorganisms, the mechanisms, and the effective enzymes in their production. For this purpose, authoritative articles published between 2006 and 2021 and information in the Scopus database have been used to draw graphs and write this review article. In addition, some limitations and the ways to overcome them for increasing biohydrogen production are described in detail.Results: The results show that carbon dioxide fixation, fermentation, nitrogen fixation, aerobic and anaerobic photosynthesis are some ways of biological production of this fuel.Discussion and Conclusion: Important elements in biological production are the effective enzymes in these reactions and the possibility of using these enzymes in the continuous production of gas, and the purification of hydrogen from other gases. The stabilization of these enzymes under their conditions is of particular importance for the mass production of this gas. Purification of bio-produced hydrogen gas is essential for consumption as fuel, and some technologies, including nanomembranes such as polysulfonate, are very helpful in purifying this gas from other gases such as oxygen, nitrogen, ammonium, hydrogen sulfide, and oxygen.

Keywords

• biohydrogen
• dark-fermentation
• photo-fermentation
• biophotolysis
• bioenergy
• microbial electrolysis