摘要
Hydrogen （H2） appears as one of the most promising alternative forms of energy supply, as it is non-pollutant and has a high heating value. The production of H2 by non-conventional ways, such as fermentative production, depends on economic factors and the H2 yield achieved in the process. Therefore, this review summarizes the basic aspects of hydrogen production, specifically focusing on the role of the dark fermentation process, as a way to produce this gas by biological means. The different parameters affecting the production of H2 are also discussed. The existence of different hydrogen producing microorganisms with different enzymes causes the necessity to investigate the effect of the conditions under which the process is carried out. Thus, the factors influencing the fermentative process, such as pH, temperature, inoculum pretreatment, hydraulic retention time, hydrogen partial pressure and substrate composition （metal ions, nitrogen source, etc.） are summarized.
