Biohydrogen Production by Mono- Versus Co- and Mixed Cultures

Acidogenesis and acetogenesis are the key steps in the formation of H2 during the anaerobic decomposition of organic matter. Various groups of H2-producing microorganisms, as well as aspects of their practical use for obtaining biohydrogen as an environmentally friendly fuel, have been studied. In terms of H2 production, the most efficient acidogenic bacteria belong to the genera Clostridium, Enterobacter and Escherichia. They use different fermentation pathways, resulting in different H2 yields and soluble metabolite products. Within the framework of the chapter, we summarized our current knowledge of the diversity of H2-producing thermophilic, hyperthermophilic, mesophilic, and psychrophilic microorganisms and compared their metabolic pathways and cultivation conditions. Mono-, co-, and mixed cultures have different productivity depending on the environmental factors. In the case of co-cultivation, it is important to pay attention to symbiotic relationships of microorganisms, changes in microbial communities, and the development of predominant groups. Ways to enhance H2 production by inhibiting hydrogen consumers and the use of bioaugmentation are discussed. Application of different methods of cultivation and their modifications in order to increase the yield of biohydrogen and the degree of decomposition of organic waste are included.