A review of green biohydrogen production using anoxygenic photosynthetic bacteria for hydrogen economy: Challenges and opportunities.

Among multiple alternative clean and renewable energy sources, hydrogen is the most promising green fuel because of its high conversion efficiency, energy potentiality, and sustainability. In this review, green biohydrogen production by anoxygenic photosynthetic bacteria (APB) is summarized with the aim to enhance the present understanding of the underlying mechanisms and to gain a definite presentation of the current state of biohydrogen production. Mechanisms of biohydrogen derived from APB are briefly summarized, including the transformation of light energy into adenosine triphosphate, the metabolism of organic matter producing hydrogen ions, and photosynthetic bacteria coupled with reducing substances. In addition, factors affecting biohydrogen production by APB, including internal factors and external factors, are systematically described and discussed. Moreover, current methods for improving the hydrogen production efficiency from APB are presented. Promising applications ingratiating sustainable development goals are summarized, and both economic viability and environmental sustainability are reviewed. [Display omitted] • Anoxygenic photosynthetic bacteria (APB) do not evolve O 2 in hydrogen production. • APB consume organic substrates and produce hydrogen at high rates. • ATP serving as co-factor participate in nitrogenase-catalyzed hydrogen evolution. • APB can yield carotenoid as by-products during the process of hydrogen production. • More high-quality life cycle assessment studies should be performed in the future. [ABSTRACT FROM AUTHOR]