Photobiological Hydrogen Production by Photosynthetic Microorganisms: Integrating Microbial Systems and Bioprocess Engineering

Hydrogen (H2) is widely regarded as a critical energy vector for achieving carbon neutrality, owing to its high energy density and CO2-free combustion. Among sustainable production methods, photobiological H2 synthesis using photosynthetic microorganisms has emerged as a promising strategy due to its ability to directly convert light energy into chemical energy. These biological systems use enzymatic pathways such as hydrogenases and nitrogenases to produce H2 from water or organic substrates under moderate conditions. However, practical implementation remains limited by low solar-to-H2 conversion efficiencies, oxygen sensitivity of catalytic enzymes, and technical challenges in photobioreactor systems. This paper reviews the current state of photobiological H2 production, focusing on mechanistic challenges, photobioreactor design, substrate utilisation, and immobilisation techniques. Integrating biological and engineering approaches is expected to play a crucial role in advancing photobiological H2 production towards large-scale implementation.