Advancements in direct bio-photolysis: optimizing photosynthetic hydrogen production through environmental and genetic innovations

Direct bio-photolysis, which harnesses the photosynthetic capabilities of cyanobacteria and green algae to split water into hydrogen and oxygen using sunlight, represents a promising route toward sustainable hydrogen production. Unlike previous reviews that treat these enhancement approaches separately, this paper uniquely integrates environmental, genetic, and nanomaterial-based strategies into a unified comparative framework. The review critically evaluates recent progress in optimizing environmental conditions; such as nutrient limitation, light intensity, and temperature regulation alongside advances in genetic engineering, including the development of oxygen-tolerant hydrogenases, temperature-sensitive mutants, and metabolic pathway rewiring to enhance electron transfer. Furthermore, it examines the incorporation of nanomaterials such as quantum dots, metal–organic frameworks, and protein-encapsulated nanoparticles, which have improved light absorption, charge transfer, and enzyme stability. This integrative analysis reveals systematic trade-offs between catalytic efficiency, enzyme stability, and system scalability, emphasizing that true performance gains arise from the synergy of molecular, material, and environmental design. The paper concludes by outlining future directions for scalable, industrial-level bio-photolysis through modular bioreactor design, synthetic-biology-driven control systems, and interdisciplinary collaboration. Collectively, this review establishes a systems-level framework for transforming direct bio-photolysis from laboratory research into a viable, carbon-neutral technology for clean hydrogen production.