Biophotolysis as a Sustainable Tool for Biohydrogen Production: A Systematic Review

Biophotolysis has emerged as a promising biotechnological alternative for the sustainable production of hydrogen, owing to the photosynthetic capacity of microalgae to convert solar energy into reducing equivalents under controlled conditions. This systematic review analyzed literature published between 2019 and 2024 in Science Direct, Scopus, and ResearchGate, with the objective of identifying the operational parameters, microorganisms, reactor configurations, and technological advances that determine process performance. Specific keywords and Boolean operators were applied to ensure a rigorous selection of recent studies. The findings indicate that Chlamydomonas reinhardtii is the most widely studied species, achieving hydrogen yields of up to 14.5 mL/L·h under optimized conditions such as sulfur deprivation, pH values between 7.0 and 7.5, moderate light intensities (100–200 μmol·m⁻²·s⁻¹), and enriched media such as TAP. Batch-type reactors demonstrated the highest efficiencies due to improved control of oxygen accumulation and light distribution, whereas tubular systems showed comparatively lower performance. This also reinforces the potential of biophotolysis for integrated bioremediation applications. Overall, biophotolysis represents a promising pathway for green hydrogen generation; however, its scalability requires further innovation in photobioreactor design, enzyme stability, and strategies to mitigate oxygen inhibition.