Reviewing biohydrogen production from microalgal cells through fundamental mechanisms, enzymes and factors that engendering new challenges and prospects

Hydrogen is the most promising alternative energy recently that is renewable and clean due to its sustainability, great potential as energy source and efficiency during the conversion. In fact, microalgal biohydrogen has attracted significant attentions as a clean and sustainable fuel to achieve the carbon neutrality and sustainability in environment. In this review, the mechanisms of biological methods and electrochemical methods, and the enzymes involved in the biohydrogen generation from microalgae have been inclusively and rudimentary detailed. The review also summarizes the benefits and drawbacks of each technique, and compares the biohydrogen yields from each method based on the results reported by the recent studies. Furthermore, the key factors that influence the biohydrogen yields including pH, light intensity, cell density, temperature and substrate introduced have been addressed as well in this review. Moreover, the review also highlights the primary shortcomings encountered which are oxygen sensitivity of enzymes and low biohydrogen yield. Lastly, the resolutions to enhance the biohydrogen production together with the future prospects for sustainable biohydrogen production from microalgae are opined systematically. © 2023 Elsevier Ltd