Light-dependent biohydrogen production: Progress and perspectives

The fourth industrial revolution anticipates energy to be sustainable, renewable and green. Hydrogen (H2) is one of the green forms of energy and is deemed a possible solution to climate change. Light-dependent H2 production is a promising method derived from nature's most copious resources: solar energy, water and biomass. Reduced environmental impacts, absorption of carbon dioxide, relative efficiency, and cost economics made it an eyecatching approach. However, low light conversion efficiency, limited ability to utilize complex carbohydrates, and the O2 sensitivity of enzymes result in low yield. Isolation of efficient H2 producers, development of microbial consortia having a synergistic impact, genetically improved strains, regulating bidirectional hydrogenase activity, physiological parameters, immobilization, novel photobioreactors, and additive strategies are summarized for their possibilities to augment the processes of bio-photolysis and photo-fermentation. The challenges and future perspectives have been addressed to explore a sustainable way forward in a bio-refinery approach.