Microalgae-bacteria consortium for biohydrogen production ‐ A potential microbial catalyst? A review on mechanism, influencing factors and process optimization

The global energy demand is increasing, and most of the energy supply mainly depends on fossil fuels, significantly contributing to global warming. It necessitates finding alternate energy sources to overcome the adverse impacts of fossil fuels. Hydrogen is a prominent fuel due to its higher energy density than other fossil fuels and zero carbon emissions. Hydrogen production from third-generation biofuel microalgae (Biohydrogen) is considered an environmentally friendly and cost-effective method because it does not require more energy and does not produce any toxic intermediates. Moreover, microalgae require only essential nutrients like nitrogen and phosphorous and sunlight to produce biohydrogen. The wastewater from domestic and selected industries is an excellent medium for biohydrogen production, and the potential of microalgae to treat wastewater is an additional benefit to microalgae-based biohydrogen production. However, the main obstacles hindering the widespread growth of microalgae are the high harvesting cost of biomass, low biomass production, treatment efficiency, and low hydrogen yield. This review mainly focuses on the potential of the microalgae-bacterium consortium in biohydrogen production to enhance the yield. The various microalgae species and bacteria for biohydrogen production and their characteristics, synthesis, and mechanism of biohydrogen production are presented. In addition, the possibility of utilizing wastewater as a substrate, various influencing factors and limitations in the approach of microalgae-bacteria consortium, and the future directions in improving the biohydrogen production potential are discussed.