Recent advances in microalgae-based biohydrogen production: A review of innovative strategies, pretreatment, genetic engineering, and bioelectrochemical technologies

Abstract

Microalgae are promising platforms for sustainable biohydrogen (H2) production, which couples both the production of H2 and CO2 sequestration and wastewater treatment. Limiting oxygen sensitivity of [FeFe]-hydrogenases and the limitations of reactors are the main implementation issues. This review discusses advances in the biohydrogen production from green microalgae and cyanobacteria. We discuss the photobiological H2 pathway, dark fermentative H2 from algal biomass and bioelectrochemical H2-hybrids. Process strategy involving nutrient-starvation methods, algae and bacteria consortia as well as photobiorector designs, is analyzed for better H2 yield. We review pretreatment approaches, i.e., mechanical, thermal, chemical, enzymatic, and bio-nanoparticle approaches that increase fermentative hydrogen production by solubilising solids. Genetic engineering advances are also featured, which include hydrogenase engineering, pathway modifications, and starch accumulation in species. We discuss some bio-electrochemical systems with a particular focus on the microalgae integration and microbial electrodelysis cells coupled with photosynthesis for hydrogen evolution. Pilot demonstrations are evaluated, where research priorities are genetic modifications, biorefinery concepts, reactor engineering and techno-economic analysis.