A review on pretreatment methods, photobioreactor design and metabolic engineering approaches of algal biomass for enhanced biohydrogen production

The development of alternative fuels has been promoted by the extreme fossil fuel consumption brought on by urbanisation and deteriorating pollution. Due to its high energy and combustible qualities, biohydrogen has been perceived as a potential fuel substitute in dealing with issues related to the rising emission of greenhouse gases and global warming. As a source of carbon sequestration and sustainable renewable energy, biohydrogen synthesis by algae species has been prevalent in research scale. This review focuses on the novel and recent metabolic approaches for enhanced algal based biohydrogen production. Pretreatment methods available and scaling techniques used for enhancing the biohydrogen productivity using algal species have been elaborated in the review. Algal characteristics that make them suitable alternative for biohydrogen production are discussed briefly. Various pretreatment methods such as physical, chemical, biological and thermal are elaborated. In addition, the factors involved in influencing the biohydrogen productivity and the metabolic engineering approaches for modifying the pathway in algae are highlighted. Scaling up of process using different types of photobioreactors such as tubular, flat panel, airlift and stirred tank are reported that briefs about merits and demerits of each photobioreactor.