Marine microalgae as sustainable feedstock for multi-product biorefineries

Marine microalgae accumulate numerous compounds with commercial value including carotenoids, proteins, biopolymers, and lipids, making them attractive feedstocks to produce diverse bioproducts including pharma-ceuticals, nutraceuticals, cosmetics, animal feed, and biofuel. With the emerging concepts of "Blue Economy" and "Blue Biotechnology", marine microalgae can be employed to achieve sustainability in numerous industries. Nonetheless, microalgae-based production processes are still not considered economically feasible owing to the high costs associated with cultivation and biomass processing. To mitigate the costs associated with the pro-duction process, the concept of marine microalgae-based biorefining has emerged where a single feedstock is employed to produce several distinct bioproducts, each with commercial value. Marine microalgae-based bio-refineries could be made economically feasible by incorporating both high-value and low-value bio-compounds in the production line, whereas utilization of wastewater and flue gases as alternative nutrient sources for the cultivation can make the process more sustainable. Nonetheless, several challenges are associated with marine microalgae-based biorefinery, which necessitate the attention of future researchers to make this concept a reality. Hence, the present review provides a comprehensive discussion on the biorefinery of marine microalgae in view of producing diverse metabolites using a single feedstock while providing valuable insight into the directions of future research.