Priority-based multiple products from microalgae: review on techniques and strategies

Microalgal biomass is composed of different valuable metabolites that can satisfy the requirements of renewable biofuels, alternative proteins, carbohydrates, and food grade natural colorants. Production of a specific product from microalgae has been proved to be economically infeasible on the commercial scale except for the production of high-value products (e.g. carotenoids and phycobiliproteins). Therefore, the simultaneous extraction of multiple products is essential to bring pragmatism for the production of biofuels, proteins, and carbohydrate derived products from microalgal biomass. In order to obtain multiple products, various strategies have been implemented using potential techniques of cell disruption and biomass fractionation based on the priorities of products. Conventional approaches of downstream processing have often proved to be inefficient in the case of integrated fractionation systems. This is attributable to the divergent nature of the intracellular metabolites of microalgae and their vulnerability toward the different chemicals and conditions of those downstream processes. However, three phase partitioning (TPP), aqueous two-phase separation, membrane separation, supercritical fluid extraction (SFE), and pressurized liquid extraction (PLE) are some of the advanced techniques which have been proved to be useful in this regard. Choice of cell disruption mechanisms is critical for several purposes, such as the selective release of metabolites into a suitable solvent, preservation of bioactivity of molecules and cost-savings. Unfortunately, consolidated report for the fractionation of priority-based products from microalgal biomass using these techniques is lacking. Therefore, in this review, we have critically discussed the different strategies for the priority-based multiple products by implementation of the advanced techniques.