Process Intensification of Pigment Extraction from Microalgae: A Close Look at Scale-Up, Sustainability and Economy of the Processes

Microalgae is an important bioresource for a wide range of valuable bioactive compounds such as pigments, proteins, fatty acids and polysaccharides. Among these various potential products that may be obtained from microalgae, pigments such as phycocyanin, phycoerythrin, beta-carotene, astaxanthin, xanthophylls, fucoxanthin, lutein, chlorophyll, offer immense potential. These natural pigments are used in pharmaceuticals, nutraceuticals, food and cosmetic industries. Extraction of pigments from microalgae involves various process steps that include harvesting of microalgal biomass, disruption of the cell wall, separation of cell debris and purification of the desired pigment. Several alternative methods and processes have been proposed for extracting pigments from microalgae. There is a significant scope to intensify these processes for improving pigment recovery with significant techno-economic benefits. However, it must be noted that these pigments are often thermolabile and process intensification may adversely influence their structure, stability and physiological properties which may jeopardise their commercial value. In this chapter, we have critically reviewed the process intensification of pigment recovery (extraction and purification) from microalgae with a focus on efficiency and sustainability. The state-of-the-art key processes such as aqueous two-phase extraction, membrane processing, adsorption etc. used for extracting bioactives and pigments are reviewed. Recent developments in process intensification using hydrodynamic cavitation, ultrasonication, microwave-assisted extraction, pulsed electric field (PEF) assisted extraction, pressurised liquid extraction, supercritical fluid extraction and other intensification methods are thoroughly discussed. A discussion on techno-economic aspects and scale-up for potential translation to commercial practice is included. We hope that the discussion will stimulate further research and commercial exploitation of pigments and bioactives recovery from microalgae.