Phycoprospecting the nutraceutical potential of Isochrysis sp as a source of aquafeed and other high-value products

Marine microalgae, an exceptionally diverse yet highly specialized group of photoautotrophs are the key regulators of ecological habitats and aquatic ecosystems. Isochrysis, a ubiquitously present golden-brown flagellate, isolated from southern coastline of India, was assessed as a suitable feed source for aquaculture. Absence of tough cell walls with an appropriate ingestible cell size of 4-5 mu m and fast growth rate besides possessing essential nutritive constituents like high per cent of cellular lipids (32% dry weight [DW]) and significant yield of eicosapentaenoic acid (EPA) (10.21 mg g(-1) DW) and docosahexaenoic acid (DHA) (7.24 mg g(-1) DW) proves this strain as an ideal option for aqua feed. The concomitant synthesis of carotenoids and numerous secondary metabolites also highlighted its incomparable antioxidant capacity (up to 43.4% inhibition of alpha, alpha-diphenyl -beta-picryl hydrazyl (DPPH) radical) as well as their role as a biocontrol agent in preventing growth of fish pathogens like Aeromonas. This study thereby demonstrates the potential utilization of Isochrysis as a quintessential dietary supplement, and fish feed as a sustainable feedstock.