Optimization of the culture medium and characterization of antioxidant compounds of a marine isolated microalga as a promising source in aquaculture feed

Abstract

Microalgae as photosynthetic microorganisms can be grown under controlled conditions that make them a potential source of highly valuable compounds utilized in aquaculture feed and different nutraceutical industries. The main objective of this research was to optimize the culture medium of Picochlorum sp. RCC486 as a new marine isolate for improving its growth in a microplate system using the Taguchi method. The methanol extract showed maximum FRAP activity with a value increased to 455.88 μM Fe 2+ at the concentration of 1 mg/mL. Also, the antioxidant activity of all 8 fractions purified from the methanolic extract by the TLC method was evaluated. The potent activity was observed for two fractions T1 and T2 with 544.68 μM Fe 2+ and 449.08 μM Fe 2+ at the concentration of 1 mg/mL. The GC-MS analysis was performed to identify various constituents of fractions with strong reducing power. The presence of Hexadecane: Dodecane (8.97%), and Tetradecane: Nonadecane (7.01%) in T1 fraction, and ((1,2-Benzenedicarboxylic acid, bis (2-methyl propyl) ester (12.37%), Dodecane (2.84%), Hexadecane (1.03%) and Decane: Undecane (0.74%)) in T2 fraction of methanol extract of Picochlorum sp. Contribute directly to the antioxidant effect that makes the microalga as a promising feedstock for future studies in aquaculture feed or nutraceutical industries. • KNO 3 and phosphate meaningfully affect the growth of isolated microalga. • The hexane extract showed the most DPPH and ABTS radical scavenging activity. • The methanol extract showed maximum FRAP activity and fractionated using TLC. • Identify various constituents of the more active fractions using GC-MS analysis. • Determing the compounds that contribute directly to the antioxidant effect.