Gibberellic Acids Promotes Growth and Exopolysaccharides Production in Tetraselmis Suecica Under Reciprocal Nitrogen Concentration: An Assessment on Antioxidant Properties and Nutrients Removal Efficacy of Immobilized Iron-magnetic Nanoparticles

Abstract

The present study was aimed to assess the effect of gibberellic acids to enhance the growth, biomass, pigment, and exopolysaccharides production in Tetraselmis suecica under reciprocal nitrogen concentrations. For this study, the seven types of experimental media (N-P, NL-P/2GA3, N0-P/2GA3, NL-P/4GA3, N0-P/4GA3, NL-P/6GA3, N0-P/6GA3) were prepared include the addition of gibberellic acids under various nitrogen concentrations. The experiment was lasted for 15 days and the cell density, biomass, chlorophyll ‘a’, and exopolysaccharides (EPS) concentration of T. suecica were estimated for every three days. Then the EPS was subjected to the analyses of chemical (carbohydrate, protein, sulfate, and uronic acid), and antioxidant activity. In addition nutrient removal efficiency was evaluated by using different concentration of EPS. The highest DPPH (86.7±0.95 %) and hydroxyl radical activity (85.7±2.48 %) were observed in 2.5 and 1.2 mg/mL of EPS concentration. The immobilized magnetic Fe3O4-EPS nanoparticles (5.0 and 10.0 g/L) have efficiently removed the excessive phosphate (89.5±1.65 %) and nitrate (73.5±1.72 %) from the Litopenaeus vannamei cultured wastewater. Thus, applying gibberellic acids combined with limited nitrogen concentration could produce higher EPS that could exhibit excellent antioxidant activity, and nutrient removal efficacy in the form of Fe3O4-EPS magnetic nanoparticles.