Study of extraction parameters, quantitative yield of polysaccharides and antioxidant activity of psychrophilic microalgae and cyanobacteria

Exopolysaccharides and endopolysaccharides are the main components in the antioxidant complex of psychrophilic microalgae and cyanobacteria. The extraction of these compounds from the cells is really energy consuming, as well as it requires large doses of chemicals due to the resilience, recalcitrance, complexity and diversity of the cell wall in microalgae. The purpose of this article was to study the dependence of polysaccharides quantitative yield on the power of ultrasound treatment and duration of their extraction, as well as to determine the antioxidant activity of the antioxidant complex of psychrophilic microalgae and cyanobacteria. In order to find and confirm the antioxidant properties of the complexes obtained from the microscopic algae biomass, we used the method based on measuring the optical density (in a liquid nutrient medium), i. e. the method for determining the antioxidant activity of the samples under research by their ability to reduce the level of free radicals. As a result of the studies the rational conditions were found for the extraction of the antioxidant complex from the cell culture fluid, and from the cell-related psychrophilic microalgae and cyanobacteria Skeletonema pseudocostatum, Thalassiosira pseudonana, Fragilariopsis kerguelensis, Aphanizomenon gracile, and Anabaena cylindrica. For the exopolysaccharides extraction from the psychrophilic microalgae and cyanobacteria Skeletonema pseudocostatum, Thalassiosira pseudonana, Fragilariopsis kerguelensis, Aphanizomenon gracile and Anabaena cylindrica, the method of ethanol extraction with an extraction module of 1:2 and an extraction temperature of 5 °С was used. The ability of psychrophilic microalgae and cyanobacteria Skeletonema pseudocostatum, Thalassiosira pseudonana, Fragilariopsis kerguelensis, Aphanizomenon gracile and Anabaena cylindrica to produce an antioxidant complex was studied. It was found that this complex contains polysaccharides: endopolysaccharides and exopolysaccharides in particular. The ability of psychrophilic microalgae and cyanobacteria Skeletonema pseudocostatum, Thalassiosira pseudonana, Fragilariopsis kerguelensis, Aphanizomenon gracile, and Anabaena cylindrica to produce an antioxidant complex was proven by the presence of significant antioxidant activity of psychrophilic microalgae and cyanobacteria, determined and confirmed by the methods ABTS, DPPH, and FRAP. The psychrophilic microalga Skeletonema pseudocostatum possesses the highest antioxidant activity. The availability of antioxidant properties in psychrophilic microalgae and cyanobacteria opens up the prospects for their practical application.