Optimization of Alginate Extraction From Dictyota Mertensii From a Central Composite Design Associated With Response Surface Methodology: Characterization and Antioxidant Potential

Abstract This paper extracts alginate of Dictyota mertensii (DM), brown macroalgae found on the north coast of northeastern Brazil. A Composite Central Design (CCD) associated with Response Surface Methodology (RSM) was employed to optimize the extraction process of different fractions of alginate, in different conditions of time, temperature, and concentration of Na2CO3. Yield (𝜂), sulfate content, intrinsic viscosity ([𝜂]), viscosimetric molar mass (Mv), color parameters (a*, b* e L*), and M/G ratio are model response variables. The DM algae has its chemical composition expressed. Response surfaces are plotted from the variables studied, quadratic models were predicted, the influence of factors is analyzed, and response variables are subjected to analysis of variance (ANOVA) and F-test at 95% confidence. The antioxidant potential was evaluated based on the scavenging of the stable free radical 1,1-diphenyl-2-picrylhydrazyl (DPPH). The maximum extraction yield was 29.28±0.02 %, and sulfate content ranged from 3.50±0,00 % to 12.33±0.29 %. The maximum values of [𝜂] and Mv were 5.84±0.06 dL.g-1 and 278.00±2.66 kDa, respectively. The alginate showed a dark brown color and M/G ratio <1, indicating that the extracted alginate provides rigid and compact gels. The antioxidant potential and the CI50 were 54.93±0.27% and 0.51±0.07 mg.mL-1 , respectively, indicating moderate antioxidant activity.