Microwave-assisted extraction of sodium alginate from brown macroalgae Nizimuddinia zanardini, optimization and physicochemical properties

In this study, sodium alginate was isolated from Nizimuddinia zanardini by microwave-assisted extraction method. A Box-Behnken design (BBD) was applied to study the effect of temperature (45-75 degrees C), time (10-30 min), microwave power (300-500 W), and solvent/ biomass ratio (10-30 mL/g) on the extraction yield (EY) and uronic acid content (UA) of sodium alginate. The extracted sodium alginate was assessed for its chemical compositions, antioxidant activity, emulsifying index, and intrinsic viscosity. EY at optimal conditions (temperature of 67 degrees C, microwave power of 400 W, and solvent/biomass ratio of 29 mL/g after 19 min) was 31.39% (w/w). The protein, carbohydrate, total phenolic, and UA content of sodium alginate obtained at optimal conditions were about 1.00, 73.30, 1.62, and 62.33%, respectively. The emulsifying index (E-24) of sodium alginate extracted by microwave (SA-MW) with sunflower oil (64.41%) and olive oil (67.25%) was higher than sodium alginate extracted by the conventional method (SA-CN) (55.00% and 58.49%, respectively).