Biophysical-chemistry Characterization of Alginate in Brown Algae Species Sargassum dupplicatum

Alginate is a high-value biopolymer, exists in brown algae, and applied widely in numerous fields, for example, food, functional foods, and pharmaceutics. The study focused on the biophysical-chemistry characterization of alginate in brown algae species Sargassum dupplicatum grown commonly in Vietnam under the effect of NaCl, KCl, MgCl2, chitosan, carrageenan, and ethanol in different physical condition. Antioxidant activity of alginate and their compound was also studied. The results showed that Na_Alg, K_Alg, and Mg_Alg disperse the net style in the water. Ca_Alg, chitosan_Alg, and Carrageenan_Alg absorbed water and swelled for forming a sphere, yarn, and yarn in the water, respectively. Chitosan_Alg and carrageenan_Alg precipitated faster in ethanol, compared to Na_Alg, K_Alg, and Mg_Alg. 20% of ethanol did not cause the precipitation of Alginate salt, Chitosan_Alg, and carrageenan_Alg for 30 minutes. Alginate salt, Chitosan_Alg, and Carrageenan_Alg were full precipitated for 30 minutes when using ethanol concentration was more than 80%. Chitosan_Alg and Carrageenan_Alg occurred the precipitation in 20% of ethanol for 30 minutes. Total antioxidant activity and reducing power activity of chitosan_Alg got the highest value (a and b, respectively), compared to Carrageenan_Alg, Na_Alg, K_Alg, and Mg_Alg. The antioxidant activity difference in a group of Na_Alg, K_Alg, and Mg_Alg, and a group (Chitosan_Alg and Carrageenan_Alg) did not happen. The difference only occurred between the two groups.