Structure, functionality and bioactivity of sulfated polysaccharide extracted from rainbow trout byproducts: pH-shift method vs enzymatic hydrolysis.

Here, a novel method for sequentially extracting sulfated polysaccharides (SPs) from Oncorhynchus mykiss byproducts using alkaline/acid solubilization followed by isoelectric precipitation is compared with conventional enzymatic hydrolysis. Alkaline solubilization (SP-Alk) yielded SPs (2.46 %) comparable to the enzymatic method (SP-Enz, 2.77 %), while acidic solubilization (SP-Aci) yielded 1.96 %. SP-Alk showed comparable carbohydrate and sulfate content but lower protein than SP-Enz. Additionally, SP-Alk showed the highest monosaccharide content of rhamnose, mannose, glucose, and galactose. The extraction method affected the Molecular weight of SPs with SP-Enz having the lowest (44.95 kDa). Structural and thermal properties of the SPs were similar as revealed by FTIR/XRD and DSC, respectively. While SP-Enz exhibited slightly better antioxidant and functional properties (foaming, stability, emulsifying activity), SP-Alk showed a considerable performance with similar antimicrobial activity. Altogether, the pH-shift method can be a promising alternative for sequential extraction of SPs compared with enzymatic hydrolysis, avoiding enzymatic degradation of proteins.