Recovery and Bioactivities of Pacific Dulse Protein and Its Hydrolysates

Abstract

Abstract Objectives Pacific dulse (Palmaria mollis) is a protein-rich red algae cultivated in the Pacific Northwest, originally as aquaculture feed and now expanding to human consumption. Our previous work showed that the dietary supplementation of dulse exerts anti-inflammatory effects in vivo using an obese murine model. This study aims to optimize dulse protein recovery and asses their bioactivities that may be associated to the earlier observation. Methods Fresh dulse samples were washed, freeze-dried and milled into powder. Effect of extraction ratio, cellulolytic enzyme addition and extractant type on protein recovery was assessed. Osborne method was employed to recover protein fractions soluble in aqueous, saline (3.5% NaCl), alkaline (0.12N NaOH) and alcoholic (70% ethanol) solutions. Dulse hydrolysates were prepared using five commercial proteases. Electrophoretic profiles were determined using SDS-PAGE. Anti-inflammatory activity of samples were tested against LPS-induced RAW 264.7 macrophages while antioxidant activity was assessed using ABTS radical scavenging assay. Results Extraction of Pacific dulse protein was optimal at 1:25 (wt/vol) extraction ratio. Use of 2% (vol/vol) cellulolytic enzymes enhanced the recovery by more than 2-folds. The use of Osborne method increased the protein yield as some salt-soluble and alcohol soluble proteins were also recovered. Aqueous soluble protein hydrolysates were non-cytotoxic and exerted significant anti-inflammatory activities in RAW 264.7 macrophages as evidenced by reduced LPS-induced nitrite production. Both aqueous and alkaline soluble protein and their respective hydrolysates achieved effective radical scavenging in vitro indicating antioxidant effects. Conclusions Our results suggest that dulse is a promising resource for bioactive proteins and peptides recovery. Further work is currently being conducted to confirm the observed bioactivities, identify active peptides, and elucidate mechanism of action. Funding Sources Oregon State University Agricultural Research Foundation.