Extraction and characterization of protein from Irish brown seaweed Ascophyllum nodosum

This study investigates traditional and non-conventional methods of extraction of protein from Irish brown seaweed A. nodosum. Acid, alkali, combined acid-alkali with and without ultrasound pretreatment were investigated for extraction of protein from A. nodosum. Molecular weight of protein was determined using high performance size exclusion chromatography and amino acid profiling was carried out using an amino acid analyzer. Combination of first acid and then alkali extraction was found to be the most efficient method of extraction among all methods investigated (59% of recovery); followed by single step of alkali extraction assisted with ultrasound (68.4μm) which was able to extract 57% of total protein. Alkaline extraction was shown to yield the best protein/algae liquefaction ratio (1.28). This can be attributed to the release of polysaccharide complexes first by acid and then solubilization of proteins by alkali solvent. The molecular weight of extracted protein was found to be relatively low, in the range of 2-4kDa average MW. The alkali method of extraction was found to be optimum for extraction of amino acids from A. nodosum.