Enzyme-assisted extraction of carbohydrates from the brown alga Ecklonia radiata: effect of enzyme type, pH and buffer on sugar yield and molecular weight profiles

Abstract

The aim of this study was to understand the carbohydrate yield, composition, and molecular weight (MW) profiles of extracts from the brown alga Ecklonia radiata prepared using an enzyme-assisted extraction approach. The most significant effect on the total sugar yield was observed when comparing the use of salt-containing buffers (7.9–23.9 g × 100 g−1 dry weight (DW)) to pH-adjusted water (23.6–27.9 g × 100 g−1 DW), with the buffers significantly reducing the extraction efficiency in all instances. The inclusion of selected enzymes had little or no impact on total sugar yield, when compared with the corresponding solvent or buffer-only extractions. Marginal differences on total sugar yield were found when using different carbohydrate hydrolytic enzymes and proteases, and when changing pH in pH-adjusted water extractions. Both enzymes and pH influence sugar composition, and significantly affect MW profile of the polysaccharide fractions but in different ways. The acidic extraction at pH 4.5 yields lower MW components. Enzyme-assisted extraction reduced the MW of the extracted polysaccharides by 20–50% compared to pH-adjusted water only extractions.