Extraction and purification of seaweed protein from Ulva sp. - Challenges to overcome

Abstract

Ulva sp. has gained attention as a promising and sustainable protein source, due to its high essential amino acid content. This study investigated traditional extraction methods using a double screw press followed by acid or heat precipitation. Furthermore, the screw pressing was combined by a novel purification method that combines mild heat treatment with microfiltration for removal of chlorophyll, to produce white Ulva protein. The double screw press followed by acid precipitation or heat denaturation showed low total protein yields, with 14% of the biomass protein extracted, of which half was soluble. The highest total protein yield (5.5%) was achieved with acid precipitation at pH 2, while heat denaturation at 90 °C resulted in a total protein yield of 4.1%. Acid precipitation proved to be effective with ∼ 81% precipitation of solubilized protein compared to ∼ 43% for heat denaturation. While microfiltration effectively retained chlorophyll in the retentate, the recovery of protein in the permeate remained challenging. SDS-PAGE analysis of proteins in different microfiltration-fractions showed that larger protein complexes (>250 kDa) were unable to transmit through the membranes, resulting in a maximum recovery of 24.9% of the feed-protein in the permeate. Further refinement of Ulva fractionation protocols is imperative for improvement.