High Yield Protein Extraction from Brewer's Spent Grain with Novel Carboxylate Salt - Urea Aqueous Deep Eutectic Solvents

The sustainability of the global protein production is seriously challenged, why upgrading protein from new or under-utilized sources such as brewer's spent grain (BSG) is desirable. In this article a new method for high-yield protein extraction from BSG with deep eutectic solvents (DESs) is reported. Novel carboxylate salt - urea DESs are described and protein extraction from BSG using 6 of these mixtures is compared. The extraction with 90 wt% NaAcO : urea (molar ratio 1:2) was compared to choline chloride : urea (1:2), of which the first was found to be a more suitable protein extractant with up to 79% extraction yields from BSG. Based on microscopy, it is proposed that the high extraction yield from BSG with 90wt% NaAcO : urea (1:2) was due to dissolution of proteins insoluble by nature or denatured during the brewing process. The production of protein concentrates with a protein content of > 50wt% was demonstrated and the fractions were characterized in detail.