Enzymic Hydrolysis of Brewers' Spent Grain

Enzyme hydrolytic products of brewers' spent grain (SG) have a representative composition of: 9.6% total lipid, 4.3% ash, 31% protein, 9% cellulose, 12% starch and β-glucans, 19% pentosans (xylose:arabinose: 12:7), and 16% lignin. Treatment of commercial dried, milled SG (CSG) with a crude cellulase preparation hydrolyzed all of the starch and β-glucans, about two-thirds of the cellulose and one-half of the pentosans into the constituent monosaccharides. The cellulase did not effectively hydrolyze the cellulose and pentosans in pilot wet, unmilled SG (PSG). In about 6 hr, a protease hydrolyzed up to 87% of the protein in CSG and PSG to soluble products, 85% of which had a molecular weight less than 3500. After treatment of the CSG with crude cellulase plus protease, about 53% was hydrolyzed to form soluble nutrients.