Protease hydrolysed brewers’ spent grain bioactive extracts for applications in human health

Abstract

AbstractAbout 39 million tons of Brewer’s spent grain (BSG), the main by-product of beer manufacturing, are produced annually and is used for low value applications. To valorise this rich bioresource, the present work entails bioprocessing of BSG with various proteases (Novozymes) at two different concentrations (4% and 9%) to solubilise protein, carbohydrate and polyphenols from the grain and evaluate its effect on gut and brain health. The results show the highest (p < 0.05) FRAP (Ferric Reducing Antioxidant Power) based antioxidant activity was obtained for Pro 5 (4%: 108.10 ± 4.17 µmole Trolox Equivalence (TE)/g protein, 18.06 ± 0.70 µmole TE/g d.w., which was 3.6 times higher than untreated control extracts. The highest DPPH (1,1-diphenyl-2-picrylhydrazyl) scavenging activity was obtained for the same extract (Pro 5 at 4%: 0.118 ± 0.006 µg AAE/mg d.w., 9%: 0.110 ± 0.006 µg AAE/mg d.w). Proximate composition showed this extract to contain the highest concentration of proteins at 21.66% ± 2.71, and color analysis showed the same Pro 5 (4%) extract to be the darkest (L*53.73) indicating the possible presence of dark polyphenols. Anticancer screening showed Control and Pro 1 to possess cytotoxic effect against colon cancer cells with IC50 of 3.2 and 13.91 mg/mL, respectively. No significant activity was noted against the brain cancer cell line. Thus anti-colon cancer activity of BSG extracts highlights its potential in gut health. The observed bioactivity resulted from a combination of peptides, carbohydrates and polyphenolic compounds in the extract and warrants further characterisation for targeted nutraceutical applications. Graphical abstract