Effects of protease and protease dose applied in protein extraction on nutritional value of brewer's spent grain residue

The study was conducted to evaluate the effects of enzyme and enzyme dose applied in protein extraction of brewer's spent grains (BSG) on nutrient content and in vitro digestibility of dry matter (DMD) and NDF (NDFD) of BSG residue. The experiment was a 2x4 + 1 factorial arrangement including protease (alcalase, everlase) and enzyme doses (Low, Med, MedH and High, respectively as 1:100, 5:100, 10:100, 15:100; w/w) plus BSG. Substrates were incubated for 24 h in batch culture. The protein extraction process increased the content of neutral detergent fibre (NDF) and decreased crude protein (CP) content of BSG residue. Enzyme x enzyme dose was noticed for DMD. The DMD was greater at Low dose, but it was lower at MedH dose with alcalase than with everlase. Increasing alcalase dose linearly decreased DMD and volatile fatty acid (VFA) concentration. However, the DMD and VFA concentration linearly increased with increasing everlase dose. Compared with BSG, the DMD and VFA concentration of residues decreased, whereas NDFD improved.