Background: Brewers’ spent grain (BSG) contains 20 ~ 29% protein with high amount of glutamine, proline and hydrophobic and non-polar amino acid residues, making it an ideal material for producing value-added products like bioactive peptides. Protein were extracted from BSG, hydrolyzed with 1% alcalase and flavourzyme, and the generated protein hydrolysates (AlcH and FlaH) showed antioxidant activities. This study was conducted to evaluate effects of AlcH and FlaH on gas production, fermentation characteristics, nutrient disappearance, microbial protein synthesis and microbial community using an artificial rumen system (RUSITEC) fed a high-grain diet.Results: Supplementation of FlaH decreased (P < 0.01) disappearances of dry matter (DM), organic matter (OM), crude protein (CP) and starch, without affecting fibre disappearances; while AlcH had no effect on nutrient disappearance. Neither AlcH nor FlaH affected gas production and VFA profiles, except they enhanced (P < 0.01) NH3-N but decreased (P < 0.01) H2 production. Supplementation of FlaH decreased (P < 0.01) percentage of CH4 in total gas and dCH4 in dissolved gas. Addition of monensin reduced (P < 0.01) nutrient disappearances, improved fermentation efficiency and reduced CH4 and H2 emission. Total microbial nitrogen production decreased (P < 0.05) but proportion of feed particle associated (FPA) bacteria increased with FlaH and monensin. Numbers of OTUs or Shannon diversity indices of FPA microbial community were unaffected by AlcH and FlaH; whereas both indices were reduced (P < 0.05) by monensin. Taxonomic analysis revealed no effect of AlcH and FlaH on the relative abundance (RA) of bacteria at phylum level; monensin reduced (P < 0.05) the RA of Firmicutes and Bacteroidetes and enhanced Proteobacteria. The FlaH enhanced (P < 0.05) the RA of genus Prevotella, reduced Selenomonas, Shuttleworthia, Bifidobacterium and Dialister as compared to control; monensin reduced (P < 0.05) RA of genus Prevotella but enhaced Succinivibrio.Conclusions: Inclusion of FlaH in high-grain diet may potentially protect CP and starch from ruminally degradation, without adversely affecting fibre degradation and VFA profiles. The FlaH also showed promising effects on reducing CH4 production by suppressing H2 generation. Protein enzymatic hydrolysates from BSG using flavourzyme showed potential application to high value-added bio-products.

Background Brewers’ spent grain (BSG) typically contains 20 ~ 29% crude protein (CP) with high concentrations of glutamine, proline and hydrophobic and non-polar amino acid, making it an ideal material for producing value-added products like bioactive peptides which have antioxidant properties. For this study, protein was extracted from BSG, hydrolyzed with 1% alcalase and flavourzyme, with the generated protein hydrolysates (AlcH and FlaH) showing antioxidant activities. This study evaluated the effects of AlcH and FlaH on gas production, ruminal fermentation characteristics, nutrient disappearance, microbial protein synthesis and microbial community using an artificial rumen system (RUSITEC) fed a high-grain diet. Results As compared to the control of grain only, supplementation of FlaH decreased ( P < 0.01) disappearances of dry matter (DM), organic matter (OM), CP and starch, without affecting fibre disappearances; while AlcH had no effect on nutrient disappearance. Neither AlcH nor FlaH affected gas production or VFA profiles, however they increased ( P < 0.01) NH 3 -N and decreased ( P < 0.01) H 2 production. Supplementation of FlaH decreased ( P < 0.01) the percentage of CH 4 in total gas and dissolved-CH 4 (dCH 4 ) in dissolved gas. Addition of monensin reduced ( P < 0.01) disappearance of nutrients, improved fermentation efficiency and reduced CH 4 and H 2 emissions. Total microbial nitrogen production was decreased ( P < 0.05) but the proportion of feed particle associated (FPA) bacteria was increased with FlaH and monensin supplementation. Numbers of OTUs and Shannon diversity indices of FPA microbial community were unaffected by AlcH and FlaH; whereas both indices were reduced ( P < 0.05) by monensin. Taxonomic analysis revealed no effect of AlcH and FlaH on the relative abundance (RA) of bacteria at phylum level, whereas monensin reduced ( P < 0.05) the RA of Firmicutes and Bacteroidetes and enhanced Proteobacteria. Supplementation of FlaH enhanced ( P < 0.05) the RA of genus Prevotella , reduced Selenomonas , Shuttleworthia , Bifidobacterium and Dialister as compared to control; monensin reduced ( P < 0.05) RA of genus Prevotella but enhaced Succinivibrio . Conclusions The supplementation of FlaH in high-grain diets may potentially protect CP and starch from ruminal degradation, without adversely affecting fibre degradation and VFA profiles. It also showed promising effects on reducing CH 4 production by suppressing H 2 production. Protein enzymatic hydrolysates from BSG using flavourzyme showed potential application to high value-added bio-products.