Enzymatic Solubilization of Proteins in Brewer’s Spent Grain

Abstract

Brewer's spent grain (BSG) is an abundant, protein-rich coproduct from the beer industry. There is a growing interest in increasing and diversifying the exploitation of BSG and related coproducts for economic and environmental reasons. In this paper, we report on a study of the solubilization of proteinaceous material from BSG using several commercial peptidase preparations. Our data show that Alcalase is the most effective peptidase for solubilization of BSG proteins, with an ability to release up to 77% of total protein. The peptides produced by Alcalase had lower average molecular weight than peptides produced by the less effective enzymes. Processes that combined peptidase treatment with carbohydrate-degrading enzyme preparations such as Depol740 increased the solubilization of dry matter (from 30 to 43% under optimal conditions). However, such additional treatment had little effect on the solubilization of protein. The choice of enzyme dosage depends on the desired hydrolysis time and was assessed through several experiments. Protein solubilization was consistently better at pH 8.0 as compared to pH 6.8. Maximum protein solubilization at pH 8.0 within 4 h required the use of 10-20 microL Alcalase per g of dry matter. However, a considerable degree of solubilization (64%) and hydrolysates with high protein content could be obtained using doses down to only 1.2 microL. Amino acid composition analyses showed that Alcalase treatment solubilizes proline and glutamine (constituents of barley hordein) slightly more efficiently than the other amino acids in BSG.

Improvement of functional and antimicrobial properties of brewery byproduct hydrolysed enzymatically

“…Finally, at 24 h hydrolysis time, the DH was 21.80 AE 2.32%. Similar DHs were obtained by Treimo, Aspmo, Eijsinkm, and Hornm (2008). Contrarily, this DH value was higher that the previously value achieved with BSG hydrolysates by Celus, Brijs, and Delucour (2009), who hydrolysed a chemically isolated protein concentrate.…”

Brewers' spent grain: a review with an emphasis on food and health

“…However, an earlier study by this group demonstrated that inhibition of proteolytic activity in an enzyme preparation that had both carbohydrase and protease activities (Depol 740) only resulted in a 5% decrease in BSG solubilisation, suggesting that proteolytic activity is not essential (32). It was shown that 77% of the proteinaceous material in BSG could be solubilised with Alcalase, using a simple enzymatic hydrolysis step (34). Alcalase (protease from Bacillus licheniformis, Novozymes A/S) has been shown to be a very effective protease for solubilisation of BSG proteins.…”

Hydrolysis of Brewers' Spent Grain by Carbohydrate Degrading Enzymes

“…Feruloyl esterase activity has been measured in faecal samples 30 and in commensal bacteria 14,51 . The protein content of the hydrolysis residue could be minimized by combining an efficient protease to the process 50 . The lignin type residue could be used for an energy source or the properties of the lignin type material could be exploited in other applications.…”

“…Enzymatic hydrolysis is a potential method to solubilise BSG components for further fractionation due to the specificity and mild reaction conditions needed. Enzymatic hydrolysis of BSG has been investigated in order to solubilise proteins by proteolytic enzymes 13,32,50 , xylooligosaccharides by xylanases 28 , glucose by a mixture of hydrolases 37 or FA with feruloyl esterase either alone or together with xylanase 5,18 . Trichoderma enzymes have also been used to increase the amount of soluble dietary fibre in BSG 39 .…”