Brewers' spent grain: generation, characteristics and potential applications

Brewers' spent grain (BSG) is the major by-product of the brewing industry, representing around 85% of the total by-products generated. BSG is a lignocellulosic material containing about 17% cellulose, 28% non-cellulosic polysaccharides, chiefly arabinoxylans, and 28% lignin. BSG is available in large quantities throughout the year, but its main application has been limited to animal feeding. Nevertheless, due to its high content of protein and fibre (around 20 and 70% dry basis, respectively), it can also serve as an attractive adjunct in human nutrition. Recently, attempts have been made to use BSG in biotechnological processes, such as in cultivation of mushrooms and actinobacteria, as a source of value-added products, such as, ferulic and p-coumaric acids, xylose, arabinose, or as raw material for xylitol and arabitol production. The main characteristics and potential applications of BSG are reviewed focussing on these alternative uses of this agro-industrial by-product as a raw material in foods, in energy production and in biotechnological processes.