Millions of tonnes of brewer's spent grain (BSG) are annually produced worldwide as a by-product of the brewing industry. BSG has the potential to be a valuable source of food, chemicals and energy if cost-efficient fractionation methods can be developed. A 2-fold improvement in carbohydrate solubilisation could be achieved through the introduction of a milling step prior to enzymatic hydrolysis. Course and fine milled fractions were characterized by particle size distribution and light microscopy. Fine milling decreased particle size down to the micron level and this in turn improved the carbohydrate solubility yield by a multi-enzyme mixture from 23% up to 45%. Carbohydrate solubilisation could be further increased through the supplementation of this enzyme preparation with additional cellulases. The physical degradation caused by the milling also liberated soluble carbohydrates without the requirement of any enzymatic treatment. (C) 2012 Elsevier Ltd. All rights reserved.