In this study, brewer's spent grain (BSG) was subjected to a range pretreatments to study the effect on reducing sugar yield. Glucose and xylose were found to be the predominant sugars in BSG. Brewers spent grain was high in cellulose (19.21 g/100 g of BSG) and lignin content (30.84 g/100 g of BSG). Microwave assisted alkali (MAA) pretreatment was found to be the most effective pretreatment for BSG, where the pretreatment was conducted at 400 W for 60 s. A maximum reducing yield was observed with high biomass loading (1 g/10 ml), cellulase (158.76 mu l/10 ml), hemicellulase (153.3 mu l/10 ml), pH (5.4) and an incubation time (120 h). Upon enzymatic hydrolysis, MAA pretreated BSG yielded 228.25 mg of reducing sugar/g of BSG which was 2.86-fold higher compared to native BSG (79.67 mg/g of BSG); simultaneously BSG was de-lignified significantly. The changes in functional groups, crystallinity and thermal behaviour was studies by means of FTIR, XRD and DSC, respectively. (C) 2017 Elsevier Ltd. All rights reserved.