EFFECT OF REACTION TIME AND SODIUM HYDROXIDE CONCENTRATION ON DELIGNIFICATION AND ENZYMATIC HYDROLYSISOF BREWER’S SPENT GRAIN FROM WO BRAZILIAN BREWERS

Abstract

Brazil, being one of the main beer producers, generates brewer’s spent grain as a main by-product of this industry, which is mainly composed of cellulose, hemicelluloses, lignin and extractives. The alkaline pretreatment of brewer’s spent grain received from two breweries is studied in this work, namely breweries Imperial (B1) and Colombina (B2). Factorial design (22) was realized with three experiments at the central point: contact time (30, 60, 90 min) and NaOH concentration (4%, 6%, 8%). It was found that the presence of extractives causes interference in the characterization of the material. The delignification process allowed obtaining materials with lower lignin percentages when higher NaOH concentrations were used, reaching percentages of lignin loss with values between 85-95%, in both materials, but for these conditions, the losses of cellulose were considerable – of 35-43%. Enzymatic hydrolysis of the pretreated materials achieved conversions greater than 70%, emphasizing that the greatest conversions were obtained with material B1, where almost the whole cellulose was hydrolyzed.