Ultrasound Technology Applied to Enhance Enzymatic Hydrolysis of Brewer’s Spent Grain and its Potential for Production of Fermentable Sugars

Abstract

Brewer’s spent grain (BSG) is a residue produced in large amounts by the brewing industry and may be used in bioprocesses as a source of sugar due to its chemical composition. The objectives of this work were to determine the chemical composition of BSG and to investigate its potential in obtaining fermentable sugars through enzymatic hydrolysis. For this purpose, mechanical stirring, direct and indirect ultrasound processes were studied to evaluate the efficiency of BSG enzymatic hydrolysis. Operational variables of mechanical stirring (temperature, enzyme and substrate concentrations) and ultrasound (pulse factor and amplitude) systems were analyzed. The highest sugar yield was 370.9 g kg−1 using direct sonication system at a pulse factor of 0.23 and oscillation amplitude of 50%. Sugar yield in direct ultrasound system was 2.6 and 4.9 times greater than indirect sonication and mechanical stirring systems, respectively. For BSG hydrolysis using enzymes, direct sonication presented better results than mechanical stirring and indirect sonication processes. Besides, the treatment time using direct sonication was diminished, confirming that it is a promising technology for improving the yields of fermentable sugars from BSG.