Pilot-scale xylooligosaccharide production through steam explosion of screw press–dried brewers’ spent grains

Brewers’ spent grains (BSGs) represent the largest quantity of solid waste from brewing, while xylooligosaccharides (XOS) produced from BSG show promising applications in food, beverage and health products. Production of XOS from a Weiss and malt BSG was scaled-up in steam explosion hydrothermal treatment using process conditions from bench-scale liquid hot water optimisations in stirred batch reactors. Three levels of moisture (15, 25 and 32% dry matter) achieved by screw press dewatering were evaluated by varying the treatment temperatures and times. Results show the highest XOS yields (> 73.1%) were obtained, for both BSGs, at process condition selected (180 °C, 10 min) with 25% initial dry matter content. These yields were higher than reported bench-scale optimisations (61%), but obtained using 60% less water; hence, initial dry matter content was an important variable affecting XOS yield. The pilot-scale steam explosion results provide a departing point for a cost-effective commercial production of XOS from BSG.