Reduced pretreatment severity and enzyme loading enabled through switchgrass pelleting

This study investigated the effectiveness of low severity alkaline pretreatment conditions and reduced cellulase and hemicellulase loadings on glucose and xylose yields from pelleted switchgrass. Pelleting improved the efficacy of soaking in aqueous ammonia pretreatment enabling milder pretreatment and lower enzyme loadings to obtain high sugar yields. Although 80% glucose yields could be achieved with cellulase alone, hemicellulase addition improved yields from pelleted switchgrass to above 90% at cellulase loadings as low as 10 FPU g−1 glucan. Similar efficacy was found with higher cellulase loadings and reduced hemicellulase loading. Xylose yields greater than 80% were achieved with cellulase loadings greater than 14 FPU and 200 XU g−1 glucan. This study demonstrated that biomass pelleting can enable biorefineries to use less severe pretreatment conditions and reduced enzyme loadings while maintaining high hydrolysis yields. Models were developed to quantify the range of cellulase and hemicellulase loadings to achieve chosen glucose and xylose yields.