Sugar yields from dilute sulfuric acid and sulfur dioxide pretreatments and subsequent enzymatic hydrolysis of switchgrass

Abstract

Dacotah switchgrass was pretreated with sulfuric acid concentrations of 0.5, 1.0, and 2.0wt.% at 140, 160, and 180°C and with 1 and 3wt.% sulfur dioxide at 180°C over a range of times. Sulfur dioxide loadings of 0%, 1%, 3%, 5%, and 10%wt.% of dry biomass were also tested at 180°C for 10min. Sugar yields were tracked for pretreatment and subsequent enzymatic hydrolysis to identify conditions for the highest total sugar yields. Pretreatment with 1wt.% dilute sulfuric acid at 140°C for 40min followed by enzymatic hydrolysis with 48.6mg enzyme/g initial glucan in raw biomass resulted in ∼86% of theoretical yield for glucose and xylose combined. For sulfur dioxide pretreatment, the highest total sugar yield of about 87% occurred at 5% SO2 for 10min and 180°C. However, xylose yields were higher at shorter times and glucose yields at longer times.