Steam Pretreatment of Rice Hulls to Release Fermentable Saccharides: An Approach to Improve Recovery of (Hemi)Cellulosic Sugars Through Multivariate Design

Abstract

The conversion of rice hulls into fermentable saccharides was explored through steam pretreatment employing 2.5% SO2. The interaction between temperature and time was assessed by means of the response surface method to achieve optimum contents of C6-sugars in water-insoluble solids (WIS) and C5-sugars in the liquor. Pretreatment carried out at 218 °C for 2.3 min released liquor containing 55.4 g/L of sugars (29.1 g/L of xylose). In parallel, the WIS was subjected to enzymatic saccharification using different solid and enzyme loads via an experimental design: assays using 22.0% WIS and 20.0 filter paper units (FPU)/g led to 90.6 g/L of glucose, corresponding to a yield of 86.4% and an overall yield of 72.4%. The data reported are the highest ever found for such raw material, making it attractive to compete with conventional lignocellulosic biomass.

Keywords

• lignocellulosic feedstock
• sulfur dioxide
• high solid loading
• hydrolysis
• central composite rotatable design