Acid Bisulfite Pretreatment of Eastern Redcedar for Fermentable Glucose Production: Optimization through Response Surface Methodology

Abstract. Eastern redcedar is considered a nuisance by many landowners in the U.S. Central Plains, and processes that add value to this softwood tree are actively being sought. The primary goal of this study was to determine the optimal pretreatment conditions to efficiently obtain glucose from eastern redcedar. Response surface methodology (RSM) based on a uniform precision rotatable central composite design (CCD) was used to design the experiments and analyze the influence of four pretreatment process variables (pretreatment temperature, hold time, sulfuric acid loading, and sodium bisulfite loading) on wood glucan-to-glucose yields. The highest wood glucan-to-glucose yield of 91% was predicted at the optimum conditions of 200°C, 7.5 min of hold time, 3.75 g sulfuric acid 100 g^-1 dry wood, and 22.5 g sodium bisulfite 100 g^-1 dry wood. The prediction model was validated by conducting experiments at the optimized conditions, resulting in 87% ±2% of theoretical wood glucan-to-glucose yield. Mass balances calculated 70% delignification and 89% to 100% loss of hemicellulose polymers during pretreatments.