Effects of Dilute Acid Pretreatment Parameters on Sugar Production during Biochemical Conversion of Switchgrass Using a Full Factorial Design

Pretreatment is an important unit operation in the production of cellulosic fuels because it governs the efficiency of the overall conversion process. The effect of dilute acid pretreatment parameters on prehydrolyzate xylose and glucose concentrations, as well as on glucan content and digestibility of pretreated switchgrass, was determined using a full factorial design. Temperature varied from 140 to 180 degrees C; time ranged from 10 to 40 min; and sulfuric acid concentrations changed from 0.5% or 1% (v/v). Results showed that pretreatment temperature was a significant factor on all response variables. Moreover, the prehydrolyzate xylose levels that reached the maximum of 21.71 g/L were also significantly impacted by pretreatment time, while remaining insensitive to changes in acid concentration. A three-way interaction between all the pretreatment factors significantly affected prehydrolyzate glucose concentrations, which ranged from 1.52 to 11.34 g/L. The glucan content of pretreated switchgrass decreased from 64.3% to pretreatment conditions increased in severity, while switchgrass digestibility rose up to 95.8%. The temperature-acid concentration interaction significantly impacted glucan content, whereas digestibility was affected by the temperature-time interaction. Overall, this study provided useful insights to select dilute acid pretreatment conditions to convert switchgrass into fermentable sugars.