Optimizing acid-catalyzed steam explosion to enhance enzymatic hydrolysis of Populus euramericana by response surface methodology

Poplars (Populus euramericana) have been touted as an important bioenergy crop based on its potential utility as a short-rotation woody crop and genetic improvement advances. In this study, acid-catalyzed steam explosion was investigated and optimized for the pretreatment of Populus euramericana using response surface methodology. The reaction parameters studied were sulfuric acid concentration (0.1-1%), temperature (200-225 °C) and time (1-10 min). The process was optimized for cellulose recovery and glucose conversion obtained by enzymatic hydrolysis on the pretreated Populus euramericana by Celluclast (1.5 L) and Viscozyme L. The analysis of variance (ANOVA) revealed that, among the process variables, time and temperature have the most significant effect on the cellulose recovery and glucose conversion whereas sulfuric acid concentration observed significantly lower effect on the two responses. Proposed quadratic model to predict cellulose recovery and glucose conversion from Populus euramericana had a high F and R²values indicating that the model has the ability to represent the relationship among the independent variables studied. The optimum conditions for cellulose recovery were determined to be sulfuric acid concentration 0.6%, temperature 208.5 °C and time 6.2 min. Also, the optimum conditions for glucose conversion were determined to be sulfuric acid concentration 0.7%, temperature 212.7 °C and time 9.1 min. The optimum acid-catalyzed steam explosion condition improves glucose conversion by three times compared to that from raw material (from 26.0% to 72.6%).