Statistical optimization of aqueous ammonia pretreatment and enzymatic hydrolysis of corn cob powder for enhancing sugars production

Response surface methodology (RSM) was applied to systematic optimization of aqueous ammonia pretreatment and enzymatic hydrolysis of corn cob powder (CCP) using self production cellulases from Aspergillus niger HQ-1. Significant variables including aqueous ammonia concentration, temperature and time during pretreatment were screened and optimized. Results showed that CCP with 0.3 mm of particle size should be pretreated using 11.6 wt % aqueous ammonia solution with 20.0% (w/v) of solid loading at 71.3 degrees C for 8.8 h. The optimized pretreatment conditions could result in 97.1% of cellulose recovery, 66.6% of hemicellulose recovery and 75.7% of lignin removal, respectively. Significant variables including enzyme loading, reaction time and biomass loading during enzymatic hydrolysis were also screened and optimized. Maximal reducing sugar (822.31 mg/g dry substrate, mg/gds) and xylose (316.72 mg/gds) could be obtained while the pretreated CCP was hydrolyzed at 50.0 degrees C, pH 4.8 for 36.6 h with 10.9 FPU/gds (FPU/g dry substrate) of enzyme loading, 6.95% (w/v) of biomass loading and 0.5% (w/v) of Tween-80. The optimized enzymatic hydrolysis conditions could result in 92.1% of holocellulose conversion and 79.3% of hemicellulose conversion, respectively. In addition, results also indicated that the crude cellulases solution containing xylanases from A. niger HQ-1 could be applied to enzymatic hydrolysis of the pretreated CCP.