Pretreatment of Miscanthus by NaOH/Urea Solution at Room Temperature for Enhancing Enzymatic Hydrolysis

Abstract

A novel pretreatment process using NaOH/Urea solution at room temperature was developed to overcome recalcitrance of lignocellulose for efficient bioconversion of miscanthus. The process consists of mechanical size reduction, pretreatment with NaOH/Urea solution, and filtration. The results indicated that the substrate enzymatic digestibility (SED) of miscanthus pretreated with 8 wt% NaOH and 12 wt% urea at 21 oC for 30 min was up to 71.99 % at low enzyme loading of 5 filter paper units (FPU)/g glucan after 72 h hydrolysis. NaOH/Urea pretreatment efficiently removed lignin and hemicellulose. And their removal rates increased with the increase of pretreatment temperature, NaOH dosage and urea dosage. With the increase of NaOH dosage, the chemical composition removal rate decreased in the following order: lignin, xylan, araban, galactan. Meanwhile, NaOH/Urea pretreatment could open up the fiber structure, decrease cellulose crystallinity index, and prevent lignin droplets depositing on cellulose. The optimal condition for the NaOH/Urea pretreatment regarding this study was 6 wt% NaOH/12 wt% urea and 21 °C. Approximately 70 % glucose yield was achieved upon this condition.