A sustainable process for enzymatic saccharification of ionic liquid-pretreated cellulosic materials

Abstract

A two-step sustainable process for the enzymatic saccharification of lignocellulosic materials (e.g., crystalline cellulose, paper and corn cob) was evaluated. In the first step, pretreatment of crystalline cellulose, paper and lignocellulose by the ionic liquid (IL) 1-butyl-3-methylimidazolium chloride, [Bmim][Cl], was carried out to obtain an amorphous substrate. This step included the recovery of the IL for further reuse. Then, the amorphous cellulosic materials were hydrolyzed by different industrial enzyme preparations. The pretreatment of cellulose, paper and lignocellulose (corn cob) with [Bmim][Cl] led to an up to 2.5-fold increase in the yield of the enzymatic hydrolysis, compared to the same substrate without pretreatment; this produced nearly 100% hydrolysis. The combined action of Celluclast 1.5L (cellulase from Trichoderma reesei) and Novozyme 188 (cellobiase from Aspergillus niger) was essential in the process of enzymatic saccharification of corn cob. By combining the enzyme complex Ultraflo L (β-endoglucanase from Humicola insolens mixed with arabanase and xylanase enzymes) with Celluclast 1.5L and Novozyme 188, the soluble sugar concentration was increased 1.5-fold, resulting in the best choice for enzymatic saccharification of lignocellulosic materials. The effectiveness of lignocellulose pretreatment with [Bmim][Cl] for improving enzymatic saccharification yield was also confirmed.