Combination of xylanase and cellulase hydrolysis for enhanced saccharification of poplar chips: Process optimization

Removing xylan from the outer surface of cellulose could promote the accessibility of cellulase to cellulose. Under this premise, in order to develop an efficient pretreatment method to obtain fermentable reducing sugar from poplar fiber, a response surface methodology was created via the combination of the Plackett-Burman design and the Box-Behnken design and was utilized by the Design-Expert software. The optimum conditions were as follows: a liquid-solid ratio of 4.95 to 1 (mL/g), a pre-hydrolysis xylanase temperature of 70.3 °C, and a total hydrolysis time of cellulase of 52.9 h. Under these conditions, the maximum amount of reducing sugars converted from poplar fiber was 159.6 mg/g. The average amount from the validation results was 160.1 mg/g, which was in agreement with the predicted value. Meanwhile, the poplar fiber hydrolyzed via a xylanase-aided two-stage pretreatment was compared with the poplar fiber hydrolyzed via only a cellulase pretreatment, using scanning electron microscopy. The xylanase-aided treatment revealed a surface with a more damaged structure, indicating that the utilization of xylanase could further improve the effects of hydrolysis on poplar fibers.