Mild sodium carbonate pretreatment of wheat straw for improving cellulose and xylan enzymatic hydrolysis

Abstract

In order to enhance enzymolysis saccharify, the impact of pretreating wheat straw with sodium carbonate (Na₂CO₃) at moderate temperatures was investigated. The effects of pretreatment condition, for instance, reaction time (10–120 min) and temperature (75–105 °C) were investigated on delignification and polysaccharides (cellulose and hemicellulose) protection. It was found that the wheat straw effectively achieved the recovery of 82.67 %, 89.70 %, and 71.11 % for total sugar, cellulose, and hemicellulose respectively, and removed of 54.96 % lignin after pretreatment at the temperature of 90 °C with 4 % (w/v) Na₂CO₃ for 120 min. After a 20 FPU enzymes saccharification for 72 h, the highest enzymatic digestibility of cellulose and xylan for pretreated residues were 81.8 % and 82.4 %, significantly higher than that of the raw material (16.48 % cellulose enzymatic digestibility, 8.43 % xylan enzymatic digestibility). The enzymatic hydrolysis results also demonstrated that the removal and polydispersity of lignin affected the conversion efficiency of the raw material, and delignification degree was positively correlated to enzymatic hydrolysis efficiency within a certain range. This pretreatment has potential for C6 and C5 sugars co-fermentation of wheat straw for biorefinery.