Chlorine dioxide oxidation of hemicellulose from alkaline hydrolysate bagasse to remove lignin unit in lignin-carbohydrate complex

Abstract

Owing to the existence of lignin-carbohydrate complex (LCC) linkages, the extracted hemicellulose contains lignin, which is difficult to remove. Chlorine dioxide selectively oxidizes lignin without reacting with carbohydrates. In this study, chlorine dioxide was used to remove lignin from the hemicellulose sample. Ion chromatography and 2D-HSQC NMR were used to observe the changes in the LCC. After chlorine dioxide treatment, acid-insoluble lignin was largely degraded, with a removal rate reaching 68%. Furthermore, the 2D-HSQC NMR spectrum showed that guaiacyl (G) lignin underwent dramatic degradation and degradation of syringyl (S) lignin was also obvious. Phenyl glycoside-type LC linkages were also largely degraded. Moreover, the sugar composition and structure of the hemicellulose did not change significantly. This suggests that it is feasible to remove lignin from LCCs through oxidation of hemicellulose using chlorine dioxide. Meanwhile, hemicellulose with high molecular weight and high purity can be obtained by this method.