Study on the effect of combined and free lignin to the cellulose enzymatic hydrolysis

This study compares the behavior of combined and free lignin on the cellulose enzymatic hydrolysis (EH). The combined lignin refers to the lignin naturally existed in the lignocellulose and the free lignin refers to the cellulolytic enzyme lignin. Three kinds of lignocelluloses (i.e., Moso bamboo, horsetail pine and aspen) are chosen for the research. Lignin is mainly biosynthesized of guaiacyl (G), syringyl (S), and p-hydroxyphenyl (H) structural units. The HSQC NMR analysis shows that the free lignin of Moso bamboo, horsetail pine and aspen are mainly composed of G-S-H, G-H and G-S type lignin units, respectively. Furthermore, a blood glucose meter (BGM), UV and fluorescence spectrophotometer are used to determine the cellulose conversion, enzyme adsorption and fluorescence intensities in the EH. It shows that the combined lignin has a weaker inhibitory effect on the EH breakdown than the free lignin. The influence of EH follows the order of Moso bamboo > aspen > horsetail pine. This study can be applied to the development of theoretical guidelines for mitigating the residual prohibition of lignin in the lignocellulose EH.