Pseudo lignin formed from hygrothermally treated holocellulose and its effect on fungal degradation

Abstract

Hygrothermal processes are widely used in modification of wood or other lignocellulosic materials to improve their decay resistance and dimensional stability. However, the mechanism behind the improved decay resistance is still unclear. In this study, hygrothermal modification of holocellulose was carried out at different temperature (℃) -duration (min) combinations (180−60, 220−60, 220−180), and the formation of pseudo lignin in modified holocellulose was verified. Its yield, as indicated by the acid insoluble substance, increased with the intensity of the hygrothermal modification from 0.11% for untreated holocellulose to 3.85%, 24.13%, and 65.86% for 180–60, 220–60, 220–180, respectively. According to the results of HPLC, FTIR, solid 13C NMR, 31P NMR, XRD and Py-GC-MS, the formed pseudo lignin contains polyfuran, aromatic, carbonyl and aliphatic structures. The formation pathway of pseudo lignin was proposed. It exhibited a significant inhibition effect against Gloeophyllum trabeum (brown rot fungus) with reduced mass losses from 6.89% for untreated holocellulose to 6.43%, 1.09% and 0.03% for 180–60, 220–60, 220–180, respectively; however, the inhibition effect against Coriolus versicolor (white rot fungus) was much less obvious. This provides an innovative point of view to explain the fungal degradation behavior of thermally modified wood or other carbohydrate materials.