Evaluation of degradation products and structural changes of ethanol organosolv lignin by white rot fungus, Fomitopsis insularis

Lignin, one of major components of lignocellulose, is the most abundant phenyl propanoid polymer. It contains three precursors, aromatic alcohols including coniferyl alcohol, sinapyl alcohol and ρ-coumaryl alcohol. Three different monomers are polymerized by ether bond linkage and carbon-carbon bond linkage, which contribute to recalcitrance of lignin. Recalcitrant lignin polymer needs to be modified and degraded for industrial application. Among various modification processes, white rot fungi are well-known for degrading lignin selectively.

The objectives of this study were to examine structural changes of ethanol organosolv lignin (EOL) by Fomitopsis insularis with addition of antioxidant and to identify the metabolites produced during degradation of EOL. EOL used in this study is relatively pure and sulfur free, and has low molecular weight, which allows microorganisms to easily access and modify EOL.

Based on our previous research, F. insularis had a possibility of biomodification of EOL, however caused polymerization of EOL. In this study, ascorbic acid, one of antioxidants, was added for blocking the polymerization by radicals formed by cleavage of bonds. The structural changes in EOL by fungus will be analyzed using FT-IR and gel permeation chromathgraphy to evaluate functional groups and molecular weight. The changes in ether bonds and phenolic hydroxyl groups also will be analyzed by the nitrobenzene oxidation method and aminolysis reaction, respectively. Furthermore, degradation products of EOL by F. insularis will be analyzed by chromatography. Consequently, this study is expected to help to understand the biomodification characteristics of EOL by white rot fungus with addition of antioxidant.