Oxidative Pretreatment of Spruce to Facilitate Enzymatic Hydrolysis of Polysaccharides

Brown rot fungi employ extracellular Fenton oxidation systems to degrade the wood cell wall structure, exposing structural polysaccharides to the action of hydrolytic enzymes. In an attempt to improve the enzymatic accessibility of cellulose and hemicelluloses by partially degrading the wood cell walls with an oxidative pretreatment, spruce pin chips and wood meal were treated with autoxidation, Fenton oxidation, and peracetic acid (PAA) oxidation. The extent of polysaccharide accessibility was assayed by hydrolyzing treated wood samples with Cellulysin and determining the amount of glucose released with high pH anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD). Autoxidation and Fenton oxidation did not significantly increase the hydrolytic glucose yield, while PAA treatment afforded a slight increase in the amount of released glucose. Aromatic and dibasic acid lignin degradation products in the MeCl2 extracts of PAA oxidation filtrates were identified with gas chromatography-mass spectrometry (GC-MS), with vanillin and vanillic acid appearing as the predominant products. GC-MS analysis of MeCl2 extracts of the autoxidation and Fenton oxidation yielded only trace amounts of vanillin. Attempts to detect methanol in the oxidation product solutions yielded negative results