Effect of Biological Pretreatment with White-rot Fungus Trametes hirsuta C7784 on Lignin Structure in Carex meyeriana Kunth

Abstract

Carex meyeriana Kunth was subjected to biological pretreatment with the white-rot fungus Trametes hirsuta C7784, and the structural changes of the lignin were investigated. Results showed that there was a slight decrease in carbohydrate content after pretreatment for 3 weeks, but a noticeable decrease in lignin and carbohydrate contents after 6 weeks. Detail structural analysis of the isolated lignin from the samples revealed that Carex meyeriana Kunth lignin consisted mainly of p-hydroxyphenyl (H), guaiacyl (G), and syringyl (S) units with minor p-coumarate and ferulate units. The predominant lignin interunits were β-O-4′ ether linkages, followed by phenylcoumaran, together with a lower portion of resinol and tricin substructures. After pretreatment for 6 weeks, the contents of β-β′ and β-5′ linkages notably decreased, suggesting that the fungus preferentially attacked these linkages. The pretreatment led to an increase of S/G ratio from 0.64 in the control to 0.83 in the sample pretreated for 6 weeks. The comprehensive understanding of the structural changes of lignin offers new insights into the biological degradation of Carex meyeriana Kunth by white-rot fungus.