Molecular weight distribution of wood components extracted from Pinus taeda biotreated by Ceriporiopsis subvermispora

Abstract

Significant contributions have been made to understand the ligninolytic system of the biopulping fungus, Ceriporiopsis subvermispora; however, the reason why this fungus selectively degrades lignin is still unclear. This study evaluates the depolymerization of wood components induced by C. subvermispora during wood decay under solid-state fermentation. Pinus taeda wood chips were biotreated for periods from 15 to 90 days. The fungus degraded lignin and extractives extensively without removing large amounts of glucan. Alpha-cellulose samples were prepared from decayed and undecayed wood chips for evaluation of cellulose depolymerization. The yields of alpha-cellulose decreased from 47.8% for undecayed wood to 42.6 and 34.2% for the wood samples biotreated for 30 and 90 days, respectively. High performance size exclusion chromatography of tricarbanyl derivatives of these alpha-cellulose preparations indicated a progressive decrease in the polymerization degree values from the 30th day of biotreatment. Lignin depolymerization, evaluated by gel permeation chromatography (GPC) of residual MWLs, was rapid in the first 30 days of biodegradation. After this period an extensive mineralization occurred. Some relevant hydrolytic and oxidative enzymes present in the culture extracts were studied. Xylanase was the main hydrolytic enzyme produced, while laccase was not detected in any biodegradation period evaluated. A correlation between the levels of wood-degrading enzymes produced and the pattern of wood constituents degradation was tentatively established.