Degradation of Wood and Pulp by Three Fungi, Pycnoporus cinnabarinus, Trichophyton rubrum LKY-7 and Trichophyton rubrum LSK-27

Abstract

Degradation of pine, yellow poplar and sweet gum by three fungi Pycnoporus cinnabarinus, Trichophyton rubrum LKY-7 and Trichophyton rubrum LSK-27 was investigated. The two Trichophyton species have not been identified, i.e., they are unknown. However, they have been putatively characterized with a chemical signature method. Their chemical signatures were compared to known fungi in a database of Microbe Inotech Labs, Inc. (St. Louis, MO). P. cinnabarinus degraded pine block samples much faster than T rubrum LKY-7 and T. rubrum LSK-27, whereas P. cinnabarinus and T rubrum LSK-27 degraded yellow poplar and sweet gum at almost the same rate. Among three fungi, LKY-7 had the lowest ability to degrade all three types of wood. In an effort to get a better understanding of how fungi degrade lignin in wood, contents of various functional groups were analyzed. After three-months of degradation of pine flour by the three fungi, the following changes were observed: an increase in condensed phenolic OH group content and carboxylic acid group content, a decrease in the guaiacyl phenolic OH content, and little change of aliphatic OH group content. Further studies in the degradation of pine flour by P. cinnabarinus revealed that the increase in condensed phenolic OH group content and the decrease in guaiacyl phenolic OH group content occurred in the first month of the degradation. The changes of functional group contents in the degradation of unbleached softwood kraft pulp by P. cinnabarinus had the same trends as those in the degradation of pine flour. In other words, structural alterations of lignin due to the kraft pulping process had little effect on how P. cinnabarinus degraded lignin. Action modes in the fungal degradation of lignin are discussed.