Skip to main content
SLU publication database (SLUpub)

Research article2018Peer reviewed

Effect of thermal modification on the micromorphology of decay of hardwoods and softwoods by the white rot fungus Pycnoporus sanguineus

Gao, Jie; Kim, Jong Sik; Daniel, Geoffrey

Abstract

Thermal modification (TM) of wood at high temperatures can lead to significantly improved decay resistance against white rot (WR) fungi, but little is known about the mechanism of this improvement at the cellular level. As a contribution to this topic, hardwoods (HWs) (ash, beech) and softwoods (SWs) (spruce, fir) were submitted to the Termovuoto (R) TM process at 220 degrees C for 3-4 h (shortly TMW220 degrees c) and were degraded by the WR fungus Pycnoporus sanguineus. The results were studied using microscopy techniques. Decay occurred preferentially via cell wall delignification prior to the removal of cellulose and hemicelluloses. Concerning this effect and fungal colonization, there were no essential differences between TMW220 degrees c and the unmodified reference of all wood species. TMW220 degrees c, however, showed a number of characteristic changes in decay morphology. Narrow and distinct concentric transition zones were observable in decayed fiber and tracheid cell walls, which demark the lignified and delignified regions. Moreover, cell wall separation by preferential delignification of compound middle lamellae (CML) was not seen in decayed tracheids. It can be concluded that the Termovuoto TMW220 degrees c process has an impact on the delignification process of P. sanguineus at the cell wall level, which slows down the decay.

Keywords

decay resistance; delignification; Pycnoporus sanguineus; thermal modification (TM); thermally modified wood (TMW); white rot decay

Published in

Holzforschung
2018, Volume: 72, number: 9, pages: 797-811
Publisher: WALTER DE GRUYTER GMBH