Behavior of the Brown-rot Fungus Gloeophyllum trabeum on Thermally-modified Eucalyptus grandis Wood

Fred Willians Calonego,Marli Teixeira De Almeida Minhoni,Elias Taylor Durgante Severo,Cinthia Dias Rocha,Djanira Rodrigues Negrão,Meire Cristina Nogueira De Andrade,João Vicente Latorraca

doi:10.4322/floram.2013.028

Abstract

In this study, we aimed evaluate the behavior of the brown-rot fungus Gloeophylum trabeum and white-rot fungus Pycnoporus sanguineus on thermally-modified Eucalyptus grandis wood. To this end, boards from five-year-eleven-month-old E. grandis trees, taken from the Duratex-SA company stock, were thermally-modified between 180 °C and 220 °C in the Laboratory of Wood Drying and Preservation at Universidade Estadual Paulista - UNESP, Botucatu, Sao Paulo state Brazil. Samples of each treatment were tested according to the ASTM D-2017 (2008) technical norm. The accelerated decay caused by the brown-rot fungus G. trabeum was compared with the decay caused by the white-rot fungus P. sanguineus, studied by Calonego et al. (2010). The results showed that (1) brown-rot fungus caused greater decay than white-rot fungus; and (2) the increase in temperature from 180 to 220 °C caused reductions between 28.2% and 70.0% in the weight loss of E. grandis samples incubated with G. trabeum.

Highlights

The mechanism of wood degradation differs fundamentally between brown and white rot fungi
The weight loss data of Eucalyptus grandis wood caused by the action of the brown-rot fungus G. trabeum was normally distributed and analysis of variance with a randomized block design was used, taking into account the thermal treatments, as well as Tukey’s test at 5% significance level for the comparison of the means
The values for the amount of weight loss in untreated Eucalyptus grandis wood, found in Table 1, were 50.33% and 34.32% for the samples incubated with the brown-rot and white-rot fungi, respectively

Summary

Introduction

The mechanism of wood degradation differs fundamentally between brown and white rot fungi. The brown-rot fungi selectively removes cellulose and hemicelluloses compounds, whereas the white-rot fungi causes degradation of all cell wood components (Oliveira et al, 1986; Barreal, 1998). The white-rot fungus Pycnoporus sanguineus (L.) Murrill is a good producer of phenoloxidase, and preferentially degrades lignin (Esposito et al, 1993). According to Oliveira et al (1986), Barreal (1998) and Kleman-Leyer et al (1992), the whiterot fungus attacks the surfaces of the microfibrils resulting in a progressive erosion of the polymers of wood. The brown-rot fungus completely cleaves the amorphous regions of the cellulose microfibrils, and subsequently, promotes significant loss in wood weight because of degradation in the crystalline region of the cellulose. At advanced stages of decay, the structural polysaccharides are quantitatively removed, and a modified lignin residue remains

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