Natural Durability studies and Changes in wood chemistry of some Ghanaian hardwoods during decay by white- and brown-rot fungi

IRG/WP 04-10542

Zeen Huang, K Maher, S A Amartey

The natural decay resistance of Esa (Celtis mildbraedii), Wawabima (Sterculia rhinopetela) and Dahoma (Piptadeniastrum africanum) obtained from Ghana was determined according to BS EN 113 (1997). Esa was found not durable to the white-rot, but very durable to the brown-rot; Wawabima was very durable to both white- and brown-rots; and Dahoma was durable to the white-rot, and very durable to the brown-rot. The natural durability ratings for the timbers in accordance with BS EN 350-1 (1994) are: Esa 5, Wawabima 1, and Dahoma 2. Changes in chemical composition of Esa (which has the lowest durability), when exposed to the different decay fungi at various stages of decay, were studied using HPLC, FT-IR and gravimetric methods. Results of the gravimetric and FT-IR analysis suggested that, generally, the white-rot fungi (Trametes versicolor and Phanerochaete chrysosporium) degraded the cellulose, hemicelluloses and lignin simultaneously. The brown-rot fungus (Coniophora puteana) however, degraded the cellulose and hemicellulose and left the lignin virtually untouched. The HPLC results revealed that Trametes versicolor and Phanerochaete chrysosporium degraded the cellulose component (glucose) and the main hemicellulose component (xylose and mannose) at similar rates. However, the brown-rot fungus, Coniophora puteana degraded mannose faster than glucose and xylose. Changes in the components of the branch chains of the hemicelluloses were found to be different according to the various fungi. However, in all cases, rhamnose was consumed faster than the other components, arabinose, galactose and 4-O-methyl-glucuronic acid, at the early stages of decay.

Keywords: Lesser-utilised tropical hardwoods; natural durability; fungi; wood chemistry; HPLC; FT-IR

Conference: 04-06-06/10 Ljubljana, Slovenia

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