Understanding the natural durability of some African tropical heartwoods toward Pycnoporus sanguineus and Antrodia sp.: lignin structure and cellulose morphology control

摘要

The natural durability of the heartwoods from Testulea gabonensis Pellgr. ( T. gabonensis ), Julbernardia pellegriniana ( J. pellegriniana ), Aucoumea klaineana Pierre ( A. klaineana ), and Tieghemella africana Pierre ( T. africana ) widely used for windows, door frames, frameworks, closets, cupboards and plywood in the Congo Basin or other countries in the world were studied. The samples were exposed to Pycnoporus sanguineus ( P. sanguineus ) and Antrodia sp. Factors such as extracts toxicity, lignin syringyl to guaiacyl (S/G) ratio, cellulose crystalline, and fibers morphology which control the resistance of the wood toward white- and brown-rot fungi were investigated. Unextracted woods displayed a strong natural durability against P. sanguineus compared to Antrodia sp., except for A . klaineana which didn’t show significant difference concerning its durability against the white- or the brown-rot fungus. Unextracted heartwoods from T. gabonensis and T. africana were very durable against P. sanguineus ; they contain extracts with strong toxicity toward that white-rot fungus. However, A . klaineana and J. pellegriniana heartwoods were moderately resistant to P. sanguineus . For the extracted heartwoods, the lowest mass loss against P. sanguineus was achieved by T. gabonensis heartwood which was the richest in G type units. The highest mass loss was obtained from the three other heartwoods displaying the highest content on S units. Heartwoods with high crystallinity index and long cellulose fibers were more resistant to Antrodia sp. compared to A. klaineana which displayed the shortest cellulose fibers (624?μm) and the lowest crystallinity index (59%).