Caracterização do ataque de fungos apodrecedores de madeiras através da colorimetria e da espectroscopia de infravermelho

Abstract

RESUMOAmostras de madeiras de marupá (Simarouba amara) e andiroba (Carapa guianenis) foram submetidas ao ataque dos fungos Trametes versicolor (podridão branca) e Gloeophylum trabeum (podridão parda). A colorimetria foi empregada para determinar as cores das madeiras antes e após o ataque dos fungos. Para acompanhar a variação do teor dos compostos químicos foi utilizada a técnica de espectroscopia de refletância difusa no infravermelho médio. Ambas as espécies foram consideradas não resistentes ao fungo de podridão branca. Para o fungo de podridão parda, a andiroba foi considerada resistente e o marupá não resistente. Ambas as espécies de madeira se apresentaram mais escuras após o ataque do fungo Gloeophyllum trabeum. Já o ataque do fungo Trametes versicolor causou clareamento na madeira da andiroba e escureceu ligeiramente o marupá. Os resultados da análise dos espectros de infravermelho mostraram que em ambas as espécies de madeira houve redução na intensidade das bandas de celulose, hemiceluloses e lignina após o ataque do Trametes versicolor, e redução somente na intensidade da banda de celulose após o ataque do Gloeophyllum trabeum. Palavras-chave: biodeterioração; podridão parda; podridão branca; técnicas não destrutivas. ABSTRACTWood samples of marupá (Simarouba amara) and andiroba (Carapa guianenis) were submitted to Trametes versicolor (white rot) and Gloeophylum trabeum (brown rot) fungi attack. Colorimetry was used to determine the color of the wood before and after wood decaying fungi. To evaluate the changes in chemical compounds levels in the wood samples, the diffuse reflectance medium infrared spectroscopy was used. Both wood were non resistant against white rot fungus, while with brown rot attack andiroba was resistant and marupá was not. After Gloeophyllum trabeum attack both woods changed to a darken color, and after Trametes versicolor attack andiroba changed to a lighter color and marupá darkened slightly, The analysis showed a reduction in the peak intensity of cellulose, hemicellulose and lignin, for both species, after Trametes versicolor attack and a reduction in the peak intensity of cellulose after Gloeophyllum trabeum attack.

Resistência Biológica E Colorimetria Da Madeira Termorretificada De Duas Espécies De Eucalipto1

“…Essa mudança nos parâmetros colorimétricos após o ataque de fungos apodrecedores da madeira já foi verificada por Costa et al (2011), submetendo as madeiras de Simarouba amara (marupá) e Carapa guianensis (andiroba) ao ataque de Trametes versicolor e Gloephyllum trabeum. Na madeira de marupá houve escurecimento após o ataque de ambos os fungos, enquanto na de andiroba ocorreu escurecimento apenas após o ataque de G. trabeum.…”

Fourier transform infrared spectroscopy in treated woods deteriorated by a white rot fungus

“…Aiming to facilitate an understanding of the variations to the chemicals components of the woods subjected to deterioration, together with the spectra, and to increase the reliability of the results, a complementary analysis was developed from the chemical compounds' relative intensities variations. 890 cm -1 (cellulose), 1420 cm -1 (polyoses) and 1740 cm -1 (carbonyls) bands were observed, and the 1508 cm -1 band (lignin) was selected as a reference, since, according to Costa et al (2011), it is characterized by high purity.…”

“…To assist the analysis of changes to wood chemical components after fungal deterioration, authors such as Pandey and Pitman (2003) and Costa et al (2011) used a relationship between the variations in the lignin and carbohydrate ratios, through the peaks of relative intensities in the bands of interest, which makes it possible to verify the deterioration mechanisms by the employed rot fungus.…”

“…Ciencia y tecnología 20(3): 479 -488, 2018 Universidad del B í o -B í o Maderas. Ciencia y tecnología 20(3): 479 -488, 2018According to Costa et al (2011), the decrease of the lignin / carbohydrate ratio is due to a preference of the rot fungus to deteriorate the lignin at a higher rate, in detriment of the other components, such as cellulose and hemicellulose.However, in the present study, it was verified that the ratios showed a reduction and an increase in their values, possibly indicating a simultaneous deterioration of the chemical compounds of the wood, which corroborates with Schmidt (2006) and Pandey and Nagveni (2007), who highlight that in simultaneous white rot fungi, lignin and carbohydrates are removed at a similar rate, causing a homogeneous deterioration of the wood.…”

“…According to Costa et al (2011), the decrease of the lignin / carbohydrate ratio is due to a preference of the rot fungus to deteriorate the lignin at a higher rate, in detriment of the other components, such as cellulose and hemicellulose.…”