Effects of incubation time and temperature on in vitro selective delignification of silver leaf oak by Ganoderma colossum

• Published in: Applied and Environmental Microbiology 1995-01, Vol.61 (1), p.138-144
• Main Authors: Adaskaveg, J.E. (University of California, Davis, CA.), Gilbertson, R.L, Dunlap, M.R
• Format: Article
• Language: English
• Subjects: Biochemistry; BIODEGRADACION; BIODEGRADATION; Biological and medical sciences; Biology of microorganisms of confirmed or potential industrial interest; Biotechnology; BOIS; Botany; CELLULOSE; CELULOSA; CHAMPIGNON; ELABORACION DE PULPA; Fundamental and applied biological sciences. Psychology; Fungi; GANODERMA; HONGOS; LIGNINAS; LIGNINE; MADERA; MICROORGANISME; MICROORGANISME THERMOPHILE; MICROORGANISMOS; MICROORGANISMOS TERMOFILOS; Mission oriented research; Physiology and metabolism; QUERCUS; Quercus hypoleucoides; REDUCTION EN PATE; Trees; Wood
• ISSN: 0099-2240; 1098-5336
• DOI: 10.1128/aem.61.1.138-144.1995

The effects of incubation time and temperature on the ability of isolates of the chlamydosporic and thermophilic fungus Ganoderma colossum (Fr.) C. F. Baker to cause selective delignification of Quercus hypoleucoides A. Camus were evaluated by standard in vitro agar block tests. Chemical and scanning electron microscopy studies of decayed wood were used to determine the extent of selective delignification or simultaneous decay caused by each fungal isolate. At 35 degrees C, the percent weight loss increased from 6.1% after 4 weeks to a maximum of 32.5 to 33.0% after 16 and 20 weeks of incubation. The average percent Klason lignin-chlorite holocellulose ratios (PKL/CHC) decreased from 0.35 in the control wood block to 0.22 in wood blocks incubated for 12 weeks; this indicated selective delignification. The average PKL/CHC increased for the 16-and 20-week incubation periods, indicating greater removal of polysaccharides during longer incubation periods. In temperature studies, the percent weight loss after 12 weeks was 26 to 27% between 30 and 40 degrees C and less than 16% for the 25 and 45 degrees C treatments. The average PKL/CHC ranged from 0.18 to 0.16 between 35 and 40 degrees C, whereas they were 0.23 and 0.31 for the 25 and 45 degrees C treatments, respectively. Scanning electron microscopy confirmed an optimum temperature range near 35 to 40 degrees C and incubation times of 8 to 12 weeks for selective delignification. Under these conditions, ray parenchyma, fiber tracheids, and vessels were devoid of middle lamella; pit regions of cells were visible with significantly enlarged apertures; and individual cells were separated and clearly delimited. Extensive delignification of wood occurred throughout the wood blocks evaluated. Incubation times longer than 12 weeks resulted in greater degradation of wood cell walls and thus in greater removal of the polysaccharide component of the wood