Appl Environ Microbiol. 1995 Jan;61(1):138-44. 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 deg 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 deg C and less than 16% for the 25 and 45 deg C treatments. The average PKL/CHC ranged from 0.18 to 0.16 between 35 and 40 deg C, whereas they were 0.23 and 0.31 for the 25 and 45 deg C treatments, respectively. Scanning electron microscopy confirmed an optimum temperature range near 35 to 40 deg 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. For incubation times of 4 weeks or a temperature of 25 deg C, limited to no degradation of cells was observed. At 45 deg C, walls of fiber tracheids were eroded and ray parenchymal cells were extensively degraded, indicating that simultaneous degradation of cell walls occurred. Thus, the incubation temperature influenced the type of decay by G. colossum observed on oak wood blocks: extensive selective delignification at 35 to 40 deg C after more than 8 weeks of incubation or simultaneous decay at 45 deg C with 14% weight loss after 12 weeks of incubation. Isolates of G. colossum may prove useful in studies on mechanisms of delignification and biotechnological applications (e.g., biopulping) of lignin-degrading fungi.
采用标准的体外琼脂块试验，评估了培养时间和温度对温热型灵芝（Ganoderma colossum (Fr.) C. F. Baker）分生孢子选择性降解栓皮栎木质素能力的影响。对腐朽木材的化学和扫描电子显微镜研究用于确定每种真菌分离物引起的选择性降解或同时降解的程度。在 35°C 下，培养 4 周后，重量损失百分比从 6.1%增加到 16 周和 20 周时的最大 32.5%至 33.0%。平均凯氏木质素-氯仿全纤维素比（PKL/CHC）从对照木块的 0.35 下降到 12 周培养木块的 0.22，表明了选择性降解。在 16 周和 20 周的培养期间，PKL/CHC 增加，表明在较长的培养期间去除了更多的多糖。在温度研究中，在 30°C 至 40°C 之间，12 周后重量损失百分比为 26%至 27%，25°C 和 45°C 处理的重量损失百分比小于 16%。在 35°C 至 40°C 之间，PKL/CHC 的平均值为 0.18 至 0.16，而在 25°C 和 45°C 处理中，它们分别为 0.23 和 0.31。扫描电子显微镜证实，选择性降解的最佳温度范围接近 35°C 至 40°C，最佳孵育时间为 8 至 12 周。在这些条件下，射线薄壁组织、纤维管胞和脉管系统没有中层；细胞的凹陷区域可见明显扩大的孔；并且单个细胞被分离并清晰地限定。评估的木块中整个木材都发生了广泛的木质素降解。孵育时间超过 12 周会导致细胞壁的降解加剧，从而导致更多的木材多糖成分被去除。对于 4 周的孵育时间或 25°C 的温度，观察到细胞没有明显降解。在 45°C 下，纤维管胞的细胞壁被侵蚀，射线薄壁组织细胞被广泛降解，表明细胞壁同时降解。因此，孵育温度影响了在橡木木块上观察到的灵芝的腐烂类型：在超过 8 周的孵育后，在 35°C 至 40°C 下发生广泛的选择性木质素降解，或者在 12 周的孵育后在 45°C 下发生同时降解，重量损失为 14%。灵芝的分离物可能在木质素降解真菌的脱木质素机制和生物技术应用（例如生物制浆）研究中证明有用。
