Characterization of Palo Podrido, a Natural Process of Delignification in Wood
Characterization of Palo Podrido, a Natural Process of Delignification in Wood
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Palo Podrido（木材脱木质素的自然过程）的表征
DOI：
10.1128/aem.56.1.65-74.1990
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发表时间：
1990
影响因子：
4.4
通讯作者：
Pedro Muga
中科院分区：
文献类型：
--
作者：
E. Agosin;R. Blanchette;H. Silva;C. Lapierre;K. Cease;R. Ibach;A. Abad;Pedro Muga
研究了智利南部温带森林中发现的广泛脱木素木材Palo podrido的初期到晚期的化学和形态变化，以及其他类型的白腐病腐烂。Palo podrido是对木质素的选择性或非选择性去除的白色腐烂的总称，而Palo Blanco描述的是具有高级脱木素阶段的白色腐烂木材。选择性脱木素主要发生在桉树和红木的树干上，它们的木素含量最低，其木素的β-芳基醚键最多，丁香基/愈创木基比最高。一种灵芝是与腐烂有关的主要白腐真菌。用硫代酸解方法研究了木质素在白腐病降解过程中的结构变化，结果表明β-芳基醚连接的丁香基单元比愈创木基单元更有针对性地降解，特别是在选择性脱木素的情况下。超微结构研究表明，脱木素过程弥漫在整个细胞壁。木质素首先从离管腔最近的次生壁去除，然后穿过次生壁向中间薄板移动。中层和细胞角是最后降解的区域。在选择性脱木素的一些(但不是全部)样品中发现了黑色锰矿。在脱木素的高级阶段，可以找到几乎纯的纤维素，尽管聚合度降低。纤维素酶似乎是解聚的原因。在未漂白的纸浆中，木素选择性脱木素可获得较高的白度和较好的打浆能力。然而，其低粘度导致纸浆的阻力性能较差。降解的最后阶段(即富含纤维素的次生壁层的分解)导致形成胶状物质。该物质的超微结构和化学分析表明，基质没有木质细胞壁的微纤维结构特征，但仍含有丰富的葡聚糖。
Chemical and morphological changes of incipient to advanced stages of palo podrido, an extensively delignified wood, and other types of white rot decay found in the temperate forests of southern Chile were investigated. Palo podrido is a general term for white rot decay that is either selective or nonselective for the removal of lignin, whereas palo blanco describes the white decayed wood that has advanced stages of delignification. Selective delignification occurs mainly in trunks of Eucryphia cordifolia and Nothofagus dombeyi, which have the lowest lignin content and whose lignins have the largest amount of β-aryl ether bonds and the highest syringyl/guaiacyl ratio of all the native woods included in this study. A Ganoderma species was the main white rot fungus associated with the decay. The structural changes in lignin during the white rot degradation were examined by thioacidolysis, which revealed that the β-aryl ether-linked syringyl units were more specifically degraded than the guaiacyl ones, particularly in the case of selective delignification. Ultrastructural studies showed that the delignification process was diffuse throughout the cell wall. Lignin was first removed from the secondary wall nearest the lumen and then throughout the secondary wall toward the middle lamella. The middle lamella and cell corners were the last areas to be degraded. Black manganese deposits were found in some, but not all, selectively delignified samples. In advanced stages of delignification, almost pure cellulose could be found, although with a reduced degree of polymerization. Cellulolytic enzymes appeared to be responsible for depolymerization. A high brightness and an easy refining capacity were found in an unbleached pulp made from selectively delignified N. dombeyi wood. Its low viscosity, however, resulted in poor resistance properties of the pulp. The last stage of degradation (i.e., decomposition of cellulose-rich secondary wall layers) resulted in a gelatinlike substance. Ultrastructural and chemical analyses of this substance showed the matrix to have no microfibrillar structure characteristic of woody cell walls but to still be rich in glucan.