Beijing Advanced Innovation Center for Tree Breeding by Molecular Design, Beijing Forestry University, Beijing, 100083, China; Beijing Key Laboratory of Lignocellulosic Chemistry, Beijing Forestry University, Beijing, 100083, China.
Beijing Key Laboratory of Lignocellulosic Chemistry, Beijing Forestry University, Beijing, 100083, China.
Carbohydr Polym. 2020 Jun 15;238:116212. doi: 10.1016/j.carbpol.2020.116212. Epub 2020 Mar 28.
In this study, the cellulose and hemicelluloses in heartwood, sapwood, and bark of E. urophylla × E. grandis were comprehensively investigated. The ultrastructural topochemistry of carbohydrates in cell walls was examined in situ by confocal Raman microscopy. Cellulose and alkali-extractable hemicelluloses samples were isolated from different tissues and comparatively characterized by compositional carbohydrate analyses, determination of molecular weights, FT-IR spectroscopy, and XRD and NMR techniques. It was found that among all of the samples, heartwood cellulose had the highest molecular weight as well as the lowest degree of crystallinity. Meanwhile the hemicelluloses in heartwood had higher xylose content, lower degree of branching, slightly lower molecular weights but narrower polydispersity than those in sapwood. The eucalyptus hemicelluloses mainly consisted of (1→4)-β--xylan backbone with glucuronic acid side chains. Furthermore, the hemicelluloses isolated from sapwood had a higher degree of substitution with terminal galactose than those isolated from heartwood and bark.
在这项研究中，对尾叶桉×巨桉的心材、边材和树皮中的纤维素和半纤维素进行了综合研究。通过共聚焦拉曼显微镜原位研究了细胞壁中碳水化合物的超微结构拓扑化学。从不同组织中分离出纤维素和可碱提取的半纤维素样品，并通过组成性碳水化合物分析、分子量测定、FT-IR 光谱、XRD 和 NMR 技术对其进行比较表征。结果发现，在所研究的所有样品中，心材纤维素的分子量最高，结晶度最低。同时，心材半纤维素的木糖含量较高，支化度较低，分子量略低，但多分散性较窄。桉树半纤维素主要由（1→4）-β--木聚糖主链和葡萄糖醛酸侧链组成。此外，从边材中分离出的半纤维素与从心材和树皮中分离出的半纤维素相比，具有更高取代度的末端半乳糖。
