Division of Chemistry of Renewable Resources, Department of Chemistry, University of Natural Resources and Life Sciences, Konrad-Lorenz-Strasse 24, A-3430 Tulln, Austria.
Department of Bioproducts and Biosystems, School of Chemical Engineering, Aalto University, P.O. Box 16300, FI-00076 Aalto, Finland.
Molecules. 2018 Sep 1;23(9):2223. doi: 10.3390/molecules23092223.
The effect of ball milling expressed as the yield of milled wood lignin (MWL) on the structure and molar mass of crude milled wood lignin (MWLc) preparation is studied to better understand the process' fundamentals and find optimal conditions for MWL isolation (i.e., to obtain the most representative sample with minimal degradation). Softwood (loblolly pine) MWLc preparations with yields of 20⁻75% have been isolated and characterized based on their molar mass distribution (by Size Exclusion Chromatography (SEC)), hydroxyl groups of different types (P NMR), methoxyl groups (HS-ID GC-MS), and sugar composition (based on methanolysis). Classical MWL purification is not used to access the whole extracted lignin. The results indicate that lignin degradation during ball milling occurs predominantly in the high molar mass fraction and is less pronounced in the low molar mass fraction. This results in a significant decrease in the M and M of the extracted MWLc with an increase in the yield of MWLc, but has only a very subtle effect on the lignin structure if the yield of MWLc is kept below about 55%. Therefore, no tedious optimization of process variables is necessary to achieve the required MWLc yield in this range for structural studies of softwood MWL. The sugar composition shows higher amounts of pectin components in MWLs of low yields and higher amounts of glucan and mannan in high-yield MWLs, confirming that lignin extraction starts from the middle lamella in the earlier stages of MWL isolation, followed by lignin extraction from the secondary wall region.
研究了球磨对磨木木素（MWL）产率的影响，即磨碎木本木质素（MWLc）的结构和摩尔质量的影响，以更好地理解该过程的基础原理，并找到 MWL 分离的最佳条件（即获得具有最小降解的最具代表性的样品）。根据其摩尔质量分布（通过尺寸排阻色谱法（SEC））、不同类型的羟基（P NMR）、甲氧基（HS-ID GC-MS）和糖组成（基于甲醇解），已从软木（火炬松）MWLc 中分离出产率为 20-75%的 MWLc 并进行了表征。未使用经典的 MWL 纯化方法来获得整个提取的木质素。结果表明，球磨过程中木质素的降解主要发生在高摩尔质量部分，在低摩尔质量部分则不太明显。这导致提取的 MWLc 的 M 和 M 随着 MWLc 产率的增加而显著降低，但如果将 MWLc 的产率保持在 55%以下，则对木质素结构的影响非常细微。因此，在这个范围内，不需要对工艺变量进行繁琐的优化，就可以达到所需的 MWLc 产率，从而可以对软木 MWL 的结构进行研究。糖组成表明，低产率的 MWL 中果胶成分的含量较高，高产率的 MWL 中葡聚糖和甘露聚糖的含量较高，这证实了木质素提取从 MWL 分离的早期阶段从中层开始，然后从次生壁区域提取木质素。
