Arai Tsutomu, Biely Peter, Uhliariková Iveta, Sato Nobuaki, Makishima Satoshi, Mizuno Masahiro, Nozaki Kouichi, Kaneko Satoshi, Amano Yoshihiko
Department of Chemistry and Material Engineering, Faculty of Engineering, Shinshu University, 4-17-1 Wakasato, Nagano 380-8553, Japan.
Institute of Chemistry, Slovak Academy of Sciences, Dúbravská Cesta 9, 845 38 Bratislava, Slovak Republic.
J Biosci Bioeng. 2019 Feb;127(2):222-230. doi: 10.1016/j.jbiosc.2018.07.016. Epub 2018 Aug 22.
Hydrothermal reaction is known to be one of the most efficient procedures to extract hemicelluloses from lignocellulosic biomass. We investigated the molecular structure of xylooligosaccharides released from corn cob in a continuous flow type hydrothermal reactor designed in our group. The fraction precipitable from the extract with four volumes of ethanol was examined by H-NMR spectroscopy and MALDI-TOF MS before and after enzymatic treatment with different purified enzymes. The released water-soluble hemicellulose was found to correspond to a mixture of wide degree of polymerization range of acetylarabinoglucuronoxylan fragments (further as corn cob xylan abbreviated CX). Analysis of enzymatic hydrolyzates of CX with an acetylxylan esterase, GH3 β-xylosidase, GH10 and GH11 xylanases revealed that the main chain contains unsubstituted regions mixed with regions of xylopyranosyl residues partially acetylated and occasionally substituted by 4-O-methyl-d-glucuronic acid and arabinofuranose esterified with ferulic or coumaric acid. Single 2- and 3-O-acetylation was accompanied by 2,3-di-O-acetylation and 3-O-acetylation of Xylp residues substituted with MeGlcA. Most of the non-esterified arabinofuranose side residues were lost during the hydrodynamic process. Despite reduced branching, the acetylation and ferulic acid modification of pentose residues contribute to high yields and high solubility of the extracted CX. It is also shown that different enzyme treatments of CX may lead to various types of xylooligosaccharides of different biomedical potential.
水热反应是从木质纤维素生物质中提取半纤维素最有效的方法之一。我们在本课题组设计的连续流动式水热反应器中，研究了从玉米芯中释放出的低聚木糖的分子结构。在用不同纯化酶进行酶处理前后，通过H-NMR光谱和MALDI-TOF MS对用四倍体积乙醇从提取物中沉淀出的部分进行了检测。发现释放出的水溶性半纤维素对应于乙酰阿拉伯糖基葡萄糖醛酸木聚糖片段（以下简称为玉米芯木聚糖，CX）的聚合度范围较宽的混合物。用乙酰木聚糖酯酶、GH3β-木糖苷酶、GH10和GH11木聚糖酶对CX的酶水解产物进行分析表明，主链包含未取代区域，与部分乙酰化且偶尔被4-O-甲基-D-葡萄糖醛酸取代的吡喃木糖残基区域以及被阿魏酸或香豆酸酯化的阿拉伯呋喃糖混合。单个2-O-和3-O-乙酰化伴随着被MeGlcA取代的Xylp残基的2,3-二-O-乙酰化和3-O-乙酰化。大多数未酯化的阿拉伯呋喃糖侧链残基在流体动力学过程中丢失。尽管支链减少，但戊糖残基的乙酰化和阿魏酸修饰有助于提高提取的CX的产率和溶解度。还表明，对CX进行不同的酶处理可能会产生具有不同生物医学潜力的各种类型的低聚木糖。
