Centre for Energy, Indian Institute of Technology Guwahati, Guwahati 781039, Assam, India.
Carbohydrate Enzyme Biotechnology Laboratory, Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, Guwahati 781039, Assam, India.
J Biosci Bioeng. 2021 Jun;131(6):647-654. doi: 10.1016/j.jbiosc.2021.01.009. Epub 2021 Mar 4.
Xylan is the major hemicellulose present in sugarcane stem secondary cell walls. Xylan is composed of xylose backbone with a high degree of substitutions, which affects its properties. In the present study, the xylan from sugarcane tops (SCT) was extracted and characterized. Compositional analysis of xylan extracted from SCT (SCTx) displayed the presence of 74% of d-xylose residues, 16% of d-glucuronic acid residues and 10% of l-arabinose. High performance size exclusion chromatographic analysis of SCTx displayed a single peak corresponding to a molecular mass of ∼57 kDa. The Fourier transform infrared spectroscopic analysis of SCTx displayed the peaks corresponding to those obtained from commercial xylan. FESEM analysis of SCTx showed the granular and porous surface structure. Differential thermogravimetric analysis (DTG) of SCTx displayed two thermal degradation temperatures (T) of 228°C, due to breakdown of the side chains of glucuronic acid and arabinose and 275°C, due to breakdown of xylan back bone. The presence of arabinose and glucuronic acid as a side chains was confirmed by the DTG and thermogravimetric analysis. The CHNS analysis of SCTx showed the presence of only carbon and hydrogen supporting its purity. The recombinant xylanase (CtXyn11A) from Clostridium thermocellum displayed a specific activity of 1394 ± 51 U/mg with SCTx, which was higher than those with commercial xylans. The thin layer chromatography and electrospray ionization mass spectroscopy analyses of CtXyn11A hydrolysed SCTx contained a series of linear xylo-oligosaccharides ranging from degree of polymerization 2-6 and no substituted xylo-oligosaccharides because of the endolytic activity of enzyme. The extracted xylan from SCT can be used as an alternative commercial substrate and for oligo-saccharide production.
木聚糖是甘蔗茎次生细胞壁中主要的半纤维素。木聚糖由木糖主链组成，具有高度的取代度，这影响了它的性质。本研究从甘蔗梢中提取并表征了木聚糖。从甘蔗梢中提取的木聚糖（SCTx）的组成分析显示，74%的木糖残基、16%的葡萄糖醛酸残基和 10%的阿拉伯糖残基。SCTx 的高性能尺寸排阻色谱分析显示出单一的峰，对应于约 57 kDa 的分子量。SCTx 的傅里叶变换红外光谱分析显示出与商业木聚糖获得的峰相对应。SCTx 的 FESEM 分析显示出颗粒状和多孔的表面结构。SCTx 的差示热重分析（DTG）显示出两个热降解温度（T），分别为 228°C，由于葡萄糖醛酸和阿拉伯糖的侧链断裂，和 275°C，由于木聚糖主链的断裂。阿拉伯糖和葡萄糖醛酸作为侧链的存在通过 DTG 和热重分析得到了证实。SCTx 的 CHNS 分析表明仅存在碳和氢，支持其纯度。来自嗜热梭菌的重组木聚糖酶（CtXyn11A）对 SCTx 的比活性为 1394±51 U/mg，高于对商业木聚糖的比活性。CtXyn11A 水解 SCTx 的薄层色谱和电喷雾电离质谱分析含有一系列从聚合度 2-6 的线性木二糖寡糖，由于酶的内切活性，没有取代的木二糖寡糖。从甘蔗梢中提取的木聚糖可作为商业替代底物和寡糖生产的来源。
