Sugarcane processing roughly generates 54 million tonnes sugarcane bagasse (SCB)/year, making SCB an important material for upgrading to value-added molecules. In this study, an integrated scheme was developed for separating xylan, lignin and cellulose, followed by production of xylo-oligosaccharides (XOS) from SCB. Xylan extraction conditions were screened in: (1) single extractions in NaOH (0.25, 0.5, or 1 M), 121 °C (1 bar), 30 and 60 min; (2) 3 × repeated extraction cycles in NaOH (1 or 2 M), 121 °C (1 bar), 30 and 60 min or (3) pressurized liquid extractions (PLE), 100 bar, at low alkalinity (0–0.1 M NaOH) in the time and temperature range 10–30 min and 50–150 °C. Higher concentration of alkali (2 M NaOH) increased the xylan yield and resulted in higher apparent molecular weight of the xylan polymer (212 kDa using 1 and 2 M NaOH, vs 47 kDa using 0.5 M NaOH), but decreased the substituent sugar content. Repeated extraction at 2 M NaOH, 121 °C, 60 min solubilized both xylan (85.6% of the SCB xylan), and lignin (84.1% of the lignin), and left cellulose of high purity (95.8%) in the residuals. Solubilized xylan was separated from lignin by precipitation, and a polymer with β-1,4-linked xylose backbone substituted by arabinose and glucuronic acids was confirmed by FT-IR and monosaccharide analysis. XOS yield in subsequent hydrolysis by endo-xylanases (from glycoside hydrolase family 10 or 11) was dependent on extraction conditions, and was highest using xylan extracted by 0.5 M NaOH, (42.3%, using Xyn10A from Bacillus halodurans), with xylobiose and xylotriose as main products. The present study shows successful separation of SCB xylan, lignin, and cellulose. High concentration of alkali, resulted in xylan with lower degree of substitution (especially reduced arabinosylation), while high pressure (using PLE), released more lignin than xylan. Enzymatic hydrolysis was more efficient using xylan extracted at lower alkaline strength and less efficient using xylan obtained by PLE and 2 M NaOH, which may be a consequence of polymer aggregation, via remaining lignin interactions.

中文翻译：

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甘蔗渣阿拉伯木聚糖的提取，结合酶法生产低聚木糖和分离纤维素

甘蔗加工大约每年产生 5400 万吨甘蔗渣 (SCB)，使 SCB 成为升级为增值分子的重要材料。在本研究中，开发了一种用于分离木聚糖、木质素和纤维素的综合方案，然后从 SCB 生产低聚木糖 (XOS)。木聚糖提取条件筛选如下：(1) NaOH 单次提取（0.25、0.5 或 1 M），121 °C (1 bar)，30 和 60 分钟；(2) 在 NaOH（1 或 2 M）中进行 3 次重复萃取循环，121 °C (1 bar)，30 和 60 分钟或 (3) 加压液体萃取 (PLE)，100 bar，低碱度 (0–0.1 M NaOH) 在 10–30 分钟和 50–150 °C 的时间和温度范围内。较高浓度的碱 (2 M NaOH) 增加了木聚糖产量，并导致木聚糖聚合物的表观分子量更高（使用 1 和 2 M NaOH 时为 212 kDa，与使用 0.5 M NaOH 的 47 kDa 相比），但降低了取代糖含量。在 2 M NaOH、121 °C、60 分钟的条件下重复提取木聚糖（SCB 木聚糖的 85.6%）和木质素（木质素的 84.1%），并在残留物中留下高纯度的纤维素 (95.8%)。通过沉淀将溶解的木聚糖与木质素分离，并通过 FT-IR 和单糖分析证实了一种聚合物，其具有被阿拉伯糖和葡萄糖醛酸取代的 β-1,4-连接的木糖主链。内切木聚糖酶（来自糖苷水解酶家族 10 或 11）的后续水解中的 XOS 产量取决于提取条件，并且使用 0.5 M NaOH 提取的木聚糖最高（42.3%，使用来自 Bacillus halodurans 的 Xyn10A）以及木二糖和木三糖作为主要产品。本研究显示 SCB 木聚糖、木质素和纤维素的成功分离。高浓度的碱会导致木聚糖的取代度较低（尤其是减少的阿拉伯糖基化），而高压（使用 PLE）会比木聚糖释放更多的木质素。酶促水解使用在较低碱性强度下提取的木聚糖效率更高，而使用 PLE 和 2 M NaOH 获得的木聚糖效率较低，这可能是聚合物聚集的结果，通过剩余的木质素相互作用。