Ionic liquids (ILs) are widely used for biomass pretreatment because of their excellent dissolving capacity. The efficient and economical use of ILs in pretreatment greatly depends on revealing the underlying mechanism of biomass dissolution. Here, we observed that cellulose microfibrils of rice straw swelled in ILs using atomic force microscopy, and the swelling resulted in a decrease in cellulose crystallinity as determined by time-course X-ray diffraction analysis. The swelling of the IL-induced cellulose microfibrils greatly promoted the saccharification efficiency of rice straw. Compared with conventional acid or alkali solutions, strong hydrogen bond interactions between ILs of the appropriate size and polysaccharides resulted in cellulose microfibrils swelling in ILs, which was demonstrated by nuclear magnetic resonance and molecular simulation. Therefore, microfibril swelling is the key step in cellulose dissolution with ILs; effective swelling could accelerate cellulose dissolution and biomass pretreatment. Thus, those results are helpful in understanding the mechanism of lignocellulose dissolution in ILs and developing new ILs for biomass pretreatment.

中文翻译：

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离子液体中微原纤维肿胀和溶解的纳米尺度观察

离子液体（ILs）由于其出色的溶解能力而被广泛用于生物质预处理。IL在预处理中的有效和经济使用在很大程度上取决于揭示生物质溶解的潜在机制。在这里，我们观察到稻草的纤维素微纤维使用原子力显微镜在ILs中溶胀，溶胀导致纤维素结晶度降低，这是通过时程X射线衍射分析确定的。IL诱导的纤维素微纤维的溶胀极大地提高了稻草的糖化效率。与常规的酸或碱溶液相比，适当大小的IL与多糖之间强烈的氢键相互作用导致纤维素微纤维在IL中膨胀，核磁共振和分子模拟证明了这一点。因此，微纤维的溶胀是用IL溶解纤维素的关键步骤。有效的溶胀可以加速纤维素的溶解和生物质的预处理。因此，这些结果有助于理解木质素在IL中的溶解机理，并为生物质预处理开发新的IL。