Cellulose pretreatment in subcritical water: effect of temperature on molecular structure and enzymatic reactivity.,Bioresource Technology |
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Cellulose pretreatment in subcritical water: effect of temperature on molecular structure and enzymatic reactivity.,Bioresource Technology
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Microcrystalline cellulose (MCC) was pretreated with subcritical water in a continuous flow reactor for enhancing its enzymatic reactivity with cellulase enzyme. Cellulose/water suspension was mixed with subcritical (i.e., pressurized and heated) water and then fed into the reactor maintained at a constant temperature and pressure. After the reaction, product was immediately cooled in a double-pipe heat exchanger. The solid portion of the product (i.e., treated MCC) was separated and tested for molecular structure and enzymatic reactivity. Experiments were conducted at temperatures ranging from 200 to 315 degrees C, at 27.6 MPa, and for 3.4-6.2 s reaction times. The treated MCC was characterized for degree of polymerization (DP(v)) by viscosimetry, and crystallinity by X-ray diffraction (XRD). In addition, differential scanning calorimetry and scanning electron microscopy (SEM) analyses were carried out to study any transformation in the cellulose structure. As expected, DP(v) of cellulose steadily decreased with increase in the pretreatment temperature, with a rapid drop occurring above 300 degrees C. On the other hand, XRD analysis did not show any decrease in crystallinity upon pretreatment but, partial transformation of celluloses I-II structure was noticed in the MCC treated at 300 degrees C. Development of surface cracks and trenches were observed in the SEM images for all the treated samples. Enzymatic reactivity was increased after the treatment at > or = 300 degrees C.
中文翻译：
在连续流动反应器中用亚临界水预处理微晶纤维素（MCC），以增强其与纤维素酶的酶反应性。将纤维素/水悬浮液与亚临界（即加压和加热）水混合，然后进料到反应器中，并保持恒定的温度和压力。反应后，将产物立即在双管热交换器中冷却。分离产物的固体部分（即，处理的MCC）并测试其分子结构和酶反应性。实验是在200至315摄氏度的温度，27.6 MPa的温度下进行的，反应时间为3.4-6.2 s。通过粘度测定法表征处理的MCC的聚合度（DP（v）），并通过X射线衍射（XRD）表征结晶度。此外，进行差示扫描量热法和扫描电子显微镜（SEM）分析以研究纤维素结构中的任何转变。不出所料，随着预处理温度的升高，纤维素的DP（v）稳定下降，而在300摄氏度以上时则迅速下降。另一方面，XRD分析并未显示出预处理后结晶度的任何下降，而是纤维素的部分转化在300℃下处理的MCC中观察到I-II结构。对于所有处理的样品，在SEM图像中观察到表面裂纹和沟槽的发展。在>或= 300摄氏度处理后，酶反应性增加。随着预处理温度的升高，纤维素的DP（v）稳定下降，高于300摄氏度时迅速下降。另一方面，XRD分析并未显示出预处理后结晶度的任何下降，而是纤维素I-II的部分转化在300℃下处理的MCC中观察到结构。在所有处理的样品的SEM图像中观察到表面裂纹和沟槽的发展。在>或= 300摄氏度处理后，酶反应性增加。随着预处理温度的升高，纤维素的DP（v）稳定下降，高于300摄氏度时迅速下降。另一方面，XRD分析并未显示出预处理后结晶度的任何下降，而是纤维素I-II的部分转化在300℃下处理的MCC中观察到结构。在所有处理的样品的SEM图像中观察到表面裂纹和沟槽的发展。在>或= 300摄氏度处理后，酶反应性增加。在所有处理过的样品的SEM图像中都观察到了表面裂纹和沟槽的发展。在>或= 300摄氏度处理后，酶反应性增加。在所有处理过的样品的SEM图像中都观察到了表面裂纹和沟槽的发展。在>或= 300摄氏度处理后，酶反应性增加。 |
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