Department of Chemical Engineering, Auburn University, Auburn, AL 36849-5127, USA.
Bioresour Technol. 2010 Feb;101(4):1337-47. doi: 10.1016/j.biortech.2009.09.035. Epub 2009 Oct 8.
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.
微晶纤维素 (MCC) 经亚临界水预处理，以提高其与纤维素酶的酶反应性。纤维素/水悬浮液与亚临界水（即加压加热）混合，然后送入保持恒温恒压的反应器中。反应后，产物立即在双管热交换器中冷却。产物的固体部分（即处理后的 MCC）被分离并测试其分子结构和酶反应性。实验在 200 至 315 摄氏度、27.6 MPa 和 3.4-6.2 秒反应时间的范围内进行。通过粘度法对处理后的 MCC 的聚合度 (DP(v)) 进行表征，通过 X 射线衍射 (XRD) 对结晶度进行表征。此外，还进行了差示扫描量热法和扫描电子显微镜 (SEM) 分析，以研究纤维素结构的任何变化。不出所料，随着预处理温度的升高，纤维素的 DP(v) 稳步下降，在 300 摄氏度以上迅速下降。另一方面，XRD 分析表明预处理后结晶度没有降低，但在 300 摄氏度处理的 MCC 中注意到纤维素 I-II 结构的部分转化。在所有处理样品的 SEM 图像中都观察到表面裂缝和沟槽的发展。在 > 或 = 300 摄氏度的处理后，酶反应性增加。
