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An efficient magnetic carbon-based solid acid treatment for corncob saccharification with high selectivity for xylose and enhanced enzymatic digestibility

Qi, Wei, Liu, Guifeng, He, Chao, Liu, Shuna, Lu, Si, Yue, Jun, Wang, Qiong, Wang, Zhongming, Yuan, Zhenhong, Hu, Jianhua
Green chemistry 2019 v.21 no.6 pp. 1292-1304
X-radiation, acid treatment, catalysts, catalytic activity, cell walls, cellulose, corn cobs, enzymatic hydrolysis, enzymes, glucose, green chemistry, hydrolysis, lignocellulose, macropores, magnetic materials, magnetism, microscopy, porosity, saccharification, surface area, xylose
An effective method for corncob saccharification was investigated over a magnetic carbon-based solid acid (MMCSA) catalyst in the aqueous phase. MMCSA was synthesized through a simple and inexpensive impregnation–carbonization–sulfonation process. Under the optimal reaction conditions (150 °C, 2 h, 0.5 g corncob, 0.5 g catalyst and 50 ml deionized water), 74.9% of xylose yield was directly obtained from corncob, with 91.7% cellulose retention in the residue. After the reaction, the MMCSA was easily separated from the residue using an external magnet and reused 4 times, showing its high stability and catalytic activity. The enzymatic digestibility of the pretreated residue reached 95.2%, with a total sugar yield of 90.4%. The morphological and structural properties of the natural and treated corncobs were analyzed primarily through 3D X-ray microscopy to characterize the cell wall thickness, porosity, and pore surface area distribution. The increase of macropores (pore surface areas >200 μm²) was beneficial for the accessibility of cellulose to cellulosic enzymes, so the enzymatic digestibility was enhanced immediately. Compared with other traditional hydrolysis methods, this two-step hydrolysis approach represents an environmentally friendly and sustainable saccharification of lignocellulose to produce xylose and glucose while achieving the same level of reaction efficiency.