Fig. 3. Sugar yields after 24 h of CO 2 -pressurized enzymatic saccharification of CaCCO-treated rice straw powder.
All reactions including Ca(OH) 2 pretreatment, CO 2 neutralization, and enzymatic saccharification were carried out in the 96 mL pressure-resistant glass tube "Hiper Glass Cylinder (HGC)" (HPG-96-3; Taiatsu Techno Corp.). One gram of fine-powdered rice straw, 100 mg of Ca(OH) 2 , and 18 mL of water in the HGC were well mixed and heated at 120 °C for 1 h. After cooling, CO 2 was injected into the HGC at a pressure of 0.5 MPa and settled at room temperature overnight to complete neutralization of the slurry. Then, 1 mL of the same enzyme mixture in Fig. 2 was added to the neutralized slurry in the HGC, followed by pressurization of CO 2 up to the desired partial pressure. Saccharification reactions were performed at 50 °C for 24 h and the amounts of liberated monosaccharides and solubilized sugars were measured in the same way as for Fig. 2.