Pretreatment for cellulose hydrolysis by carbon dioxide explosion

Cellulosic materials were treated with supercritical carbon dioxide to incr ease the reactivity of cellulose, thereby to enhance the rate and the exten t of cellulose hydrolysis. In this pretreatment process, the cellulosic mat erials such as Avicel, recycled paper mix, sugarcane bagasse and the repulp ing waste of recycled paper are placed in a reactor under pressurized carbo n dioxide at 35 degrees C for a controlled time period. Upon an explosive r elease of the carbon dioxide pressure, the disruption of the cellulosic str ucture increases the accessible surface area of the cellulosic substrate to enzymatic hydrolysis. Results indicate that supercritical carbon dioxide i s effective for pretreatment of cellulose. An increase in pressure facilita tes the faster penetration of carbon dioxide molecules into the crystalline structures, thus more glucose is produced from cellulosic materials after the explosion as compared to those without the pretreatment. This explosion pretreatment enhances the rate of cellulosic material hydrolysis as well a s increases glucose yield by as much as 50%. Results from the simultaneous saccharification and fermentation tests also show the increase in the avail able carbon source from the cellulosic materials for fermentation to produc e ethanol. As an alternative method, this supercritical carbon dioxide expl osion has a possibility to reduce expense compared with ammonia explosion, and since it is operated at the low temperature, it will not cause degradat ion of sugars such as these treated with steam explosion due to the high-te mperature involved.