Study On Enzymatic Hydrolysis Of Steam-exploded Corn Stalk In Condition Of Mechanical Agitation

Energy crisis and environmental problems have driven the development of renewable energy in China. Having rich sources and ecological benefit, the cellulose fuel ethanol is considered as the best liquid altermative fuel and becomes the hot spot for industrial technology research. The process route of cellulose fuel ethanol has been proved feasible, but agitator as the key equipment of production process has not yet been researched specially. By studying the process of cellulose enzymatic hydrolysis, the experiment is meant to improve the conversion rate, reduce energy consumption and decrease the production cost by optimizing the enzymatic hydrolysis condition and the equipment.The corn stalk pretreated by steam-exploded method is used as raw material. Firstly, single factor experiments are taken to optimize the enzymatic hydrolysis condition with the sugar concentration as the survey index, taking general economic factors and technical feasibility into consideration. The best enzymatic hydrolysis occurs when substrate without crushing, temperature at50℃, substrate concentration at15%(w/w), enzyme concentration60IU/(g substrate) and without Tween20.Secondly, the rheological property is studied and the experiment data of the suspension of corn stalk pretreated by steam-exploded method can be described by Power Law models, the R2is more than0.98. Furthermore, the viscosity of suspension shows the time-dependent property.Thirdly, the amplification experiment is taken to study the sugar concentration and viscosity change of enzymatic hydrolysis process in7L fermentor with dual six flat blade disk turbine agitator. The results suggest that the viscosity of enzymolysis hydrolysate become smaller with the enzymatic reaction going, but the sugar concentration become higher and the enzymatic hydrolysis process can be divided in four phases. In order to improve the substrate concentration so as to improve the sugar concentration of enzymatic hydrolysate, fed-batch methods are used in experiments. By comparing the different ways of feeding, the results suggest that three fed-batch method is a better way for enzymatic hydrolysis process.According to the range of variation of the apparent viscosity in enzymatic hydrolysis process, some agitators are desighed and optimized. The best condition is using type A of four-pitched-blade T shape agitator with the rotate speed at1OOr/min. By studying the enzymatic hydrolysis process of high substrate concentration, it suggests that comparing to one fed-batch method, the conversion rate of three fed-batch mathod is a little smaller, but the energy consumpution and the requirement of equipment are clearly lower.At last, the changes of solid substrate in enzymatic hydrolysis process are studied by biological microscope, laser scattering particle size distribution analysis (LSPSDA), X-ray diffraction(XRD), scanning electron microscope(SEM). The results show that the particle size of solid particles are becoming lower, the specific surface area becomes larger gradually, the crystallinity and the crystallite size become smaller and the internal holes increase.