Pretreatment Of Corn Cob With Inorganic Acid And Ethanol Production By Simoultanous Saccrification And Fermentation

Oil, coal and other traditional energy sources have become depleted and resultedin environmental pollution. Lignocellulosic biomass is a renewable, cheap,abundantly available resource, its bioconversion to fuel can solve the imminentenergy and environmental crisis, and it is very meaningful in the sustainingdevelopment of our society and economy. In this thesis, some key contents includedpretreatment, enzymatic hydrolysis and fermentation in bioethanol conversion fromcorn cob were studied.HNO₃, HCl and HNO₃/HCl （1:1） were used as catalyst to hydrolyze corn cob forsugar releasing. The results suggested that HCl could release more xylose from thecorn cob materials in less time than HNO₃, but it brought more inhibitor at the sametime. HNO₃pretreatment generated less furfural and more effective in removing liginbut it was costly and time-consuming. The combined use of HNO₃and HCl could notonly weaken the disadvantages formed by using dilute HNO₃and HCl individually,but also could achieve the same separation effect for corn cob. The results ofsimultaneous saccrification and fermentation experiments demonstrated that theethanol yield was increased from48.8%to61.9%after pretreatment, and thecorresponding ethanol concentration was increased from15.8g/L to38.1g/L, whichincreased about1.4times.Corn cob was hydrolyzed in the presence of HNO₃/HCl with different proportionsand the results indicated that the suitable proportion of HNO₃/HCl was1:1. Theeffects of reaction temperature, reaction time and solid loading on the hydrolysis wereinvestigated furtherly. The optimization conditions were obtained by usingOrthogonal experiment design, with the reaction temperature of120C, reaction timeof30min and solid loading of15%. Under these conditions, the xylose yield in liquidphase was81.1%with the corresponding xylose concentration of55.7g/L, thecontents of cellulose in remaining solid increased to63.4%, which was25.3%higherthan that of raw material.The producing bioethanol used carn cob has been performed by simultaneoussaccrification and fermentation. The effects of temperature, pH, enzyme concentrationand yeast concentration on fermentation process were investigated. The results showed that the suitable fermentation conditions were reaction temperature of37C，pH5.0, enzyme loading of30FPU/g substrate, yeast concentration of10%（w/v）,fermentation time of72h and with the solid loading of150g/L, the finalconcentration of ethanol was41.4g/L, which is76.8%of the theoretical yield.