Study On The Production Of Cellulosic Ethanol By Enzymatic Hydrolysis Of Kitchen Waste

Cellulosic ethanol is a green energy that can replace fossil fuels.As a populous country,China has a huge annual output of kitchen waste,which contains abundant cellulosic biomass and is an important raw material for the production of Cellulosic ethanol.However,due to the structural characteristics of cellulose biomass,it is difficult to be directly degraded and utilized,and it needs to be pre-treated before enzymatic fermentation.At present,the pretreatment of cellulosic biomass has the problems of low efficiency and high cost,and the unstable environment of cellulase restricts the large-scale preparation of Cellulosic ethanol.Therefore,this project uses ultrasound assisted Na OH method to pretreat cellulose biomass in kitchen waste,and studies the effect of ultrasound assisted Na OH pretreatment on the structural damage of cellulose biomass and the efficiency of enzymatic hydrolysis for sugar production;The method of enzyme immobilization was used to improve the environmental stability of cellulase,and the simultaneous saccharification and fermentation process of free cellulase and immobilized cellulase to produce Cellulosic ethanol was optimized using cellulose biomass in kitchen waste as raw material.The main research content and results are as follows:（1）A single factor experiment was conducted to investigate the effects of Na OH concentration,treatment temperature,ultrasound time,and ultrasound power on the pretreatment of cellulose biomass from kitchen waste.Based on this,a response surface experiment was designed,and the results showed that the optimal process conditions for pre-treatment of cellulose biomass from kitchen waste were:Na OH concentration of 10%,treatment temperature of 72.5℃,ultrasonic time of 30 minutes,and ultrasonic power of 200W.Through experiments,it can be concluded that ultrasound assisted promotion of the contact between Na OH and lignin can effectively improve the efficiency of Na OH in removing lignin,and the yield of glucose can be increased by 30%.Fourier transform infrared spectroscopy was used to analyze the materials before and after treatment,and the absorption peaks related to lignin were significantly weakened,indicating that lignin was effectively removed and the enzymatic hydrolysis efficiency was improved.（2）The effects of sodium alginate concentration,Ca Cl₂ concentration,immobilization time and the amount of magnetic nano Fe₃O₄ particles on the immobilized cellulase were studied by single factor experiment.On this basis,an orthogonal experiment was designed,and the results showed that the optimal preparation conditions were as follows:the concentration of sodium alginate was 4%,the concentration of Ca Cl₂was 5%,the immobilization time was 3 hours,the amount of magnetic nano Fe₃O₄ particles was 50 mg/ml,and the glucose concentration after the enzymatic hydrolysis of kitchen waste cellulose biomass by immobilized cellulase was 1.05 mg/m L.The carrier was analyzed by Fourier transform infrared spectroscopy,Scanning electron microscope and magnetic properties.The results showed that cellulase was successfully immobilized on the carrier that magnetic nano-Fe₃O₄ particles combined with sodium alginate and gelatin.The experiment proved that the carrier could be recycled by magnets to achieve the purpose of reuse.（3）Using free cellulase and activated Saccharomyces cerevisiae,the effects of cellulase dosage,Saccharomyces cerevisiae dosage,p H and fermentation temperature on Cellulosic ethanol production by simultaneous saccharification and fermentation were studied through single factor experiments.On this basis,the orthogonal experiment was designed to optimize the technological conditions for simultaneous saccharification and fermentation of Cellulosic ethanol.The results showed that the optimal technological conditions were:cellulase 30 mg,Saccharomyces cerevisiae 10 m L,initial p H=5,fermentation temperature 45℃.After 72hours of fermentation,the ethanol concentration reached 6.43 mg/m L.（4）The technological conditions of simultaneous saccharification and fermentation of pretreated kitchen waste cellulose biomass to produce Cellulosic ethanol were optimized by using immobilized cellulase.At the same time,the fermentation process of immobilized cellulase was compared with that of free cellulase,and it was found that the p H and fermentation temperature of immobilized cellulase were broader than those of free cellulase.Meanwhile,after 5 cycles of use,the ethanol concentration of immobilized cellulase after synchronous saccharification and fermentation process remained at 70%after the first use.The experimental results indicate that immobilized cellulase can be recycled multiple times,so immobilized cellulase is superior to free cellulase in terms of usage conditions.The results of this study indicate that ultrasound assisted Na OH pretreatment of cellulose biomass from kitchen waste can effectively improve the efficiency of enzymatic hydrolysis and sugar production.At the same time,immobilized cellulase has good application prospects in synchronous saccharification and fermentation processes,providing a certain theoretical basis for achieving efficient and green resource utilization of kitchen waste.