Application Of Microwave And Additives To The Pretreatment And Enzymatic Hydrolysis Of Plant Fiber Materials

Pretreatment and enzymatic hydrolysis are the two important steps of making fuel ethanol from plant fiber materials. As a heat-efficient and pollution-free energy, microwave can change the crystal structure of cellulose and increase the efficiency of enzymatic hydrolysis. Dilute acid and alkali pretreatment are common pretreatment methods. Therefore in this thesis microwave/sulfuric acid and microwave/sodium hydroxide are used in the pretreatment of corn stover in order to increase the efficiency of pretreatment and enzymatic hydrolysis. Tween20, Tween80, Mg2+ and Ca2+ are added to increase the sugar yield in enzymatic hydrolysis. The main results are as follows:1. Compared to microwave and sulfuric acid pretreatment singly, pretreatment by microwave/sulfuric acid can significantly enhance the removal efficiency of hemicellulose and increase the sugar yield in pretreatment and enzyme hydrolysis of corn stover. The best pretreatment conditions by microwave/sulfuric acid are temperature 190℃, sulfuric acid concentration 15 g/L, ratio of liquid to solid 30:1 and pretreatment time 3 min, under which the total sugar yield is 78.4 %.2. The best conditions for the enzymatic hydrolysis of corn ??er after pretreatment by microwave/sulfuric acid are enzyme loading 30 FPIU.g-1 substrate, temperature 50℃and pH 4.8. Microwave/sulfuric acid pretreatment can increase the generation rate of maximum reducing sugar and the total concentration of fermentable sugar.3. Compared to microwave and sodium hydroxide pretreatment singly, pretreatment by microwave/sodium hydroxide can significantly enhance the removal efficiency of lignin and increase the sugar yield in pretreatment and enzyme hydrolysis of corn stover. The best pretreatment conditions by microwave/ sodium hydroxide are temperature 130℃, sodium hydroxide concentration 15 g/L, pretreatment time 9 min and ratio of liquid to solid 30:1, under which the total sugar yield is 83.8 %.4. The best conditions for the enzymatic hydrolysis of corn stover after pretreatment by microwave/sodium hydroxide are enzyme loading 30 FPIU.g-1 substrate, pH 4.4 and temperature 50℃. Microwave/sodium hydroxide pretreatment can increase the generation rate of maximum reducing sugar and the total concentration of fermentable sugar.5. Appropriate concentration of Tween20, Tween80, Mg2+ and Ca2+ can also increase the sugar yield of enzyme hydrolysis of corn stover.