Studies On Engineering Of Basidiomycetous-Alkaline Pretreatments On Corn Straw

With the development of the energy, foodstuff and environment crisis, the study on utilization of lignocellulose for ethanol production is significant. This thesis studied on biological and chemical pretreatment on corn straw, enzymatic hydrolysis of pretreated one for reducing sugars production and ethanol fermention.Since it is hard for cellulase to access cellulose in lignocellulose, different type of white- & brown-rot fugal pretreatments combined with pretreatment of 1.76 g/L NaOH, 0.9% H2O2, 20 g/L substrate were evaluated firstly. The results indicated that Hyrophous sp.69 pretreated for 15 days could achieve the best effect with yields of reducing sugars of 0.430 g/g(corn straw) at 50 FPU/g cellulase loading (71.7% of theoretical), which was 34.9% higher than that obtained without fungal pretreatment.Seconedly, the chemical pretreatment assistanted was optimized. Eight ways of chemical pretreatments'compare proved that NaOH/H2O2 could be the best chemical reagent for assistant pretreatment. Furthermore, the engineering parameters of NaOH/H2O2 pretreatment on corn straw pretreated by Hyrophous sp.69 for 15 days were optimized. The results proved that the best conditions for that was 7 g/L NaOH, 0.7% H2O2 and 50 g/L substrate for 24 hours, which could release 0.447 g reducing sugars from 1 g corn straw on 50 FPU cellulase loading, and was equal to 74.5% of theoretical.After pretreatments of corn straw, Cellulase loading, reaction time, temperature, rotate speed, pH and substrate concentration for enzymatic hydrolysis were optimized by response surface design, as well as the effect of tween-80 on enzymatic hydrolysis. The results proved that 30 FPU/g cellulase loading, 20 g/L substrate, pH 4.8, 200 r/min and 49℃for 48 hours could be the most effective and economic way for enzymatic hydrolysis, under which the yields of reducing sugars achieved 0.477 g/g corn straw on 30 FPU cellulase loading (79.6% of theoretical). Compared to the single A/O pretreated ones, the amount of reducing sugars released increased by 44.7%.Two-step fermention & simultaneous saccharification and fermentation (SSF) of fungal-chemical pretreated corn straw were optimized. The results indicated that ethanol yield of fungal-chemical pretreated corn straw by two-step fermention was 40.5% higher than that of the single chemical pretreated one under its best conditions. The ethanol yield of fungal-chemical pretreated corn straw by SSF was 17.0% higher than that of the single chemical pretreated one under the best fermention conditions.All the results above were meaningful not only in academic research,but also in utilization of renewable lignocellulosic biomass, decreasing the cost of fuel ethanol from lignocellulose, and alleviating the world's grain crisis.