Optimization Of Fuel Ethanol Production Fermented Using Corn Stalk With Phanerochaete Chrysosporium And The Mutagenic For Obtaining High Ethanol Yield Strains

The rapid development of the economy makes energy issues become increasingly serious. Concerns about the rising price of oil leads to an urgent need to develop new substitute energy. There lies great interest of fuel ethanol owing to its sustainable and zero-omission characters. China’s fuel ethanol industry started late but developed rapidly,the latest development direction for fuel ethanol has been adjusted to use non-grain crops as the main raw material. Phanerochaete chrysosporium is a typical strain of white rot fungi, which has been widely used in the degradation of cellulose and lignin material. P. chrysosporium can degrade cellulose of straws,and ethanol is the main secondary metabolites in the process of cellulose degrading.This thesis focused on the conversion of cellulosic ethanol from straws with P. chrysosporium.The fermentation conditions of straws by submerged and solid cultivation of P. chrysosporium was optimized in this paper. Then the mutation breeding of P. chrysosporium was investigated. After verified by the ethanol production and hereditary stability,the alcohol dehydrogenase gene sequence of mutant strain Y2-5 was analyzed. The main achievements of the research were:(1) The most suitable optimum medium of straws by submerged cultivation with P. chrysosporium: straws 20 g/L, glucose 10 g/L,ammonium tartrate 2.4 g/L,Twain 80 0.4%,Named nutrient solution 1.(2) The most suitable fermentation condition of straws by liquid-state:10% of inoculation concentration liquid loading volume 50 m L /250 m L, initial p H 4.5, 180 r/min, 37 ℃ of the fermentation temperature, The highest ethanol yield by liquid-state fermentation reached 3.692g/L after 7-day cultivation,which is 1.63 times of that obtained under initial conditions.(3) The dilute acids pretreatment of 1%-H2SO4 solution is needed in the solid-state fermentation of straws with P. chrysosporium. After pretreatment the content of lignin and hemicellulose decreased significantly in straws, and the relative cellulose content increased by 35%.(4) The most suitable solid-state fermentation conditions of straws. The addition of nutrient solution 1 as the exogenous nutrient to keep the moisture content at 60%,and the proportion of straw and bran of 6:4. Under this conditions the ethanol yield goes up to 1.562 g/100 g DS after 11-day cultivation at 33℃.(5) The best exposure time of ultraviolet radiation is 180 s. Three induced strains was achieved which has outstanding dehydrogenase activity. The ethanol yield was increases by approximately 10% than the original strain.(6) The mutant strain Y2-5 has better hereditary stability. The ADH activity of Y2-5 reached to 210 U/L on day 8,approximately 12% higher than the original strain.(7) The mutant strain Y2-5 has a new NAD binding regions than the original strain which may cause the increase of the ethanol production.