| The strains of cellulose degradation and ethanol fermentation were screened out, respectively, and the process of fermentation was researched with corn straw as raw maerial.Firstly, the crushed corn straw was pretreated with sodium hydroxide and ammonia water.Secondly, the solide residue from pretreatment was degraded with the crude enzyme from cellulose-producing strain.Then,the mixture of saccharifrcation liqud and hyrolysate was detoxified and concentrated.The last, the process optimization for fuel ethanol production from xylose and glucose by yeast M-3 were studied. The main results were as follows:(1) Two ways pretreatment of sodium hydroxide and ammonia water showed that 4% sodium hydroxide solution to be the best of the conversion rate of reducing sugar was 44.22% .The conversion of pretreatment was 7.74%,the conversion of enzymatic hydrolysis was 36.48%.(2) A high cellulase-producing and xylanase-producing fungus Z-7 was isolated using the methods of transparent zone, filter paper degradation and shaking culture. The optimal enzyme-producing conditions of the fungus Z-7 were as follows: the optimum quantity of inoculation 3%, medium volume 50mL, pH 5.5, temperature 38°C and cultivation for 48 hours. The activities of CMC-Na enzyme and xylanase were as high as 1000U·mL-1 and 126.6U·mL-1 under the optimal enzyme-producing conditions, respectively.(3) Crude enzyme which was made by Z-7, to degrade residue from pretreatment shows the optimal decolorization were as follows: enzyme added 250 U/g, pH4.8, substrate concentration 200g/L, temperature 50°C.,the reducing sugar concentration reached to 41.68% and the conversion of substrate is 48.63% under these conditions.(4) Among the seven yeast which can ferment xylose and glucose simultaneously, M-3 was more capable of producing ethanol than other strain. And the yeast was identified as Candidasp by its morphology and physiological characteristics.(5) The optimal fermentation conditions of M-3 on xylose were as follows: initial sugar concentration 60g/L, 30°C, pH4.5, and the rotational speed of oscillator 70 r/min;and the final ethanol concentration was 6.1g/L,and the rate of the sugar to ethanol was 30.5%.The optimal conditions of converted mixture of xylose and glucose liquid to fuel ethanol as follows: the ratio of glucose to xylose was 2, pH5, 34°C ,the rotation speed was70r/min, under such a condition..The final ethanol concentration was 23.0g/L, and the conversion of the sugar transfer to ethanol was 38.3%.The final ethanol concentration was 20.47g/L, the conversion of the sugar transfer to ethanol was 0.359g/g in the solution of hydrolyzed cornmeal at 72 hours. |
