Investigation On Production Of Fuel Ethanol With Jerusalem Artichoke By Simultaneous Sacchrification And Fermentation

Jerusalem artichoke was a perennial herbaceous plant which was resistant to drought and grows in the desert, barren hills and other soil conditions. Jerusalem artichoke can be cultivated easily and its yield was high (3-5 tons / acre).So it was a highly potential non-grain crops. Jerusalem Artichoke mainly contained inulin which was accounting for about 80% of its dry weight. Inulin was composed of linear chains of D-fructose units. Inulin can be hydrolyzed into fructose by inulinase,and fructose can be directly used to produce ethanol by yeast. The production of fuel ethanol with Jerusalem Artichoke is the new approach of fuel ethanol industry.At present, there are two methods for fuel ethanol fermentation with Jerusalem artichoke,which are Separate hydrolysate and fermentation and Simultaneous saccharification and fermentation. Comparing with separate hydrolysate and fermentation,one strain and one step fermentation can be realized in Simultaneous saccharification and fermentation. The fermentation process can be predigested and it can also save the costs of culturing seed. So there were lots of advantages.In order to screen high inulinase activity and high ethanol fermentation capability strain,in this work,inulinase activity of 6 Saccharomyces cerevisiae(31009,31133,1446,1416,1575,)were measured. And ethanol fermentation capability of 6 strain were compared.The results show that the inulinase activity of S cerevisiae Angel and its ethanol concentration were highest,11.46 U/mL,50.38 g/L respectively. The inulinase activity and capability of ethanol fermentation were related.As the low inulinase activity of S.cerevisiae Angel,it can not meet the requirements of industrial production.Therefore,mutation and screening were required.Yeast strains for ethanol fermentation with inulin as carbon source was screened from its parent yeast strain'Angel'by ultraviolet mutaiton and microwave mutation together.Finally,a mutant yeast strain Y05 with higher inulinase activity was obtained. The inulinase activity of Y05 was up to 90.97 U/ml, which was about as 8 times as that of its parent yeast strain. Its higher capacity for producing inulinase and ethnaol remained stable after subculture for many times.Y05 was selected for ethanol production by means of simultaneous saccharification and fermentation in Jerusalem artichoke juice. The optimal fermentation condition was that:inulin concentration 20%(w/v),fermentation temperature 34℃,pH 4.0,inoculation 15%。There was no inhibition with high concentration of inulin. Method for seed preparation had significant influence on the ethanol fermentation. Adding 2% inulin into seed medium would help to produce enzyme.It was founded that corn plasm,(NH4)2SO4 stimulated ethanol fermentation significantly,while urea,NH4Cl inhibited fermentation. Adding fermentation promoter into the culture medium,biotin,Tween 20,oleic acid can enhance ethanol producing. Stearic acid inhibited fermentation. External saline ions also have been studied on the fermentation. Ca2+,Mg2+ promoted fermentation obviously,while I- inhibited producing ethanol significantly. The ethanol fermentation medium was that concentration of inulin 236.09 g/L,corn plasm 5.0 g / L,(NH4)2SO4 5.0 g/L,biotin 1.0×10-4 g/L,Tween 20 1.5 g/L,oleic acid 0.5 g/L,CaCl2 4.0×10-2 g/L,Na2SeO3 2.0×10-2 g/L. The fermentation condition was that temperature 34℃,pH 4.0,the concentration of carbon source in seed culture was 2%,inoculum 15%. In the end of fermentation,the final ethanol concentration of 93.41 g/L was achieved and ethanol yield was 0.415 g/g,total sugar utilization rate was 95.31 %,which were increased by 85.41 %,8.92 %,37.57 % respectively comparing with S.cerevisiae Angel.