Screening Of Yeast Strains For Ethanol Production From Jerusalem Artichoke And Studies Of Fermentation Process Parameters

Jerusalem Artichoke mainly contains inulin that is composed of linear chains of D-fructose units which can be easily hydrolyzed chemically or biochemically into fructose. Jerusalem Artichoke is a new alternative to grain crops such as corn and wheat that are currently used for fuel ethanol production in China.Inulin utilizing strain was screened from the soil which Jerusalem Artichoke was planted as well rotten chicory. By orthogonal experiment, optimum culture medium was determined as following: inuline 40 g·L^-1, urea 1 g·L^-1,peptone 4 g·L^-1, yeast extract 4 g·L^-1;The influential circumstances to Kluyveromyces was rotate speed>pH>temperature, and the optimum combination is temperature 30℃, 120 h, rotate speed 150 rpm, pH 5.0 with the activity 58U·ml^-1 which was 5.2 fold higher than before. The enzymatic properties of Kluyveromyces was studied: the optimum pH was 5.0 and stable in pH4.6⁵.2;the optimum temperature was 55℃, inulinase activity is stable when the temperature is lower than 60℃, the enzyme activity decreased when the temperature is higher than 60℃. K⁺, Fe²⁺, Mg²⁺, Ca²⁺ have no obviouse activating function, while Mn²⁺ displayed inhibition effect;the value of I/S is 1/1.7, which indicating that it is exo- inulinase. When preserved at 4℃, the inulinase activity decreased to 71.24 % after 5 d, 30.15 % after 7 d;when preserved at 30℃, the inulinase activity decreased to 28.54 % after 5 d, 16.33 % after 7 d. The highest inulinase activity of 70U·ml^-1 was obtained using organic culture medium in feed culture.A yeast strain of Kluyveromyces marxianus was selected for ethanol production by means of simultaneous saccharification and fermentation. The effects of temperature, initial pH of media, aeration rate and initial inulin concentration on the ethanol fermentation performances of Kluyveromyces marxianus were investigated. The optimum temperature and initial pH were 29℃ and 4.6, respectively. Aerobic culture stimulated the growth of yeast, while anaerobic condition faciliated ethanol production. When the initial concentration of inulin was 235 g·L^-1, the final ethanol concentration of 11.5 % (v/v) was achieved with anethanol yield of 0.44. It was shown that the relative size of the particles had little effect on the fermentation and ethanol production was achieved by K marxianus with the yield of 86.5% at the concentration of 200 g-L"1 inulin.