Optimization of culture conditions and characterization of inulinase of ethanol-producing Kluyveromyces marxianus Y1

Jerusasalem artichoke was used as a carbohydrate raw material to produce fuel ethanol.A yeast strain of Kluyveromyces marxianus Y1 was selected for ethanol production using Jerusasalem artichoke by one step process.The optimum condition for extra cellular inulinase production by Kluyveromyces marxianus Y1 was as follows(in g/L) : inulin(40),yeast extract(4),peptone(4),urea(1).Fermentation medium pH 5.0,and cultivation temperature 30 ℃.The agitation rate at 150 r/min was optimal for enzyme production(54 U/mL) with a fermetation time of 120 h in shake flask.The optimum reaction parameters of the inulinase production were 55 ℃,pH 5.0.The enzyme also showed good temperature adaptability and stability at pH=4.6～5.2.The activity ratio of the inulinase toward inulin and the sucrose was 1.7 and 8% ethanol did not affect the activity of the inulinase.