一步法发酵菊芋产乙醇菌种的筛选及产酶条件、酶学性质的研究

从腐烂的菊芋及实验室保存的菌种中，选育到一株发酵菊芋产乙醇的菌株克鲁维酵母Kluyveromyces marxianus Y1。利用正交实验法对克鲁维酵母产菊粉酶的培养基组成及培养条件进行优化，确定培养基组成（g/L）为：菊粉40，酵母粉4，蛋白胨4，尿素1；初始pH5．0，温度30℃，150r／min条件下培养达到最佳产酶效果（57U／mL）。该菌株所产菊粉酶的性质测定结果表明：以菊粉为底物，该菊粉酶最适反应温度为55℃，在60℃以下稳定性很好，高于60℃时酶迅速失活；最适pH为5．0，pH4．6—5．2范围内酶稳定性很好；该酶属于外切型菊粉酶，体积分数为8％的乙醇对酶活力基本没有影响。

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.