高产菊粉酶酵母筛选、发酵和酶学性质研究

筛选到1株菊粉酶高产克鲁维酵母菌株，采用酵母高密度细胞发酵方法，最高菊粉酶产量达到288.78u/mL,比80～90年代国际上报道的克鲁维酵母菊粉酶最高产量高6.8倍。该酶的菊粉酶/转化酶活性比为1/24.72；菊糖m=13.3mmol/L,蔗糖Km=62.6mmol/L；最适反应pH值为4.4，但在pH3.8～5.6的范围内均保持了较高的活性，相当于最适pH值下活性的90%；最适反应温度为55℃，在50～575℃范围内能够保持较高活性，50℃下酶的半衰期约为16h；外加Mg2+提高酶活性11.28%。

A Study on Screening and High Density Cell Cultivation of A Yeast Strain Kluyveromyces with High Inulinase Yielding and Its Enzymology Properties

A yeast strain Kluyveromyces with high inulinase yield was screened. The highest inulinase activity of 288.78 u/mL was reached when a high cell density cultivation method was developed for inulinase production. It was 6.8 times higher than the highest level reported in the same species. The activity ratio of its inulinase to invertase was 1/24.72, the Km values were 13.3 mmol/L and 62.6 mmol/L when inulin and sucrose were used as substrate, respectively; The optimum pH value was 4.4, this enzyme also showed a good pH adaptability and stability, i.e. more 90% of the highest level was maintained between pH 3.8 and 5.6; The optimum reaction temperature was 55 degrees C, higher activity was maintained between 50-57.5 degrees C, its half life period was 16 hours at 55 degrees C; It was found for the first time that addition of magnesium ion into the reaction system increased the enzyme activity by 11%.