The gene appA for phytase from Escherchia coli was modified by means of site directed mutagenesis to improve its thermal stability. Using yeast expression system the mutant phytase appA-2QN produced in shaking-flask culture showed an increased thermal stability. To increase its expression level and lower production costs,an approach of the high cell-density fermentation of recombinant yeast GS115/appA-2QN was carried out in this study. During fermentation the concentration of glycerin was controlled to promote the cell growth and achieve the high cell-density fermentation. The method of chromotropic acid spectrophotography was used to determine the concentra-tion of methanol during fermentation. The results showed that the OD600nm of the cell reached 313 after 147 h fermen-tation in a 5 L fermentor. After inducing of 102 h with methanol at a concentration of 2. 5%,the expression level of phytase reached 7. 06 g/L. The phytase activity was 2. 03 × 105 U/mL. These results indicated that the cell density and the expression level of target protein were significantly improved by high density fermentation. The recombinant yeast strain has favorable expression stability.%对来源于大肠杆菌的植酸酶基因 appA进行突变获得植酸酶基因突变体 appA-2QN，利用酵母表达系统在摇瓶培养条件下表达后，该植酸酶突变体显示出良好的热稳定性。为提高该植酸酶的表达量，降低植酸酶的生产成本，对表达该酶的重组酵母菌 GS115/appA-2QN进行了高密度发酵研究，通过控制发酵过程中碳源（甘油）的添加使得菌体生长达到一定密度，从而实现高效表达。在诱导蛋白质表达阶段，发酵液中甲醇的含量影响植酸酶的表达量，利用变色酸分光光度法对甲醇含量进行了检测分析。结果表明，在5 L 发酵罐中进行高密度发酵147 h 后，菌体浓度OD600nm达到313，通过将甲醇浓度控制在2.5%左右，经过诱导102 h后，蛋白达到了较高的表达量，为7.06 g/L，酶活性（发酵效价）为2.03×105 U/mL。结果表明，通过高密度发酵提高了产植酸酶 appA-2QN 的酵母工程菌的细胞生长密度和蛋白质表达量，揭示该重组酵母菌株具有良好的表达稳定性。
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