中文摘要：

以毕赤酵母人β干扰素表达体系为研究对象，考察与蛋白酶活性相关的营养和环境因素对外源蛋白hIFNβ-HAS表达／降解的影响。结果表明，pH、谷氨酸和EDTA是显著影响hIFNβ-HAS表达的3个因素。通过响应面分析得到hIFNβ-HAS表达的最优条件为pH5．5、谷氨酸0．18％、EDTA12mmol／L，目的蛋白表达量为24．46mg／L。发酵终产物的电泳结果表明：条件优化后，h1FNβ-HSA降解带明显变淡，说明营养和环境因素的优化一定程度上抑制了蛋白酶的活性，由此增加了目的蛋白的积累。

英文摘要：

The effect of nutrition and environmental factors related to protease activity on the expression and degradation of exogenous protein （IFN β-HAS） was investigated in Pichia pastoris expression system. The results suggested that pH, glutamic acid and EDTA were three key factors significantly affected the expression of IFN β-HAS. Moreover, the optimal condition was determined as pH 5.5, glutamic acid 0.18% and EDTA 12 mmol/L by response surface analysis of three factors and three levels. The production of IFN β-HSA reached 24.46 mg/L. The electrophoresis results of the final fermentation product showed that the degradation of IFNβ-HSA reduced significantly and the production of target protein increased due to the activity of protease was inhibited after the optimization of nutrition and environmental factors.