本研究以基因重組Eshrechia coli.BL21(DE3)/(pET43.1a)生產白細胞介素-20( interleukin-20 )，此蛋白質可用於乾癬(psoriasis)之治療研究。研究發現此菌株最適生長溫度為42oC，不適合在鹼性條件下生長，溶氧值維持在20%以上即已足夠菌體之生長。在同一生長溫度下誘導之最佳溫度為37oC。在生長溫度為42oC下操作，並改變其誘導後之溫度，所得最高目標蛋白質濃度為相當於BSA 0.42 g/L。降低生長溫度為37OC，菌體濃度雖僅能達14.3 g/L，但目標蛋白質產量卻可達0.89 g/L ﹔實驗後發現生長溫度37OC之蛋白質分解酵素產生較42oC少，而等量之蛋白質分解酵素在本實驗所改變的誘導溫度範圍內活性差不多，故推測蛋白質分解酵素是降低生長溫度後蛋白質產量提高之主因。本菌株亦可添加乳糖誘導，實驗發現，添加10 g/L乳糖誘導，目標蛋白質產量極微小，若添加20 g/L乳糖誘導則目標蛋白質產量可達1.135 g/L，比產率為0.05 g/g cell比利用IPTG誘導之比產率(0.062 g/g cell)略低。經電泳分析發現本菌株在此研究系統中有包涵體的產生，勢必也會對蛋白質產量造成影響。

　　The present research used a recombinant strain, Escherichia coli BL21(DE3)/(PET43.1a),to produce interleukin-20 which can be used to treat and study with pso-riasis. With this research we found that the most suitable temperature for the growth of this strain is 42oC, and it can’t grow well in basic condition ,and the DO 20% is enough for the growth of the srtain.37oC is the best temperature for production at the same growth temperature. With the 42oC growth temperature, the highest protein concentration it can reach is 0.42 g/L. When we lower the growth temperature to 37oC,in spite of cell density 14.3 g/L, the target protein concentration can rise to 0.898 g/L. At this study, the protease concentration is higher at 42oC growth temperature than 37oC, and the protease activity is about the same within all the production temperature range. According to the above result, the main reason for the rise of the target protein concentration is the protease concentration. This strain can also be induced with lactose. After batch fermentation, we found that 10 g/L lactose is not enough for this strain to express significant amount of target protein. When we used 20 g/L lactose for induction, 1.135 g/L of our target protein can be produced. And its specific productivity is 0.05 g/g cell, which is a little lower than the value 0.062g/g cell achieved when induced with 1 mM IPTG. It will affect the production of our target protein that this strain can produce inclusion body .

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