乳酸球菌在食品工業上利用的很多，而在生產過程中能分泌出大量欲表現的蛋白，是大家希望得到的結果，因此我們利用併列啟動子nisR promoter接上nisA promoter來增強表現量，以nisI 作為測試指標，可看到併列啟動子PnisR-PnisA比起單一Promoter PnisA ，有較高的nisin resistence 。另一方面，PnisA在乳酸球菌MG1363並不一定能以galactose 和lactose增強表現，反而會加以抑制。因此原本以外泌訊息序列（Signal peptide usp45）接上lipid-free nisI的蛋白，但其分泌至液態培養基的蛋白表現量不足以SDS-PAGE偵測到。

Lactococcus lactis is frequently used in food production. It will be a great benefit to us, if Lactococcus lactis can produce large amount of wanted proteins, and secrete them into the medium. We use tandem promoter (PnisR, PnisA) to enhance the expression of nisI. PnisR-PnisA-nisI showed higher nisin resistence than PnisA-nisI did. PnisA can not be induced by galactose and lactose in lactococcus lactis MG1363. In fact, galactose and lactose may inhibit PnisA in high concentration of nisin. We fused signal sequence usp45 to lipid-free nisI, which could secrete into medium, but neither PnisR-PnisA or PnisA is strong enough to express more proteins, according to the result of SDS-PAGE.

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