近年來食品工業趨向減少防腐劑之使用，而改用乳酸菌或酵素來達到保存食品的目的，因此乳酸菌對於冷藏食品腐敗或病原菌抑制方面之探討倍受重視。聯乙醯（diacetyl）為乳酸菌代謝過程中的一種芳香性產物，具有香味，且已被證實在乳酸菌中具有抑菌的效果。過去的研究也指出，增加乳酸菌中ilvBN基因的表現，可以有效的增加乳酸菌中聯乙醯的產量。因此，本研究將利用實驗室所分離出的新菌種Lactobacillus rhamnosus TCELL-1以overlapping PCR方法夾出這段酵素基因，選用適當的穿梭載體（pHY300PLK），再透過電穿孔（electroporation）的方式將完整的基因放進Lb. rhamnosus TCELL-1。由GC/MS的結果顯示，在有大量表現ilvBN基因的乳酸菌株中，其聯乙醯的產量增為原來的四倍。而利用延遲洋菜圓點分析法作抑菌的測試，對有害菌有明顯抑制的效果。

In recent year food industry trend to reduce the using of preservative, and change to use lactic acid bacteria or enzyme to preserved food, so we could go a step further to raise its additional value. Diacetyl is one kind of aromatic product in the metabolic process of lactic acid bacteria, which has the fragrance and also has inhibition effect to some bacteria. According to the past research, overexpression of ilvBN gene in lactic acid bacteria may effectively increase diacetyl of lactic acid bacteria. Therefore, this research we will isolate the enzymatic gene from a new strain Lactobacillus rhamnosus TCELL-1 by overlapping PCR method, ligated with a shuttle vector pHY300PLK via electroporation into Lb. rhamnosus TCELL-1. The results of GC/MS show that the encoding ilvBN gene is overexpressive and has been observed higher production about four fold of diacetyl than without the enzymatic gene does in Lb. rhamnosus TCELL-1. In deferred agar spot assay, we observed that overexpression ilvBN gene in TCELL-1 can inhibit food pathogens effectively.

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