共軛亞麻油酸是擁有共軛雙鍵的十八碳二烯酸，因為其共軛雙鍵位於不同位置與幾何結構的改變而形成不同的同分異構物，其中又以cis-9, trans-11與trans-10, cis-12兩種異構物具有較佳的生物活性。近年來，由於共軛亞麻油酸被發現具有不同的生物功能，例如(1)避免動脈粥樣硬化的發生、(2)提升體內免疫系統的功能、(3)促進脂肪分解，減少體脂肪含量、(4)促進生長、(5)具有抗癌效果，所以在食品科學與醫藥界裡引起廣泛的注意。在文獻中，已經有許多研究利用不同的微生物來進行共軛亞麻油酸的生物合成。
本研究以提高共軛亞麻油酸的產量為目標，選用Lactobacillus reuteri ATCC 55739為生產菌株，將亞麻油酸異構化為共軛亞麻油酸，並進行培養基設計以及反應條件較適化的研究。經過碳源、氮源與金屬離子的較適化探討之後，選擇2 g/L sucrose和45 g/L corn steep liquor作為培養基的碳源與氮源，而且發現所選擇的金屬離子對於共軛亞麻油酸的產量並沒有顯著性的增加。當Lactobacillus reuteri培養12小時之後，會達到exponential phase的末期，並利用此時的培養液與100 mg/L的亞麻油酸攪拌混合，進行亞麻油酸的異構化反應。經過反應條件的較適化探討之後，在37°C的環境下，反應溶液裡添加500 mg/L的磷脂質，反應2小時之後，共軛亞麻油酸的產量為41.52 mg/L，較未改質前的培養基所得到的產量提升了5.08倍。

Conjugated linoleic acid (CLA) refers to a group of geometric and positional isomers of octadecadienoic acid with conjugated double bonds. Among the isomers, cis-9, trans-11 and trans-10, cis-12 octadecadienoic acids are the two major ones and have been suggested to be the most biologically active. In recent years, CLA has attracted much attention in food science and medicine because of its potential physiological functions. For example, it can avoid the incidence of atherosclerosis; enhance the function of the immune system; decrease the body fat content; be used as growth promoting factor; and have anticarcinogenic activities. Several microorganisms can be used in the biosynthesis of CLA.
This study concerns the design of a culture medium for the cultivation of Lactobacillus reuteri ATCC 55739 and identification of optimal reaction conditions of isomerization to promote higher CLA production. The carbon and nitrogen sources in the culture medium with 2 g/L sucrose and 45 g/L corn steep liquor were found to be optimal. There was no significant increase of CLA productivity in the presence of various metal ions, which were selected for this study. After 12 h of cultivation, when the cells had reached late exponential phase, the culture broth was mixed with 100 mg/L linoleic acid (LA) to carry out the isomerization of LA. The reaction conditions were optimized and 37°C and 500 mg/L phospholipids were found to be optimal. After 2 h, 41.52 mg/L of CLA was produced which was 5.08-fold higher than the productivity obtained by using Lactobacillus cultivated in a medium that is generally used.

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