自兼性厭氧菌Lactobacillus delbrueckii subsp. bulgaricus中分離出酵素萃取液，以硫酸氨進行鹽析作用後，經12kD透析膜透析後之萃取液在50 ℃，pH4.5、60與7.5 下，與亞麻油酸反應10分鐘，結果發現此一萃取液具亞麻油酸異構�t活性，能將亞麻油酸轉變成兩種共軛亞麻油酸異構物：c-9，t-11-/t-9，c-11- 與c-9,c-11-/c-10,c-12-octadecadienoate。在pH6.0時，經異構化反應生成之二種共軛亞麻油酸異構物含量最高，分別為28.47與10.42ug，顯示此亞麻油酸異構�t萃取液最適當之反應 pH 值為 6.0。 以含 100kD 透析膜之圓片超過濾技術分離此酵素萃取液後，發現大於 100kD 之收集液具酵素活性，且其活性顯著地比未經超過濾處理之萃取液為高。
Crude enzyme extract was isolated from Lactobacillus delbrueckii subsp. bulgaricus, followed by salting out with addition of ammonium sulfate and dialyzing with 12 kD dialysis tubing. After reacted with linoleic acid at 50 ℃ for 10 min, the activity of linoleic acid isomerase was observed, as evidenced by the formation of two conjugated linoleic acid isomers, c-9,t-11-t-9,c-11-and c-9,c-11-/c-10,c-12- octadecadienoate. The highest levels of conjugated linoleic acids were produced at treatment of pH6.0, as compared with those of pH 4.5 and 7.5, and the levels were 28.47 and 10.42 ug, respectively, indicating the optimal pH of 6.0 for linoleic acid isomerase. The enzyme extract was filtrated through a 100kD disc membrane by ultrafiltration and the activity of linoleic acid isomerase was observed in the filtrate of >100kD. Moreover, higher enzyme activity was detected in this treatment than in the enzyme extract without ultrafiltration.
