Abstract
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.