PRODUCTION OF CONJUGATED LINOLEIC-ACID BY DAIRY STARTER CULTURES

Nineteen different strains of lactobacilli, lactococci, streptococci a nd propionibacteria commonly used as dairy starter cultures were teste d for their ability to produce conjugated linoleic acid (CLA) from fre e linoleic acid in vitro. Two strains of Propionibacterium freudenreic hii ssp. freudenreichii and one strain of P. freudenreichii sp. sheram nii were found to be capable of converting free linoleic acid to extra cellular CLA. The highest level of CLA formed in the media was 265 mu g ml(-1). Of the different isomers, cis- and trans-9,11-octadecadienoi c acid represented more than 70% of the total CLA formed. The inhibito ry effect of linoleic acid on the growth of the bacteria and its conve rsion to CLA in different media by propionibacteria are discussed.