The present invention relates to a process for the production of conjugated linoleic acid and a process for the production of triglycerides with an increased content of conjugated linoleic acid. Moreover, the invention relates to a nucleic acid sequence; a nucleic acid construct, a vector and transgenic organisms comprising at least one nucleic acid sequence or one nucleic acid construct which encodes a polypeptide with conjugated linoleic isomerase activity. Furthermore, the invention relates to the use of a microorganism of the genus Bifidobacterium as a probiotic.