Reasons for the differences in biotransformation of conjugated linoleic acid by Lactobacillus plantarum.

Conjugated linoleic acid (CLA) has attracted a great deal of attention for its functions in weight loss, regulation of metabolism, and antioxidant capabilities. Many microorganisms, including rumen bacteria, propionic acid bacilli, and Lactobacillus, have CLA biotransformation ability. The CLA production capability of different species is different, as are those different strains of the same species. However, the reasons for this discrepancy remain unclear. In this study, 14 strains of Lactobacillus plantarum were found, through gas chromatography-mass spectrometry analysis, to be capable of converting linoleic acid to CLA. The transcriptional levels of CLA-related genes in the high- (AR195, WCFS1, and AR488) and low-yield strains (AR176, AR269, and AR611) were analyzed using real-time quantitative PCR. The transcriptional levels of cla-hy, cla-dh, and cla-dc in AR195 were the lowest in the exponential phase, but it had the highest CLA yield. Correlation analysis showed no correlation between CLA yield and the transcription level of these genes in the exponential phase. The results showed that a high transcriptional level in the exponential phase of cla-hy, cla-dh, and cla-dc did not necessarily lead to high CLA production. Investigation of the transcription level in different growth phases showed that the CLA biotransformation abilities of Lactobacillus plantarum strains significantly depended on the transcriptional maintenance of cla-hy, cla-dh, and cla-dc. We observed a correlation between CLA production and increased levels of cla-hy transcription, but a prerequisite is needed: the transcription of cla-dh and cla-dc should be upregulated and maintained a high transcriptional level during the platform period. This study provides a new strategy for screening high CLA-producing strains. It also lays a theoretical foundation for regulating CLA biotransformation and increasing the yield of CLA.