In situ production of conjugated linoleic acid by Bifidobacterium lactis BB12 and Lactobacillus acidophilus LA5 in milk model medium

In this study, the fermentation conditions for in situ production of conjugated linoleic acid (CLA) by Bifidobacterium lactis BB12 and Lactobacillus acidophilus LA5 in a milk model medium were optimized. Box–Behnken and combined designs were implemented to find a predictive model for the in situ bioconversion of CLA by pure B. lactis BB12, L. acidophilus LA5, as well as their co-culture. The results showed that under optimal conditions, CLA biosynthesized by B. lactis BB12 and L. acidophilus LA5 are 110.03 ± 4.58 μg/ml and 82.42 ± 3.66 μg/ml, respectively. The functional groups of the produced CLA were also analyzed by Fourier-transform infrared spectroscopy, which confirmed the typical characteristics of long-chain fatty acids. Gas chromatography–mass spectrometry analysis further showed that both isomers of CLA (cis-9, trans-11 and trans-10, cis-12) were biosynthesized by B. lactis BB12 and L. acidophilus LA5 in supplemented cheese whey. This study indicated the most important factors affecting the fermentation bioprocess for biosynthesis of CLA by B. lactis BB12 and L. acidophilus LA5 in a low-cost food-grade medium. The findings of this study also showed that pure B. lactis BB12 and L. acidophilus LA5 have a good ability to produce bioactive CLA, but the co-culture of these two commercial probiotics have no synergistic effect on biosynthesis of CLA. •Conjugated linoleic acid was produced by Bifidobacterium lactis BB12 and Lactobacillus acidophilus LA5.•The most significant variables for in situ production of conjugated linoleic acid were obtained.•The predictive models of conjugated linoleic acid biosynthesis by pure and mixed cultures were developed.•The mixed culture showed no advantage to conjugated linoleic acid biosynthesis in comparison with their pure cultures.