Conjugated linoleic acid production by lactic acid bacteria

VAN NIEUWENHOVE, CARINA; GONZÁLEZ, SILVIA; PEREZ CHAIA, ADRIANA

Jaén - España

Congreso; FOOD SAFETY UNDER EXTREME CONDITIONS… a conference on small-scale production units of tradicional fermented foods; 2004

Conjugated linoleic acid (CLA) is a term used for a mixture of positional and geometric isomers of linoleic acid in which double bonds are conjugated. It is formed in rumen as an intermediary product during biohydrogenation. It is produced in many tissues too, like mammary gland, using vaccenic acid as substrate and represents over 78 % of total CLA present in milk. CLA has been reported to prevent carcinogenesis, atherosclerosis and modulate immune activity. Their presence in fat of ruminant, like milk and meat has a high health potential. Several strains have been probed to produce CLA from free linoleic acid (LA), and could be used to increase its content in dairy products. The aim of this work was to study some dairy bacteria, used in fermented products, to evaluate CLA production when LA is added to the medium. Eleven strains were screening in LAPTg or milk with linoleic acid addition. Lipids were extracted and methylated, and then authomatic injected in gas chromatographer. The results showed that the Propionibacteria used in our study were growth-inhibit by LA addition, and they could not form CLA. The four strains which had major conversion in LAPTg broth were selected for evaluate their CLA production in whole milk (L. casei, L. plantarum, Bifidobacterium and S. thermophilus). The selected strains were able to produce CLA in presence of high LA concentrations (1000 µg/ml), but the major formation was obtained at 400 µml of LA. All bacteria converted the major LA amount near the stationary phase. L. casei was the most LA-tolerant and produced CLA even at 800 µg/ml LA. This study showed that many lactic acid bacteria could form CLA, and thus increase it levels in fermented dairy products such as yogurt and cheeses. They may be used as starter cultures (i.e. L. casei, S.thermophilus) or as adjunct non-starter strains (i.e.L.plantarum, Bifidobacterium). Attention must be focused about specie, tolerance to LA and CLA conversion of each selected bacteria before to be used in dairy products elaboration. Keywords: conjugated linoleic acid, lactic acid bacteria, dairy bacteria.