Conjugated linoleic acid production by lactic acid bacteria

VAN NIEUWENHOVE, C.; GONZÁLEZ, S.; PÉRZ CHAIA, A.

Jaén, España

Congreso; Food Safety Under Extreme Conditions; 2004

Conjugated linoleic acid production by lactic acid bacteria Van Nieuwenhove1,2, C. P., González1,2, S. N. , Pérez Chaia1,2, A.B. 1 CERELA-CONICET, Chacabuco 145, Tucumán, Argentina; 2 Universidad Nacional de Tucumán, Ayacucho 479, Tucumán, Argentina. Corresponding author: vancarina@hotmail.com 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 automatic 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. termophilus). The selected strains were able to produce CLA in presence of high LA concentrations (1000 mg/ml), but the  major formation was obtained at 400 mg/ml 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. termophilus) or as adjunct 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. Key Words: conjugated linoleic acid, lactic acid bacteria, dairy bacteria