Conjugated linoleic acid synthesis by lactic acid bacteria cultured inskim milk

BARCAT MIRANDE A.; OLISZEWSKI R.; GONZÁLEZ S.N.; VAN NIEUWENHOVE CP.

S. M. de Tucumán

Congreso; VII Congreso Argentino de Migrobiología General SAMIGE del Bicentenario.; 2011

Sociedad Argentina de Microbiología

3.4 Conjugated linoleic acid synthesis by lactic acid bacteria cultured in skim milk [POSTER] Alvaro Barcat Mirande1, Rubén Oliszewski1,2 , Silvia N. González1,2 , Carina P. Van Nieuwenhove1,2 1 Universidad Nacional de Tucumán. Ayacucho 491, (4000) S.M. de Tucumán 2 CERELACONICET. Chacabuco 145, (4000) S. M. de Tucumán (carina@cerela.org.ar) Conjugated linoleic acid (CLA) is a biolipid with beneficial properties for humans, such as anticarcinogenic effect. Several authors have hypothesized that CLA production is a detoxification mechanism by which bacteria reduce the toxicity of free fatty acids. The aim of this study was to evaluate the CLA-synthesizing ability of lactic acid bacteria (LAB), using skim milk as culture medium and vegetal oils as substrate. Lactococcus lactis CRL 1434 and Lactobacillus paracasei CRL 575 were previously selected due to their high linoleic acid (LA) conversion rate observed in LAPTg and MRS medium, respectively. Strains were inoculated at 2 % (v/v) in 10 % (w/v) reconstituted skim milk. At regular intervals (0; 4; 8; 12; 18; 24 h), samples were taken to measure pH and growth (viable cell count). Lipid profile was determined at 24 h, by extracting lipid with chloroform/methanol solution (1:1, v/v) according to Folch et al. (1957). Fatty acids were derivatized following Chin et al. (1992) protocol, and analyzed by gaseous chromatography. Hydrolyzed soy and sunflower oils were individually added as substrate to obtain a final LA concentration of 200 and 400 μg/ml. Results showed that growth rate and pH values were not affected during the milk fermentation, with or without vegetal oil addition. After 24 h of incubation (37ºC) CLA production in L. paracasei CRL 575 culture was 58 and 65 μg/ml, when sunflower oil was added as substrate (200 and 400 μg/ml, respectively). Higher levels of CLA (69 and 74 μg/ml) were determined in skim milk supplemented with soy oil at the same concentrations. Lact. lactis CRL 1434 showed a similar behaviour in milk enriched with soy or sunflower oils. CLA production was 65 and 87 μg/ml in presence of sunflower oil (200 and 400 μg/ml, respectively), and 59 and 101 μg/ml when soy oil was added at the same concentrations. Both LAB strains showed a similar CLA production level in presence of hydrolyzed sunflower or soy oils, and a lower LA conversion rate than that previously observed in MRS or LAPTg broth. This fact could be due to the high protein concentration of milk which could neutralize the toxic effect of free fatty acids on bacteria metabolism. However, CLA concentration in fermented milk was higher when vegetal oils and LAB were used. This study demonstrates that LAB can be used as potential starter or adjunct cultures in the production of CLA-enriched milk. μg/ml in presence of sunflower oil (200 and 400 μg/ml, respectively), and 59 and 101 μg/ml when soy oil was added at the same concentrations. Both LAB strains showed a similar CLA production level in presence of hydrolyzed sunflower or soy oils, and a lower LA conversion rate than that previously observed in MRS or LAPTg broth. This fact could be due to the high protein concentration of milk which could neutralize the toxic effect of free fatty acids on bacteria metabolism. However, CLA concentration in fermented milk was higher when vegetal oils and LAB were used. This study demonstrates that LAB can be used as potential starter or adjunct cultures in the production of CLA-enriched milk. when soy oil was added at the same concentrations. Both LAB strains showed a similar CLA production level in presence of hydrolyzed sunflower or soy oils, and a lower LA conversion rate than that previously observed in MRS or LAPTg broth. This fact could be due to the high protein concentration of milk which could neutralize the toxic effect of free fatty acids on bacteria metabolism. However, CLA concentration in fermented milk was higher when vegetal oils and LAB were used. This study demonstrates that LAB can be used as potential starter or adjunct cultures in the production of CLA-enriched milk.1, Rubén Oliszewski1,2 , Silvia N. González1,2 , Carina P. Van Nieuwenhove1,2 1 Universidad Nacional de Tucumán. Ayacucho 491, (4000) S.M. de Tucumán 2 CERELACONICET. Chacabuco 145, (4000) S. M. de Tucumán (carina@cerela.org.ar) Conjugated linoleic acid (CLA) is a biolipid with beneficial properties for humans, such as anticarcinogenic effect. Several authors have hypothesized that CLA production is a detoxification mechanism by which bacteria reduce the toxicity of free fatty acids. The aim of this study was to evaluate the CLA-synthesizing ability of lactic acid bacteria (LAB), using skim milk as culture medium and vegetal oils as substrate. Lactococcus lactis CRL 1434 and Lactobacillus paracasei CRL 575 were previously selected due to their high linoleic acid (LA) conversion rate observed in LAPTg and MRS medium, respectively. Strains were inoculated at 2 % (v/v) in 10 % (w/v) reconstituted skim milk. At regular intervals (0; 4; 8; 12; 18; 24 h), samples were taken to measure pH and growth (viable cell count). Lipid profile was determined at 24 h, by extracting lipid with chloroform/methanol solution (1:1, v/v) according to Folch et al. (1957). Fatty acids were derivatized following Chin et al. (1992) protocol, and analyzed by gaseous chromatography. Hydrolyzed soy and sunflower oils were individually added as substrate to obtain a final LA concentration of 200 and 400 μg/ml. Results showed that growth rate and pH values were not affected during the milk fermentation, with or without vegetal oil addition. After 24 h of incubation (37ºC) CLA production in L. paracasei CRL 575 culture was 58 and 65 μg/ml, when sunflower oil was added as substrate (200 and 400 μg/ml, respectively). Higher levels of CLA (69 and 74 μg/ml) were determined in skim milk supplemented with soy oil at the same concentrations. Lact. lactis CRL 1434 showed a similar behaviour in milk enriched with soy or sunflower oils. CLA production was 65 and 87 μg/ml in presence of sunflower oil (200 and 400 μg/ml, respectively), and 59 and 101 μg/ml when soy oil was added at the same concentrations. Both LAB strains showed a similar CLA production level in presence of hydrolyzed sunflower or soy oils, and a lower LA conversion rate than that previously observed in MRS or LAPTg broth. This fact could be due to the high protein concentration of milk which could neutralize the toxic effect of free fatty acids on bacteria metabolism. However, CLA concentration in fermented milk was higher when vegetal oils and LAB were used. This study demonstrates that LAB can be used as potential starter or adjunct cultures in the production of CLA-enriched milk. μg/ml in presence of sunflower oil (200 and 400 μg/ml, respectively), and 59 and 101 μg/ml when soy oil was added at the same concentrations. Both LAB strains showed a similar CLA production level in presence of hydrolyzed sunflower or soy oils, and a lower LA conversion rate than that previously observed in MRS or LAPTg broth. This fact could be due to the high protein concentration of milk which could neutralize the toxic effect of free fatty acids on bacteria metabolism. However, CLA concentration in fermented milk was higher when vegetal oils and LAB were used. This study demonstrates that LAB can be used as potential starter or adjunct cultures in the production of CLA-enriched milk. when soy oil was added at the same concentrations. Both LAB strains showed a similar CLA production level in presence of hydrolyzed sunflower or soy oils, and a lower LA conversion rate than that previously observed in MRS or LAPTg broth. This fact could be due to the high protein concentration of milk which could neutralize the toxic effect of free fatty acids on bacteria metabolism. However, CLA concentration in fermented milk was higher when vegetal oils and LAB were used. This study demonstrates that LAB can be used as potential starter or adjunct cultures in the production of CLA-enriched milk.1,2 1 Universidad Nacional de Tucumán. Ayacucho 491, (4000) S.M. de Tucumán 2 CERELACONICET. Chacabuco 145, (4000) S. M. de Tucumán (carina@cerela.org.ar) Conjugated linoleic acid (CLA) is a biolipid with beneficial properties for humans, such as anticarcinogenic effect. Several authors have hypothesized that CLA production is a detoxification mechanism by which bacteria reduce the toxicity of free fatty acids. The aim of this study was to evaluate the CLA-synthesizing ability of lactic acid bacteria (LAB), using skim milk as culture medium and vegetal oils as substrate. Lactococcus lactis CRL 1434 and Lactobacillus paracasei CRL 575 were previously selected due to their high linoleic acid (LA) conversion rate observed in LAPTg and MRS medium, respectively. Strains were inoculated at 2 % (v/v) in 10 % (w/v) reconstituted skim milk. At regular intervals (0; 4; 8; 12; 18; 24 h), samples were taken to measure pH and growth (viable cell count). Lipid profile was determined at 24 h, by extracting lipid with chloroform/methanol solution (1:1, v/v) according to Folch et al. (1957). Fatty acids were derivatized following Chin et al. (1992) protocol, and analyzed by gaseous chromatography. Hydrolyzed soy and sunflower oils were individually added as substrate to obtain a final LA concentration of 200 and 400 μg/ml. Results showed that growth rate and pH values were not affected during the milk fermentation, with or without vegetal oil addition. After 24 h of incubation (37ºC) CLA production in L. paracasei CRL 575 culture was 58 and 65 μg/ml, when sunflower oil was added as substrate (200 and 400 μg/ml, respectively). Higher levels of CLA (69 and 74 μg/ml) were determined in skim milk supplemented with soy oil at the same concentrations. Lact. lactis CRL 1434 showed a similar behaviour in milk enriched with soy or sunflower oils. CLA production was 65 and 87 μg/ml in presence of sunflower oil (200 and 400 μg/ml, respectively), and 59 and 101 μg/ml when soy oil was added at the same concentrations. Both LAB strains showed a similar CLA production level in presence of hydrolyzed sunflower or soy oils, and a lower LA conversion rate than that previously observed in MRS or LAPTg broth. This fact could be due to the high protein concentration of milk which could neutralize the toxic effect of free fatty acids on bacteria metabolism. However, CLA concentration in fermented milk was higher when vegetal oils and LAB were used. This study demonstrates that LAB can be used as potential starter or adjunct cultures in the production of CLA-enriched milk. μg/ml in presence of sunflower oil (200 and 400 μg/ml, respectively), and 59 and 101 μg/ml when soy oil was added at the same concentrations. Both LAB strains showed a similar CLA production level in presence of hydrolyzed sunflower or soy oils, and a lower LA conversion rate than that previously observed in MRS or LAPTg broth. This fact could be due to the high protein concentration of milk which could neutralize the toxic effect of free fatty acids on bacteria metabolism. However, CLA concentration in fermented milk was higher when vegetal oils and LAB were used. This study demonstrates that LAB can be used as potential starter or adjunct cultures in the production of CLA-enriched milk. when soy oil was added at the same concentrations. Both LAB strains showed a similar CLA production level in presence of hydrolyzed sunflower or soy oils, and a lower LA conversion rate than that previously observed in MRS or LAPTg broth. This fact could be due to the high protein concentration of milk which could neutralize the toxic effect of free fatty acids on bacteria metabolism. However, CLA concentration in fermented milk was higher when vegetal oils and LAB were used. This study demonstrates that LAB can be used as potential starter or adjunct cultures in the production of CLA-enriched milk.Universidad Nacional de Tucumán. Ayacucho 491, (4000) S.M. de Tucumán 2 CERELACONICET. Chacabuco 145, (4000) S. M. de Tucumán (carina@cerela.org.ar) Conjugated linoleic acid (CLA) is a biolipid with beneficial properties for humans, such as anticarcinogenic effect. Several authors have hypothesized that CLA production is a detoxification mechanism by which bacteria reduce the toxicity of free fatty acids. The aim of this study was to evaluate the CLA-synthesizing ability of lactic acid bacteria (LAB), using skim milk as culture medium and vegetal oils as substrate. Lactococcus lactis CRL 1434 and Lactobacillus paracasei CRL 575 were previously selected due to their high linoleic acid (LA) conversion rate observed in LAPTg and MRS medium, respectively. Strains were inoculated at 2 % (v/v) in 10 % (w/v) reconstituted skim milk. At regular intervals (0; 4; 8; 12; 18; 24 h), samples were taken to measure pH and growth (viable cell count). Lipid profile was determined at 24 h, by extracting lipid with chloroform/methanol solution (1:1, v/v) according to Folch et al. (1957). Fatty acids were derivatized following Chin et al. (1992) protocol, and analyzed by gaseous chromatography. Hydrolyzed soy and sunflower oils were individually added as substrate to obtain a final LA concentration of 200 and 400 μg/ml. Results showed that growth rate and pH values were not affected during the milk fermentation, with or without vegetal oil addition. After 24 h of incubation (37ºC) CLA production in L. paracasei CRL 575 culture was 58 and 65 μg/ml, when sunflower oil was added as substrate (200 and 400 μg/ml, respectively). Higher levels of CLA (69 and 74 μg/ml) were determined in skim milk supplemented with soy oil at the same concentrations. Lact. lactis CRL 1434 showed a similar behaviour in milk enriched with soy or sunflower oils. CLA production was 65 and 87 μg/ml in presence of sunflower oil (200 and 400 μg/ml, respectively), and 59 and 101 μg/ml when soy oil was added at the same concentrations. Both LAB strains showed a similar CLA production level in presence of hydrolyzed sunflower or soy oils, and a lower LA conversion rate than that previously observed in MRS or LAPTg broth. This fact could be due to the high protein concentration of milk which could neutralize the toxic effect of free fatty acids on bacteria metabolism. However, CLA concentration in fermented milk was higher when vegetal oils and LAB were used. This study demonstrates that LAB can be used as potential starter or adjunct cultures in the production of CLA-enriched milk. μg/ml in presence of sunflower oil (200 and 400 μg/ml, respectively), and 59 and 101 μg/ml when soy oil was added at the same concentrations. Both LAB strains showed a similar CLA production level in presence of hydrolyzed sunflower or soy oils, and a lower LA conversion rate than that previously observed in MRS or LAPTg broth. This fact could be due to the high protein concentration of milk which could neutralize the toxic effect of free fatty acids on bacteria metabolism. However, CLA concentration in fermented milk was higher when vegetal oils and LAB were used. This study demonstrates that LAB can be used as potential starter or adjunct cultures in the production of CLA-enriched milk. when soy oil was added at the same concentrations. Both LAB strains showed a similar CLA production level in presence of hydrolyzed sunflower or soy oils, and a lower LA conversion rate than that previously observed in MRS or LAPTg broth. This fact could be due to the high protein concentration of milk which could neutralize the toxic effect of free fatty acids on bacteria metabolism. However, CLA concentration in fermented milk was higher when vegetal oils and LAB were used. This study demonstrates that LAB can be used as potential starter or adjunct cultures in the production of CLA-enriched milk.Lactococcus lactis CRL 1434 and Lactobacillus paracasei CRL 575 were previously selected due to their high linoleic acid (LA) conversion rate observed in LAPTg and MRS medium, respectively. Strains were inoculated at 2 % (v/v) in 10 % (w/v) reconstituted skim milk. At regular intervals (0; 4; 8; 12; 18; 24 h), samples were taken to measure pH and growth (viable cell count). Lipid profile was determined at 24 h, by extracting lipid with chloroform/methanol solution (1:1, v/v) according to Folch et al. (1957). Fatty acids were derivatized following Chin et al. (1992) protocol, and analyzed by gaseous chromatography. Hydrolyzed soy and sunflower oils were individually added as substrate to obtain a final LA concentration of 200 and 400 μg/ml. Results showed that growth rate and pH values were not affected during the milk fermentation, with or without vegetal oil addition. After 24 h of incubation (37ºC) CLA production in L. paracasei CRL 575 culture was 58 and 65 μg/ml, when sunflower oil was added as substrate (200 and 400 μg/ml, respectively). Higher levels of CLA (69 and 74 μg/ml) were determined in skim milk supplemented with soy oil at the same concentrations. Lact. lactis CRL 1434 showed a similar behaviour in milk enriched with soy or sunflower oils. CLA production was 65 and 87 μg/ml in presence of sunflower oil (200 and 400 μg/ml, respectively), and 59 and 101 μg/ml when soy oil was added at the same concentrations. Both LAB strains showed a similar CLA production level in presence of hydrolyzed sunflower or soy oils, and a lower LA conversion rate than that previously observed in MRS or LAPTg broth. This fact could be due to the high protein concentration of milk which could neutralize the toxic effect of free fatty acids on bacteria metabolism. However, CLA concentration in fermented milk was higher when vegetal oils and LAB were used. This study demonstrates that LAB can be used as potential starter or adjunct cultures in the production of CLA-enriched milk. μg/ml in presence of sunflower oil (200 and 400 μg/ml, respectively), and 59 and 101 μg/ml when soy oil was added at the same concentrations. Both LAB strains showed a similar CLA production level in presence of hydrolyzed sunflower or soy oils, and a lower LA conversion rate than that previously observed in MRS or LAPTg broth. This fact could be due to the high protein concentration of milk which could neutralize the toxic effect of free fatty acids on bacteria metabolism. However, CLA concentration in fermented milk was higher when vegetal oils and LAB were used. This study demonstrates that LAB can be used as potential starter or adjunct cultures in the production of CLA-enriched milk. when soy oil was added at the same concentrations. Both LAB strains showed a similar CLA production level in presence of hydrolyzed sunflower or soy oils, and a lower LA conversion rate than that previously observed in MRS or LAPTg broth. This fact could be due to the high protein concentration of milk which could neutralize the toxic effect of free fatty acids on bacteria metabolism. However, CLA concentration in fermented milk was higher when vegetal oils and LAB were used. This study demonstrates that LAB can be used as potential starter or adjunct cultures in the production of CLA-enriched milk.CRL 575 were previously selected due to their high linoleic acid (LA) conversion rate observed in LAPTg and MRS medium, respectively. Strains were inoculated at 2 % (v/v) in 10 % (w/v) reconstituted skim milk. At regular intervals (0; 4; 8; 12; 18; 24 h), samples were taken to measure pH and growth (viable cell count). Lipid profile was determined at 24 h, by extracting lipid with chloroform/methanol solution (1:1, v/v) according to Folch et al. (1957). Fatty acids were derivatized following Chin et al. (1992) protocol, and analyzed by gaseous chromatography. Hydrolyzed soy and sunflower oils were individually added as substrate to obtain a final LA concentration of 200 and 400 μg/ml. Results showed that growth rate and pH values were not affected during the milk fermentation, with or without vegetal oil addition. After 24 h of incubation (37ºC) CLA production in L. paracasei CRL 575 culture was 58 and 65 μg/ml, when sunflower oil was added as substrate (200 and 400 μg/ml, respectively). Higher levels of CLA (69 and 74 μg/ml) were determined in skim milk supplemented with soy oil at the same concentrations. Lact. lactis CRL 1434 showed a similar behaviour in milk enriched with soy or sunflower oils. CLA production was 65 and 87 μg/ml in presence of sunflower oil (200 and 400 μg/ml, respectively), and 59 and 101 μg/ml when soy oil was added at the same concentrations. Both LAB strains showed a similar CLA production level in presence of hydrolyzed sunflower or soy oils, and a lower LA conversion rate than that previously observed in MRS or LAPTg broth. This fact could be due to the high protein concentration of milk which could neutralize the toxic effect of free fatty acids on bacteria metabolism. However, CLA concentration in fermented milk was higher when vegetal oils and LAB were used. This study demonstrates that LAB can be used as potential starter or adjunct cultures in the production of CLA-enriched milk. μg/ml in presence of sunflower oil (200 and 400 μg/ml, respectively), and 59 and 101 μg/ml when soy oil was added at the same concentrations. Both LAB strains showed a similar CLA production level in presence of hydrolyzed sunflower or soy oils, and a lower LA conversion rate than that previously observed in MRS or LAPTg broth. This fact could be due to the high protein concentration of milk which could neutralize the toxic effect of free fatty acids on bacteria metabolism. However, CLA concentration in fermented milk was higher when vegetal oils and LAB were used. This study demonstrates that LAB can be used as potential starter or adjunct cultures in the production of CLA-enriched milk. when soy oil was added at the same concentrations. Both LAB strains showed a similar CLA production level in presence of hydrolyzed sunflower or soy oils, and a lower LA conversion rate than that previously observed in MRS or LAPTg broth. This fact could be due to the high protein concentration of milk which could neutralize the toxic effect of free fatty acids on bacteria metabolism. However, CLA concentration in fermented milk was higher when vegetal oils and LAB were used. This study demonstrates that LAB can be used as potential starter or adjunct cultures in the production of CLA-enriched milk.μg/ml. Results showed that growth rate and pH values were not affected during the milk fermentation, with or without vegetal oil addition. After 24 h of incubation (37ºC) CLA production in L. paracasei CRL 575 culture was 58 and 65 μg/ml, when sunflower oil was added as substrate (200 and 400 μg/ml, respectively). Higher levels of CLA (69 and 74 μg/ml) were determined in skim milk supplemented with soy oil at the same concentrations. Lact. lactis CRL 1434 showed a similar behaviour in milk enriched with soy or sunflower oils. CLA production was 65 and 87 μg/ml in presence of sunflower oil (200 and 400 μg/ml, respectively), and 59 and 101 μg/ml when soy oil was added at the same concentrations. Both LAB strains showed a similar CLA production level in presence of hydrolyzed sunflower or soy oils, and a lower LA conversion rate than that previously observed in MRS or LAPTg broth. This fact could be due to the high protein concentration of milk which could neutralize the toxic effect of free fatty acids on bacteria metabolism. However, CLA concentration in fermented milk was higher when vegetal oils and LAB were used. This study demonstrates that LAB can be used as potential starter or adjunct cultures in the production of CLA-enriched milk. μg/ml in presence of sunflower oil (200 and 400 μg/ml, respectively), and 59 and 101 μg/ml when soy oil was added at the same concentrations. Both LAB strains showed a similar CLA production level in presence of hydrolyzed sunflower or soy oils, and a lower LA conversion rate than that previously observed in MRS or LAPTg broth. This fact could be due to the high protein concentration of milk which could neutralize the toxic effect of free fatty acids on bacteria metabolism. However, CLA concentration in fermented milk was higher when vegetal oils and LAB were used. This study demonstrates that LAB can be used as potential starter or adjunct cultures in the production of CLA-enriched milk. when soy oil was added at the same concentrations. Both LAB strains showed a similar CLA production level in presence of hydrolyzed sunflower or soy oils, and a lower LA conversion rate than that previously observed in MRS or LAPTg broth. This fact could be due to the high protein concentration of milk which could neutralize the toxic effect of free fatty acids on bacteria metabolism. However, CLA concentration in fermented milk was higher when vegetal oils and LAB were used. This study demonstrates that LAB can be used as potential starter or adjunct cultures in the production of CLA-enriched milk.L. paracasei CRL 575 culture was 58 and 65 μg/ml, when sunflower oil was added as substrate (200 and 400 μg/ml, respectively). Higher levels of CLA (69 and 74 μg/ml) were determined in skim milk supplemented with soy oil at the same concentrations. Lact. lactis CRL 1434 showed a similar behaviour in milk enriched with soy or sunflower oils. CLA production was 65 and 87 μg/ml in presence of sunflower oil (200 and 400 μg/ml, respectively), and 59 and 101 μg/ml when soy oil was added at the same concentrations. Both LAB strains showed a similar CLA production level in presence of hydrolyzed sunflower or soy oils, and a lower LA conversion rate than that previously observed in MRS or LAPTg broth. This fact could be due to the high protein concentration of milk which could neutralize the toxic effect of free fatty acids on bacteria metabolism. However, CLA concentration in fermented milk was higher when vegetal oils and LAB were used. This study demonstrates that LAB can be used as potential starter or adjunct cultures in the production of CLA-enriched milk. μg/ml in presence of sunflower oil (200 and 400 μg/ml, respectively), and 59 and 101 μg/ml when soy oil was added at the same concentrations. Both LAB strains showed a similar CLA production level in presence of hydrolyzed sunflower or soy oils, and a lower LA conversion rate than that previously observed in MRS or LAPTg broth. This fact could be due to the high protein concentration of milk which could neutralize the toxic effect of free fatty acids on bacteria metabolism. However, CLA concentration in fermented milk was higher when vegetal oils and LAB were used. This study demonstrates that LAB can be used as potential starter or adjunct cultures in the production of CLA-enriched milk. when soy oil was added at the same concentrations. Both LAB strains showed a similar CLA production level in presence of hydrolyzed sunflower or soy oils, and a lower LA conversion rate than that previously observed in MRS or LAPTg broth. This fact could be due to the high protein concentration of milk which could neutralize the toxic effect of free fatty acids on bacteria metabolism. However, CLA concentration in fermented milk was higher when vegetal oils and LAB were used. This study demonstrates that LAB can be used as potential starter or adjunct cultures in the production of CLA-enriched milk.CRL 575 culture was 58 and 65 μg/ml, when sunflower oil was added as substrate (200 and 400 μg/ml, respectively). Higher levels of CLA (69 and 74 μg/ml) were determined in skim milk supplemented with soy oil at the same concentrations. Lact. lactis CRL 1434 showed a similar behaviour in milk enriched with soy or sunflower oils. CLA production was 65 and 87 μg/ml in presence of sunflower oil (200 and 400 μg/ml, respectively), and 59 and 101 μg/ml when soy oil was added at the same concentrations. Both LAB strains showed a similar CLA production level in presence of hydrolyzed sunflower or soy oils, and a lower LA conversion rate than that previously observed in MRS or LAPTg broth. This fact could be due to the high protein concentration of milk which could neutralize the toxic effect of free fatty acids on bacteria metabolism. However, CLA concentration in fermented milk was higher when vegetal oils and LAB were used. This study demonstrates that LAB can be used as potential starter or adjunct cultures in the production of CLA-enriched milk. μg/ml in presence of sunflower oil (200 and 400 μg/ml, respectively), and 59 and 101 μg/ml when soy oil was added at the same concentrations. Both LAB strains showed a similar CLA production level in presence of hydrolyzed sunflower or soy oils, and a lower LA conversion rate than that previously observed in MRS or LAPTg broth. This fact could be due to the high protein concentration of milk which could neutralize the toxic effect of free fatty acids on bacteria metabolism. However, CLA concentration in fermented milk was higher when vegetal oils and LAB were used. This study demonstrates that LAB can be used as potential starter or adjunct cultures in the production of CLA-enriched milk. when soy oil was added at the same concentrations. Both LAB strains showed a similar CLA production level in presence of hydrolyzed sunflower or soy oils, and a lower LA conversion rate than that previously observed in MRS or LAPTg broth. This fact could be due to the high protein concentration of milk which could neutralize the toxic effect of free fatty acids on bacteria metabolism. However, CLA concentration in fermented milk was higher when vegetal oils and LAB were used. This study demonstrates that LAB can be used as potential starter or adjunct cultures in the production of CLA-enriched milk.μg/ml, respectively). Higher levels of CLA (69 and 74 μg/ml) were determined in skim milk supplemented with soy oil at the same concentrations. Lact. lactis CRL 1434 showed a similar behaviour in milk enriched with soy or sunflower oils. CLA production was 65 and 87 μg/ml in presence of sunflower oil (200 and 400 μg/ml, respectively), and 59 and 101 μg/ml when soy oil was added at the same concentrations. Both LAB strains showed a similar CLA production level in presence of hydrolyzed sunflower or soy oils, and a lower LA conversion rate than that previously observed in MRS or LAPTg broth. This fact could be due to the high protein concentration of milk which could neutralize the toxic effect of free fatty acids on bacteria metabolism. However, CLA concentration in fermented milk was higher when vegetal oils and LAB were used. This study demonstrates that LAB can be used as potential starter or adjunct cultures in the production of CLA-enriched milk. μg/ml in presence of sunflower oil (200 and 400 μg/ml, respectively), and 59 and 101 μg/ml when soy oil was added at the same concentrations. Both LAB strains showed a similar CLA production level in presence of hydrolyzed sunflower or soy oils, and a lower LA conversion rate than that previously observed in MRS or LAPTg broth. This fact could be due to the high protein concentration of milk which could neutralize the toxic effect of free fatty acids on bacteria metabolism. However, CLA concentration in fermented milk was higher when vegetal oils and LAB were used. This study demonstrates that LAB can be used as potential starter or adjunct cultures in the production of CLA-enriched milk. when soy oil was added at the same concentrations. Both LAB strains showed a similar CLA production level in presence of hydrolyzed sunflower or soy oils, and a lower LA conversion rate than that previously observed in MRS or LAPTg broth. This fact could be due to the high protein concentration of milk which could neutralize the toxic effect of free fatty acids on bacteria metabolism. However, CLA concentration in fermented milk was higher when vegetal oils and LAB were used. This study demonstrates that LAB can be used as potential starter or adjunct cultures in the production of CLA-enriched milk.Lact. lactis CRL 1434 showed a similar behaviour in milk enriched with soy or sunflower oils. CLA production was 65 and 87 μg/ml in presence of sunflower oil (200 and 400 μg/ml, respectively), and 59 and 101 μg/ml when soy oil was added at the same concentrations. Both LAB strains showed a similar CLA production level in presence of hydrolyzed sunflower or soy oils, and a lower LA conversion rate than that previously observed in MRS or LAPTg broth. This fact could be due to the high protein concentration of milk which could neutralize the toxic effect of free fatty acids on bacteria metabolism. However, CLA concentration in fermented milk was higher when vegetal oils and LAB were used. This study demonstrates that LAB can be used as potential starter or adjunct cultures in the production of CLA-enriched milk. μg/ml in presence of sunflower oil (200 and 400 μg/ml, respectively), and 59 and 101 μg/ml when soy oil was added at the same concentrations. Both LAB strains showed a similar CLA production level in presence of hydrolyzed sunflower or soy oils, and a lower LA conversion rate than that previously observed in MRS or LAPTg broth. This fact could be due to the high protein concentration of milk which could neutralize the toxic effect of free fatty acids on bacteria metabolism. However, CLA concentration in fermented milk was higher when vegetal oils and LAB were used. This study demonstrates that LAB can be used as potential starter or adjunct cultures in the production of CLA-enriched milk. when soy oil was added at the same concentrations. Both LAB strains showed a similar CLA production level in presence of hydrolyzed sunflower or soy oils, and a lower LA conversion rate than that previously observed in MRS or LAPTg broth. This fact could be due to the high protein concentration of milk which could neutralize the toxic effect of free fatty acids on bacteria metabolism. However, CLA concentration in fermented milk was higher when vegetal oils and LAB were used. This study demonstrates that LAB can be used as potential starter or adjunct cultures in the production of CLA-enriched milk.