Optimization of pH, time, temperature, variety and concentration of the added fatty acid and the initial count of added lactic acid Bacteria strains to improve microbial conjugated linoleic acid production in fermented ground beef.

The aim of the present study was to determine the optimum pH, time, temperature, variety and concentration of the added fatty acid and the initial count of added Lactobacillus plantarum AB20-961 and Lactobacillus plantarum DSM2601 for high conjugated linoleic acid (CLA) production in ground beef. The highest CLA production with using safflower fatty acids by L. plantarum AB20-961 and L. plantarum DSM2601 was 7.91 and 38.31 mg CLA/g fat, respectively (P < 0.05). Optimum conditions for both strains were 37 °C fermentation temperature, 5% added fatty acid in free form and 8 log CFU/g initial count. Additionally, the optimum pH and fermentation time were 7.94 pH and 78.78 h for L. plantarum AB20-961 and 7.68 and 72.57 h for L. plantarum DSM2601. The results indicated that both L. plantarum strains with optimum conditions determined in the present study may be applied in order to enrich CLA content in ground beef and satisfy consumer demands for the fermented meat products with functional components.

Utilization of optimized processing conditions for high yield synthesis of conjugated linoleic acid by L. plantarum AB20-961 and L. plantarum DSM2601 in semi-dry fermented sausage.

The aim of this study was to utilize optimized processing conditions to obtain the highest conjugated linoleic acid (CLA) contents in semi-dry fermented sausages produced with L. plantarum AB20-961 and L. plantarum DSM 2601. Optimized conditions were 5.7 meat pH, 5% hydrolyzed safflower oil addition, 108 CFU/g added starter culture, fermentation time of 73 h for L. plantarum DSM2601 and 79 h for L. plantarum AB20-961, 24 °C fermentation temperature, 65 °C internal cooking temperature and 90% relative humidity. Results indicated that CLA contents in sausages were increased 21% by L. plantarum AB20-961 and 121% by L. plantarum DSM2601 after fermentation compared to initial CLA level determined on manufacturing day (P < .05). After fermentation, an increased CLA content of sausages remained stable during heat processing and storage. Sausages incorporated with L. plantarum strains and hydrolyzed safflower oil had the highest TBARS and PUFA levels, and the lowest pH and moisture content (P < .05). Differences were not found in sensorial and other physicochemical properties among sausage treatment groups. This study demonstrated that high CLA content can be achieved in sausages by utilizing optimum processing conditions described above and starter cultures (L. plantarum AB20-961 and L. plantarum DSM2601) without any adverse effects on quality of the final product.

Genetic determinates for conjugated linolenic acid production in Lactobacillus plantarum ZS2058.

AIMS: To investigate the genetic determinates for conjugated linolenic acid (CLNA) production in Lactobacillus plantarum ZS2058, a high CLNA producer. METHODS AND RESULTS: After culturing with α-linolenic acid (ALA) in the medium, the fatty acid compositions of supernatant fluid and cell pellets were analysed via GC-MS. cis9,trans11,cis15-CLNA was identified to be the predominant isomer. And during CLNA production, 10-hydroxy-cis12-cis15-octadecenoic acid (10-HOEA) and 10-oxo-cis12-cis15-octadecenoic acid (10-OXOA) were accumulated. The E. coli recombinants harbouring genes encoding myosin-cross-reactive antigen (MCRA), short-chain dehydrogenase/oxidoreductase (DH) and acetoacetate decarboxylase (DC), respectively, were analysed for their roles in CLNA production. The results indicated that MCRA converted ALA to 10-HOEA, following converted to 10-OXOA by DH. While with the combination of three recombinants, ALA could be transformed into CLNA plus 10-HOEA and 10-OXOA. When the three genes were deleted, none of the L. plantarum ZS2058 knockout mutants could produce any CLNA, after complementation, and all the complementary mutants recovered the CLNA-production ability at similar levels as the wild strain. CONCLUSIONS: Lactobacillus plantarum ZS2058 produced CLNA from ALA with 10-HOEA and 10-OXOA as intermediates. The triple-component isomerase of MCRA, DH and DC was the unique genetic determinant for CLNA generation. SIGNIFICANCE AND IMPACT OF THE STUDY: The current results firstly provided conclusive evidence that the triple-component isomerase complex was shared by both CLA and CLNA production in lactobacilli.

Bacterial conjugated linoleic acid production and their applications.

Conjugated linoleic acid (CLA) has been shown to exert various potential physiological properties including anti-carcinogenic, anti-obesity, anti-cardiovascular and anti-diabetic activities, and consequently has been considered as a promising food supplement. Bacterial biosynthesis of CLA is an attractive approach for commercial production due to its high isomer-selectivity and convenient purification process. Many bacterial species have been reported to convert free linoleic acid (LA) to CLA, hitherto only the precise CLA-producing mechanisms in Propionibacterium acnes and Lactobacillus plantarum have been illustrated completely, prompting the development of recombinant technology used in CLA production. The purpose of the article is to review the bacterial CLA producers as well as the recent progress on describing the mechanism of microbial CLA-production. Furthermore, the advances and potential in the heterologous expression of CLA genetic determinants will be presented.

One-pot conjugated linoleic acid production from castor oil by Rhizopus oryzae lipase and resting cells of Lactobacillus plantarum.

Conjugated linoleic acid (CLA) has attracted as novel type of fatty acids having unusual health-promoting properties such as anticarcinogenic and antiobesitic effects. The present work employed castor oil as substrate for one-pot production of CLA using washed cells of Lactobacillus plantarum (L. plantarum) and lipases as catalysts. Among the screened lipases, the lipase Rhizopus oryzae (ROL) greatly assisted resting cells to produce CLA. Mass spectral analysis of the product showed that two major isomers of CLA were produced in the reaction mixture i.e. cis-9, trans-11 56.55% and trans-10, cis-12 43.45%. Optimum factors for CLA synthesis were found as substrate concentration (8 mg/mL), pH (6.5), washed cell concentration (12% w/v), and incubation time of 20 h. Hence, the combination of ROL with L. plantarum offers one pot production of CLA selectively using castor oil as a cost-effective substrate.

Strategies for Producing and Incorporating Conjugated Linoleic Acid-Rich Oils in Foods.

Conjugated linoleic acid (CLA) is in ruminant-derived foods and is known to combat obesity-related diseases. However, CLA levels in a healthy diet are too low to produce a clinical effect. Therefore, CLA has been produced by linoleic isomerization through fermentation and chemical catalysis. Many of these techniques are not practical for food production, but a recent development has enabled production of CLA-rich triglyceride vegetable oils from high linoleic acid oils by a minor modification of conventional food-oil processing techniques. These oils were used to produce common lipid-based food, such as margarine, shortenings, and salad dressings, whose quality was enhanced by the presence of CLA-rich oil and provided a significant CLA source. Meat and egg CLA content and subsequent food quality can also be increased by addition of dietary CLA. However, consumer awareness of CLA benefits needs to increase prior to commercial-scale production of CLA-rich oil.

A metabolic engineering strategy for producing conjugated linoleic acids using the oleaginous yeast Yarrowia lipolytica.

Conjugated linoleic acids (CLAs) have been found to have beneficial effects on human health when used as dietary supplements. However, their availability is limited because pure, chemistry-based production is expensive, and biology-based fermentation methods can only create small quantities. In an effort to enhance microbial production of CLAs, four genetically modified strains of the oleaginous yeast Yarrowia lipolytica were generated. These mutants presented various genetic modifications, including the elimination of ß-oxidation (pox1-6∆), the inability to store lipids as triglycerides (dga1∆ dga2∆ are1∆ lro1∆), and the overexpression of the Y. lipolytica ∆12-desaturase gene (YlFAD2) under the control of the constitutive pTEF promoter. All strains received two copies of the pTEF-oPAI or pPOX-oPAI expression cassettes; PAI encodes linoleic acid isomerase in Propionibacterium acnes. The strains were cultured in neosynthesis or bioconversion medium in flasks or a bioreactor. The strain combining the three modifications mentioned above showed the best results: when it was grown in neosynthesis medium in a flask, CLAs represented 6.5% of total fatty acids and in bioconversion medium in a bioreactor, and CLA content reached 302 mg/L. In a previous study, a CLA degradation rate of 117 mg/L/h was observed in bioconversion medium. Here, by eliminating ß-oxidation, we achieved a much lower rate of 1.8 mg/L/h.

Advances in research on cis-9, trans-11 conjugated linoleic acid: a major functional conjugated linoleic acid isomer.

Conjugated linoleic acid (CLA) consists of a group of positional and geometric conjugated isomers of linoleic acid. Since the identification of CLA as a factor that can inhibit mutagenesis and carcinogenesis, thousands of studies have been conducted in the last several decades. Among the many isomers discovered, cis-9, trans-11 CLA is the most intensively studied because of its multiple, isomer-specific effects in humans and animals. This paper provides an overview of the available data on cis-9, trans-11 CLA, including its isomer-specific effects, biosynthesis, in vivo/in vitro research models, quantification, and the factors influencing its content in ruminant products.

Probiotic administration modifies the milk fatty acid profile, intestinal morphology, and intestinal fatty acid profile of goats.

The effect of a mixture of potentially probiotic bacteria (MPPB; Lactobacillus reuteri DDL 19, Lactobacillus alimentarius DDL 48, Enterococcus faecium DDE 39, and Bifidobacterium bifidum strains) on the milk fatty acid (FA) profile, with emphasis on cis-9,trans-11 conjugated linoleic acid (CLA) in the middle stage of goat lactation, was determined. In addition, the effects of MPPB feeding on the FA profile in intestinal content and intestinal morphology in weaned goats were analyzed. The probiotic supplement was able to modify FA composition of milk and intestinal content. The unsaturated FA concentrations in milk (g of FA/L of milk) increased from 4.49 to 7.86 for oleic (18:1), from 0.70 to 1.39 for linoleic (18:2), from 0.063 to 0.187 for linolenic (18:3) acid, and from 0.093 to 0.232 for CLA. The atherogenicity index diminished 2-fold after MPPB ingestion. In the intestinal content of the weaned goats, no significant difference in saturated FA concentration compared with the control was observed. However, oleic acid, linolenic acid, CLA, and docosahexaenoic acid concentrations increased by 81, 23, 344, and 74%, respectively, after probiotic consumption. The ruminal production of CLA was increased by the MPPB. However, bacterial strains of MPPB were unable to produce CLA in culture media. By histological techniques, it was observed that the treated group had intestinally more conserved morphological structures than the control group. The results obtained in this study indicate that the MPPB administration in lactating and weaned goats allows for the production of milk with improved concentrations of beneficial compounds, and also produces a protective effect in the goat intestine. The results obtained in this study reinforce the strategy of probiotics application to enhance goat health with the production of milk with higher concentrations of polyunsaturated FA.

Appraisal of conjugated linoleic acid production by probiotic potential of Pediococcus spp. GS4.

Probiotics with ability to produce conjugated linoleic acid (CLA) is considered as an additive health benefit property for its known role in colon cancer mitigation. The conversion involves the biohydrogenation of the unsaturated fatty acid into conjugated form. Probiotic strain Pediococcus spp. GS4 was efficiently able to biohydrogenate linoleic acid (LA) into its conjugated form within 48 h of incubation. Quantum of CLA produced with a concentration of 121 µg/ml and sustained cell viability of 8.94 log cfu/ml maximally. Moreover, antibacterial effect of LA on the strain ability for biohydrogenation was examined at different concentrations and concluded to have a direct relationship between LA and amount of CLA produced. The efficiency of the strain for CLA production at different pH was also estimated and found maximum at pH 6.0 with 149 µg/ml while this ability was reduced at pH 9.0 to 63 µg/ml. Sesame oil, which is rich in the triacylglycerol form of LA, was also found to act as a substrate for CLA production by Pediococcus spp. GS4 with the aid of lipase-catalyzed triacylglycerol hydrolysis and amount of CLA produced was 31 µg/ml at 0.2 % while 150 µg/ml at 1.0 % of lipolysed oil in skim milk medium. Conjugated form was analyzed using UV scanning, RP-HPLC, and GC-MS. This study also focused on the alternative use of lipolysed sesame oil instead of costly LA for biohydrogenation and could be a potential source for the industrial production of CLA.

Short communication: in vivo deposition of [1-13C]vaccenic acid and the product of its Δ9-desaturation, [1-13C]rumenic acid, in the body tissues of lactating goats fed oils.

This study was conducted in lactating goats with the aim of measuring the deposition of trans-11 18:1 (vaccenic acid, VA) and the product of its Δ(9)-desaturation, cis-9, trans-11 18:2 (rumenic acid, RA), in the major tissues that are involved in lipid metabolism in the lactating ruminant (i.e., mammary secretory tissue, liver, and omental and perirenal adipose tissues) and examining its potential link with variations in the expression of genes encoding Δ(9)-desaturase [stearoyl-CoA desaturases 1 and 5 (SCD1 and SCD5)]. Eight lactating goats were fed a diet supplemented with sunflower oil (n=4) or sunflower oil plus fish oil and additional starch (n=4), based on the hypothesis that these dietary treatments could affect Δ(9)-desaturase gene expression in specific tissues. A chemical tracer, 1.5 g of [1-13C]VA as nonesterified fatty acid, was delivered by jugular injection. Goats were slaughtered 4 d later, and tissue samples were collected for the measurement of [13C]VA and [13C]RA enrichment and SCD1 and SCD5 expression. The addition of fish oil and additional starch to a diet containing sunflower oil was associated with several changes in [13C]VA and [13C]RA enrichment. These results support previous studies suggesting that mammary secretory tissue is the primary site of Δ(9)-desaturation in lactating goats. In adipose tissues, the [13C]VA + [13C]RA enrichment was consistent with a net uptake of circulating fatty acids to reconstitute body reserves at the end of the lactation cycle. The putative uptake of [13C]RA synthesized by other tissues precludes any conclusion from being drawn regarding potential Δ(9)-desaturation in the liver of goats, despite the detection of SCD1 and SCD5 mRNA in this tissue. Finally, no significant effect of dietary treatment was observed for SCD1 or SCD5 mRNA abundance in the mammary secretory tissue or other body tissues.

Lipids in the diet and the fatty acid profile in beef: a review and recent patents on the topic.

The objective of this review is to report how the use of lipid sources in diets for ruminants can affect the fatty acid profile of beef. In addition, recent patents that can be utilized to alter the fatty acid profile in the meat, or which concern the synthesis of conjugated fatty acids will be reviewed. The industrial production of conjugated linoleic acid (CLA) has already started and the commercial products present isomers cis-9, trans-11; trans-9, cis-11; and trans-10, cis-12. Patents on the biological synthesis of isomer C18:2 cis-9, trans-11 from the linoleic acid have also been published. However, the economic production of CLA in industrial scale is a difficult process. Most of the patents published for CLA production utilize bacteria of the genera Bifidobacterium sp. and Propionibacterium sp. Lipid supplementation, with the objective to improve the fatty acid profile of beef, can be done through the use of patented products, such as genetically modified oilseeds and calcium soaps of fatty acids.

Conjugated linoleic and linolenic acid production kinetics by bifidobacteria differ among strains.

There is great interest in conjugated linoleic acid (CLA) and conjugated linolenic acid (CLNA) isomers because of their supposed health-promoting properties. Therefore, the differences in production kinetics of CLA and CLNA isomers from linoleic acid (LA) and α-linolenic acid (α-LNA), respectively, by bifidobacteria were investigated. Laboratory fermentations, supplemented with LA or α-LNA in the fermentation medium, were performed with Bifidobacterium bifidum LMG 10645, Bifidobacterium breve LMG 11040, B. breve LMG 11084, B. breve LMG 11613, B. breve LMG 13194, and Bifidobacterium pseudolongum subsp. pseudolongum LMG 11595. Conversion of LA and α-LNA to CLA and CLNA isomers, respectively, started immediately upon addition of the substrate fatty acids. During the active growth phase, the c9, t11-CLA isomer and the putative c9, t11, c15-CLNA isomer were formed. Further fermentation resulted in a reduction in the concentration of c9, t11-CLA and c9, t11, c15-CLNA and the subsequent production of the t9, t11-CLA isomer and the putative t9, t11, c15-CLNA isomer, respectively. Modelling of the growth and metabolite data indicated differences in production kinetics among the strains. Some strains displayed a high specific conversion of LA and α-LNA despite poor growth, whereas other strains grew well but displayed lower conversion. Production of specific CLA and CLNA isomers by bifidobacteria holds potential for the production of functional foods and could contribute to their probiotic properties.

Conversion of t11t13 CLA into c9t11 CLA in Caco-2 cells and inhibition by sterculic oil.

BACKGROUND: Conjugated linoleic acids (CLA), and principally c9t11 CLA, are suspected to have numerous preventive properties regarding non-infectious pathologies such as inflammatory diseases, atherosclerosis and several types of cancer. C9t11 CLA is produced in the rumen during biohydrogenation of linoleic acid, but can also be synthesized in mammalian tissues from trans-vaccenic acid (C18:1 t11) through the action of delta-9 desaturase (D9D). For several years, it is also known that c9t11 CLA can be synthesized from conjugated linolenic acids (CLnA), i.e. c9t11c13 CLnA and c9t11t13 CLnA. This study aimed at investigating to which extent and by which route c9t11 CLA can be produced from another isomer of CLA, the t11t13 CLA that is structurally very similar to c9t11t13 CLnA, in Caco-2 cells. METHODOLOGY/PRINCIPAL FINDINGS: Caco-2 cells were incubated for 24 h with 20 µmol/l of t11t13 CLA in the absence or presence of sterculic oil used as an inhibitor of D9D. Caco-2 cells were able to convert t11t13 CLA into c9t11 CLA, and c9t11t13 CLnA was formed as an intermediate compound. In the presence of sterculic oil, the production of this intermediate was decreased by 46% and the formation of c9t11 CLA was decreased by 26%. No other metabolite was detected. CONCLUSIONS/SIGNIFICANCE: These results not only highlight the conversion of t11t13 CLA into c9t11 CLA but demonstrate also that this conversion involves first a desaturation step catalysed by D9D to produce c9t11t13 CLnA and then the action of another enzyme reducing the double bond on the Δ13 position.

Fibers from fruit by-products enhance probiotic viability and fatty acid profile and increase CLA content in yoghurts.

This study evaluated the effect of the supplementation of total dietary fiber from apple, banana or passion fruit processing by-products on the post-acidification, total titratable acidity, bacteria counts and fatty acid profiles in skim milk yoghurts co-fermented by four different probiotics strains: Lactobacillus acidophilus L10 and Bifidobacterium animalis subsp. lactis BL04, HN019 and B94. Apple and banana fibers increased the probiotic viability during shelf-life. All the fibers were able to increase the short chain and polyunsaturated fatty acid contents of yoghurts compared to their respective controls. A synergistic effect between the type of fiber and the probiotic strain on the conjugated linoleic acid content was observed, and the amount of α-linolenic acid was increased by banana fiber. The results of this study demonstrate, for the first time, that fruit fibers can improve the fatty acid profile of probiotic yoghurts and point out the suitability of using fibers from fruit processing the by-products to develop new high value-added fermented dairy products.

Catalytic production of conjugated fatty acids and oils.

The reactive double bonds in conjugated vegetable oils are of high interest in industry. Traditionally, conjugated vegetable oils are added to paints, varnishes, and inks to improve their drying properties, while recently there is an increased interest in their use in the production of bioplastics. Besides the industrial applications, also food manufactures are interested in conjugated vegetable oils due to their various positive health effects. While the isomer type is less important for their industrial purposes, the beneficial health effects are mainly associated with the c9,t11, t10,c12 and t9,t11 CLA isomers. The production of CLA-enriched oils as additives in functional foods thus requires a high CLA isomer selectivity. Currently, CLAs are produced by conjugation of oils high in linoleic acid, for example soybean and safflower oil, using homogeneous bases. Although high CLA productivities and very high isomer selectivities are obtained, this process faces many ecological drawbacks. Moreover, CLA-enriched oils can not be produced directly with the homogeneous bases. Literature reports describe many catalytic processes to conjugate linoleic acid, linoleic acid methyl ester, and vegetable oils rich in linoleic acid: biocatalysts, for example enzymes and cells; metal catalysts, for example homogeneous metal complexes and heterogeneous catalysts; and photocatalysts. This Review discusses state-of-the-art catalytic processes in comparison with some new catalytic production routes. For each category of catalytic process, the CLA productivities and the CLA isomer selectivity are compared. Heterogeneous catalysis seems the most attractive approach for CLA production due to its easy recovery process, provided that the competing hydrogenation reaction is limited and the CLA production rate competes with the current homogeneous base catalysis. The most important criteria to obtain high CLA productivity and isomer selectivity are (1) absence of a hydrogen donor, (2) absence of catalyst acidity, (3) high metal dispersion, and (4) highly accessible pore architecture.

Rumen microbial response in production of CLA and methane to safflower oil in association with fish oil or/and fumarate.

Supplementation effect of fish oil and/or fumarate on production of conjugated linoleic acid (CLA) and methane by rumen microbes was examined when incubated with safflower oil. One hundred and twenty milligrams of safflower oil (SO), safflower oil with 24 mg fish oil (SOFO), safflower oil with 24 mmol/L fumarate (SOFA), or safflower oil with 24 mg fish oil and 24 mmol/L fumarate (SOFOFA) were added to the 90 mL culture solution. The culture solution was also made without any supplements (control). The SOFA and SOFOFA increased pH and propionate (C3) compared to other treatments from 3 h incubation time. An accumulated amount of total methane (CH(4) ) for 12 h incubation was decreased by all the supplements compared to control. The concentrations of c9,t11CLA for all the incubation times were increased in the treatments of SOFO, SOFA and SOFOFA compared to SO. The highest concentration of c9,t11CLA was observed from SOFOFA among all the treatments at all incubation times. Overall data indicate that supplementation of combined fumarate and/or fish oil when incubated with safflower oil could depress CH(4) generation and increase production of C(3) and CLA under the condition of current in vitro study.

Effects of fish oil and starch added to a diet containing sunflower-seed oil on dairy goat performance, milk fatty acid composition and in vivo delta9-desaturation of [13C]vaccenic acid.

The potential benefits on human health have prompted an interest in developing nutritional strategies for specifically increasing rumenic acid (RA) in ruminant milk. The aims of the present study were to (i) compare two dietary treatments with lipid supplements on milk yield and composition, (ii) measure the in vivo delta9-desaturation of vaccenic acid (VA) to RA using 13C-labelled VA and (iii) determine the effect of the dietary treatments on this variable. Treatments were 90 g sunflower-seed oil (SO) per d or 60 g sunflower-seed oil and 30 g fish oil per d plus additional starch (SFO), in a grassland hay-based diet given to eight Alpine goats in a 2 x 2 cross-over design with 21 d experimental periods. Milk yield and composition were similar between treatments. Goats fed SFO had higher milk 6 : 0-16 : 0 concentration, lower milk sigmaC18 concentrations and showed no effect on milk VA and RA, compared with SO. At the end of the experiment, intravenous injection of 1.5 g [13C]VA followed by measurements of milk lipid 13C enrichment showed that in vivo 31.7 and 31.6 % of VA was delta9-desaturated into milk RA in the caprine with the SO and SFO treatments, respectively. The expression of genes encoding for delta9-desaturase (or stearoyl-CoA desaturase; SCD1, SCD5) in mammary tissues and four milk delta9-desaturation ratios were similar between treatments. In conclusion, the present study provides the first estimates of in vivo endogenous synthesis of RA (63-73 % of milk RA) from VA in goats, and shows no difference between the two lipid supplements compared.

Optimization of a reconstituted skim milk based medium for enhanced CLA production by bifidobacteria.

AIMS: To determine the effect of a range of supplements on the bioconversion of linoleic acid to conjugated linoleic acid (CLA) by Bifidobacterium breve NCIMB 702258 in reconstituted skim milk (RSM). RESULTS: Seven supplements (yeast extract, casein hydrolysate, tryptone, l-cysteine hydrochloride, sodium acetate, sodium butyrate and sodium propionate) were identified as increasing the bioconversion of linoleic acid to c9, t11 CLA. Using these supplements, the percentage bioconversion of linoleic acid (0.35 mg ml(-l)) to the c9, t11 CLA isomer was elevated from 15.5 +/- 1.1% in 20% RSM (w/v) to 48.1 +/- 2.2% in the supplemented RSM. Through additional supplementation of 20 mg m1(-1) inulin and optimization of inoculum and linoleic acid concentration, the percentage bioconversion to c9, t11 CLA was increased to 55.0 + 3.2%. CONCLUSIONS: Through supplementation, the concentration of CLA produced by bifidobacteria in RSM can be increased to levels comparable to those observed in the synthetic medium cys-MRS. SIGNIFICANCE AND IMPACT OF THE STUDY: The impact of 22 supplements on the production of the c9, t11 CLA isomer by the strain B. breve NCIMB 702258 in milk has been determined. The results provide an understanding of the factors, which influence CLA production by bifidobacteria in RSM.

Kinetics of microbial hydrogenation of free linoleic acid to conjugated linoleic acids.

AIMS: To investigate the ability of selected probiotic bacterial strains to produce conjugated linoleic acid (CLA) and also to estimate the biohydrogenation kinetics of Lactobacillus acidophilus on the production of CLA from free linoleic acid (LA). METHODS AND RESULTS: Six probiotic bacteria, Lact. paracasei, Lact. rhamnosus GG, Lact. acidophilus ADH, and Bifidobacterium longum B6, Lact. brevis, and Lact. casei, were used to examine their ability to convert LA to CLA. LA tolerance was evaluated by addition of different LA concentrations in MRS broth. Lact. acidophilus showed the major tolerant to LA and the greatest CLA-producing ability (36-48 microg ml(-1) of CLA). The rate-controlling steps were k(2) and k(1) for the addition of 1 and 3 mg ml(-1) of LA, respectively. The percentage of CLA conversion was higher in MRS broth supplemented with 1 mg ml(-1) (65%) than 3 mg ml(-1) (26%). CONCLUSION: The results provide useful information and new approach for understanding the biohydrogenation mechanisms of CLA production. SIGNIFICANCE AND IMPACT OF THE STUDY: This study would help elucidate the pathway from LA to stearic acid (SA), known as biohydrogenation. In addition, the use of selected probiotic bacteria might lead to a significant improvement in food safety.