Lactobacillus growth and membrane composition in the presence of linoleic or conjugated linoleic acid

Tween 80™-induced changes in fatty acid profile of selected mesophilic lactobacilli

Fatty acid profiles are crucial for the functionality and viability of lactobacilli used in food applications. Tween 80™, a common culture media additive, is known to influence bacterial growth and composition. This study investigated how Tween 80™ supplementation impacts the fatty acid profiles of six mesophilic lactobacilli strains (Lacticaseibacillus spp., Limosilactobacillus spp., Lactiplantibacillus plantarum). Analysis of eleven strains revealed 29 distinct fatty acids. Tween 80™ supplementation significantly altered their fatty acid composition. Notably, there was a shift towards saturated fatty acids and changes within the unsaturated fatty acid profile. While some unsaturated fatty acids decreased, there was a concurrent rise in cyclic derivatives like lactobacillic acid (derived from vaccenic acid) and dihydrosterculic acid (derived from oleic acid). This suggests that despite the presence of Tween 80™ as an oleic acid source, lactobacilli prioritize the synthesis of these cyclic derivatives from precursor unsaturated fatty acids. Myristic acid and dihydrosterculic acid levels varied across strains. Interestingly, palmitic acid content increased, potentially reflecting enhanced incorporation of oleic acid from Tween 80™ into membranes. Conversely, cis-vaccenic acid levels consistently decreased across all strains. The observed fatty acid profiles differed from previous studies, likely due to a combination of factors including strain-specific variations and growth condition differences (media type, temperature, harvesting point). However, this study highlights the consistent impact of Tween 80™ on the fatty acid composition of lactobacilli, regardless of these variations. In conclusion, Tween 80™ significantly alters fatty acid profiles, influencing saturation levels and specific fatty acid proportions. This work reveals key factors, including stimulated synthesis of lactobacillic acid, competition for oleic acid incorporation, and strain-specific responses to myristic and dihydrosterculic acids. The consistent reduction in cis-vaccenic acid and the presence of cyclic derivatives warrant further investigation to elucidate their roles in response to Tween 80™ supplementation.

Alterations of the vaginal microbiome in healthy pregnant women positive for group B Streptococcus colonization during the third trimester

BACKGROUND

Streptococcus agalactiae or group B Streptococcus (GBS) asymptomatically colonizes the genitourinary tracts of up to 30% of pregnant women. Globally, GBS is an important cause of neonatal morbidity and mortality. GBS has recently been linked to adverse pregnancy outcomes. The potential interactions between GBS and the vaginal microbiome composition remain poorly understood. In addition, little is known about the vaginal microbiota of pregnant Egyptian women.

RESULTS

Using V3-V4 16S rRNA next-generation sequencing, we examined the vaginal microbiome in GBS culture-positive pregnant women (22) and GBS culture-negative pregnant women (22) during the third trimester in Ismailia, Egypt. According to the alpha-diversity indices, the vaginal microbiome of pregnant GBS culture-positive women was significantly more diverse and less homogenous. The composition of the vaginal microbiome differed significantly based on beta-diversity between GBS culture-positive and culture-negative women. The phylum Firmicutes and the family Lactobacillaceae were significantly more abundant in GBS-negative colonizers. In contrast, the phyla Actinobacteria, Tenericutes, and Proteobacteria and the families Bifidobacteriaceae, Mycoplasmataceae, Streptococcaceae, Corynebacteriaceae, Staphylococcaceae, and Peptostreptococcaceae were significantly more abundant in GBS culture-positive colonizers. On the genus and species levels, Lactobacillus was the only genus detected with significantly higher relative abundance in GBS culture-negative status (88%), and L. iners was the significantly most abundant species. Conversely, GBS-positive carriers exhibited a significant decrease in Lactobacillus abundance (56%). In GBS-positive colonizers, the relative abundance of the genera Ureaplasma, Gardnerella, Streptococcus, Corynebacterium, Staphylococcus, and Peptostreptococcus and the species Peptostreptococcus anaerobius was significantly higher. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways related to the metabolism of cofactors and vitamins, phosphatidylinositol signaling system, peroxisome, host immune system pathways, and host endocrine system were exclusively enriched among GBS culture-positive microbial communities. However, lipid metabolism KEGG pathways, nucleotide metabolism, xenobiotics biodegradation and metabolism, genetic information processing pathways associated with translation, replication, and repair, and human diseases (Staphylococcus aureus infection) were exclusively enriched in GBS culture-negative communities.

CONCLUSIONS

Understanding how perturbations of the vaginal microbiome contribute to pregnancy complications may result in the development of alternative, targeted prevention strategies to prevent maternal GBS colonization. We hypothesized associations between inferred microbial function and GBS status that would need to be confirmed in larger cohorts.

Probiotic Properties of Lactic Acid Bacteria with High Conjugated Linoleic Acid Converting Activity Isolated from Jeot-Gal, High-Salt Fermented Seafood

Conjugated linoleic acid (CLA) isomers are potent health-promoting fatty acids. This study evaluated the probiotic properties of 10 strains of high CLA-producing lactic acid bacteria (LAB) isolated from Jeot-gal, a high-salt, fermented seafood. Two isolates, Lactiplantibacillus plantarum JBCC105683 and Lactiplantibacillus pentosus JBCC105676, produced the largest amounts of CLA (748.8 and 726.9 μg/mL, respectively). Five isolates, L. plantarum JBCC105675, L. pentosus JBCC105676, L. pentosus JBCC105674, L. plantarum JBCC105683, and Lactiplantibacillus paraplantarum JBCC105655 synthesized more cis-9, trans-11-CLA than trans-10, cis-12-CLA (approximately 80:20 ratio). All the strains survived severe artificial acidic environments and showed antimicrobial activity and strong adhesion capability to Caco-2 cells as compared to the commercial strain Lactocaseibacillus rhamnosus GG. Among them, Pediococcus acidilactici JBCC105117, L. paraplantarum JBCC105655, and L. plantarum JBCC105683 strongly stimulated the immunological regulatory gene PMK-1 and the host defense antimicrobial peptide gene clec-60 in Caenorhabditis elegans. Moreover, three strains showed a significant induction of tumor necrosis factor-α, interleukin (IL)-1β, IL-6, IL-12, and IL-10 production in RAW 264.7 macrophages, indicating that they were promising candidates for probiotics with high CLA-converting activity. Our results indicate that the newly isolated CLA-producing LAB might be useful as a functional probiotic with beneficial health effects that modulate the immune system.

A Villin-Driven Fxr Transgene Modulates Enterohepatic Bile Acid Homeostasis and Response to an n-6-Enriched High-Fat Diet

A diet high in n-6 polyunsaturated fatty acids (PUFAs) may contribute to inflammation and tissue damage associated with obesity and pathologies of the colon and liver. One contributing factor may be dysregulation by n-6 fatty acids of enterohepatic bile acid (BA) metabolism. The farnesoid X receptor (FXR) is a nuclear receptor that regulates BA homeostasis in the liver and intestine. This study aims to compare the effects on FXR regulation and BA metabolism of a palm oil-based diet providing 28% energy (28%E) from fat and low n-6 linoleic acid (LA, 2.5%E) (CNTL) with those of a soybean oil-based diet providing 50%E from fat and high (28%E) in LA (n-6HFD). Wild-type (WT) littermates and a transgenic mouse line overexpressing the Fxrα1 isoform under the control of the intestine-specific Villin promoter (Fxrα1^TG) were fed the CNTL or n-6HFD starting at weaning through 16 weeks of age. Compared to the CNTL diet, the n-6HFD supports higher weight gain in both WT and Fxrα^TG littermates; increases the expression of Fxrα1/2, and peroxisome proliferator-activated receptor-γ1 (Pparγ1) in the small intestine, Fxrα1/2 in the colon, and cytochrome P4507A1 (Cyp7a1) and small heterodimer protein (Shp) in the liver; and augments the levels of total BA in the liver, and primary chenodeoxycholic (CDCA), cholic (CA), and β-muricholic (βMCA) acid in the cecum. Intestinal overexpression of the Fxra1^TG augments expression of Shp and ileal bile acid-binding protein (Ibabp) in the small intestine and Ibabp in the proximal colon. Conversely, it antagonizes n-6HFD-dependent accumulation of intestinal and hepatic CDCA and CA; hepatic levels of Cyp7a1; and expression of Pparγ in the small intestine. We conclude that intestinal Fxrα1 overexpression represses hepatic de novo BA synthesis and protects against n-6HFD-induced accumulation of human-specific primary bile acids in the cecum.

Cultivation media for lactic acid bacteria used in dairy products

This review aims to familiarize the reader with research efforts on the cultivation media of lactic acid bacteria (LAB). We have also included a brief discussion on standard ingredients used in LAB media and chemically defined media as related to bacterial growth requirements. Recent research has focused on modifying standard media for the enumeration, differentiation, isolation, and identification of starter cultures and probiotics. Even though large numbers of these media have been developed to serve dairy microbial control, they have failed to provide consistent results. The research consequently points to the need to develop a reliable lactobacilli growth medium for the dairy industry.

Effect of Prebiotics-Enhanced Probiotics on the Growth of Streptococcus mutans

Streptococcus mutans predominantly creates an acidic environment in an oral cavity. This results in dental demineralization and carious lesions. The probiotics are beneficial microorganisms that modulate the bacterial balance in the digestive system. Prebiotics are defined as nondigestible oligosaccharides that are utilized for the selective stimulation of the beneficial microorganisms. The objective of this study was to evaluate the efficacy of the prebiotics, galactooligosaccharides (GOS) and fructooligosaccharides (FOS), for enhancing the probiotic Lactobacillus acidophilus ATCC 4356, for inhibiting Streptococcus mutans (A32-2) for the prevention of dental caries. The growth rate of the S. mutans significantly decreased when cocultured with L. acidophilus in the GOS-supplemented medium at 3%, 4%, and 5%. In the FOS-supplemented medium, the growth rate of S. mutans significantly decreased in all concentrations when cocultured with L. acidophilus. There was no significant difference in the growth rate of L. acidophilus in all concentrations of either GOS or FOS. It can be concluded that the growth rate of S. mutans was significantly retarded when cocultured with L. acidophilus and the proper concentration of prebiotics. These prebiotics have potential for a clinical application to activate the function of the naturally intraoral L. acidophilus to inhibit S. mutans.

Optimized medium via statistical approach enhanced threonine production by Pediococcus pentosaceus TL-3 isolated from Malaysian food

BACKGROUND

Threonine is an essential amino acid that is extensively used in livestock industry as feed supplement due to its pronounced effect in improving the growth performance of animals. Application of genetically engineered bacteria for amino acid production has its share of controversies after eosinophils myalgia syndrome outbreak in 1980s. This has urged for continuous search for a food grade producer as a safer alternative for industrial amino acid production. Lactic acid bacteria (LAB) appear as an exceptional candidate owing to their non-pathogenic nature and reputation of Generally Recognized as Safe (GRAS) status. Recently, we have identified a LAB, Pediococcus pentosaceus TL-3, isolated from Malaysian food as a potential threonine producer. Thus, the objective of this study was to enhance the threonine production by P. pentosaceus TL-3 via optimized medium developed by using Plackett-Burman design (PBD) and central composite design (CCD).

RESULTS

Molasses, meat extract, (NH4)2SO4, and MnSO4 were identified as the main medium components for threonine production by P. pentosaceus TL-3. The optimum concentration of molasses, meat extract, (NH4)2SO4 and MnSO4 were found to be 30.79 g/L, 25.30 g/L, 8.59 g/L, and 0.098 g/L respectively based on model obtained in CCD with a predicted net threonine production of 123.07 mg/L. The net threonine production by P. pentosaceus TL-3 in the optimized medium was enhanced approximately 2 folds compared to the control.

CONCLUSIONS

This study has revealed the potential of P. pentosaceus TL-3 as a safer alternative to produce threonine. Additionally, the current study has identified the key medium components affecting the production of threonine by P. pentosaceus TL-3, followed by optimization of their concentrations by means of statistical approach. The findings of this study could act as a guideline for the future exploration of amino acid production by LAB.

Resilience of small intestinal beneficial bacteria to the toxicity of soybean oil fatty acids

Over the past century, soybean oil (SBO) consumption in the United States increased dramatically. The main SBO fatty acid, linoleic acid (18:2), inhibits in vitro the growth of lactobacilli, beneficial members of the small intestinal microbiota. Human-associated lactobacilli have declined in prevalence in Western microbiomes, but how dietary changes may have impacted their ecology is unclear. Here, we compared the in vitro and in vivo effects of 18:2 on Lactobacillus reuteri and L. johnsonii. Directed evolution in vitro in both species led to strong 18:2 resistance with mutations in genes for lipid biosynthesis, acid stress, and the cell membrane or wall. Small-intestinal Lactobacillus populations in mice were unaffected by chronic and acute 18:2 exposure, yet harbored both 18:2- sensitive and resistant strains. This work shows that extant small intestinal lactobacilli are protected from toxic dietary components via the gut environment as well as their own capacity to evolve resistance.

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.

Fermentation factors influencing the production of bacteriocins by lactic acid bacteria: a review

Lactic acid bacteria (LAB) are the major interest in food industry primarily by virtue of their biopreservative properties.

Characterization of Linoleate 10-Hydratase of Lactobacillus plantarum and Novel Antifungal Metabolites

Lactobacilli convert linoleic acid to the antifungal compound 10-hydroxy-12-octadecenoic acid (10-HOE) by linoleate 10-hydratase (10-LAH). However, the effect of this conversion on cellular membrane physiology and properties of the cell surface have not been demonstrated. Moreover, Lactobacillus plantarum produces 13-hydroxy-9-octadecenoic acid (13-HOE) in addition to 10-HOE, but the antifungal activity of 13-HOE was unknown. Phylogenetic analyses conducted in this study did not differentiate between 10-LAH and linoleate 13-hydratase (13-LAH). Thus, linoleate hydratases (LAHs) must be characterized through their differences in their activities of linoleate conversion. Four genes encoding putative LAHs from lactobacilli were cloned, heterologous expressed, purified and identified as FAD-dependent 10-LAH. The unsaturated fatty acid substrates stimulated the growth of lactobacilli. We also investigated the role of 10-LAH in ethanol tolerance, membrane fluidity and hydrophobicity of cell surfaces in lactobacilli by disruption of lah. Compared with the L. plantarum lah deficient strain, 10-LAH in wild-type strain did not exert effect on cell survival and membrane fluidity under ethanol stress, but influenced the cell surface hydrophobicity. Moreover, deletion of 10-LAH in L. plantarum facilitated purification of 13-HOE and demonstration of its antifungal activity against Penicillium roqueforti and Aspergillus niger.

Bacterial production of conjugated linoleic and linolenic Acid in foods: a technological challenge

Conjugated linoleic acid (CLA) and conjugated linolenic acid (CLNA) isomers are present in foods derived from ruminants as a result of the respective linoleic acid (LA) and α-linolenic acid (LNA) metabolism by ruminal microorganisms and in animals' tissues. CLA and CLNA have isomer-specific, health-promoting properties, including anticarcinogenic, antiatherogenic, anti-inflammatory, and antidiabetic activity, as well as the ability to reduce body fat. Besides ruminal microorganisms, such as Butyrivibrio fibrisolvens, many food-grade bacteria, such as bifidobacteria, lactic acid bacteria (LAB), and propionibacteria, are able to convert LA and LNA to CLA and CLNA, respectively. Linoleate isomerase activity, responsible for this conversion, is strain-dependent and probably related to the ability of the producer strain to tolerate the toxic effects of LA and LNA. Since natural concentrations of CLA and CLNA in ruminal food products are relatively low to exert their health benefits, food-grade bacteria with linoleate isomerase activity could be used as starter or adjunct cultures to develop functional fermented dairy and meat products with increased levels of CLA and CLNA or included in fermented products as probiotic cultures. However, results obtained so far are below expectations due to technological bottlenecks. More research is needed to assess if bacterial production kinetics can be increased and can match food processing requirements.

Implications of modifying membrane fatty acid composition on membrane oxidation, integrity, and storage viability of freeze-dried probiotic, Lactobacillus acidophilus La-5

The aim of this study was to investigate the effect of altering the fatty acid profile of the lipid membrane on storage survival of freeze-dried probiotic, Lactobacillus acidophilus La-5, as well as study the membrane integrity and lipid oxidation. The fatty acid composition of the lipid membrane of L. acidophilus La-5 was significantly different upon growth in MRS (containing Tween 80, an oleic acid source), or in MRS with Tween 20 (containing C12:0 and C14:0), linoleic, or linolenic acid supplemented. Bacteria grown in MRS showed the highest storage survival rates. No indications of loss of membrane integrity could be found, and membrane integrity could therefore not be connected with loss of viability. Survival of bacteria grown with linoleic or linolenic acid was more negatively affected by the presence of oxygen, than bacteria grown in MRS or with Tween 20 supplemented. A small, but significant, loss of linolenic acid during storage could be identified, and an increase of volatile secondary oxidation products during storage was found for bacteria grown in MRS, or with linoleic, or linolenic acid supplemented, but not for bacteria grown with Tween 20. Overall, the results indicate that lipid oxidation and loss of membrane integrity are not the only or most important detrimental reactions which can occur during storage. By altering the fatty acid composition, it was also found that properties of oleic acid gave rise to more robust bacteria than more saturated or unsaturated fatty acids did.

Enrichment of conjugated linoleic acid (CLA) in hen eggs and broiler chickens meat by lactic acid bacteria

1. The aim of this work was to compare conjugated linoleic acid (CLA) concentrations in chickens supplemented with 4 American Tissue Culture Collection (ATCC) bacterial strains, Lactobacillus plantarum, Lactobacillus lactis, Lactobacillus casei and Lactobacillus fermentum, and 4 isolates of Lactobacillus reuteri from camel, cattle, sheep and goat rumen extracts. 2. Micro-organisms were grown anaerobically in MRS broth, and 10(6) CFU/ml of bacteria were administered orally to mixed-sex, 1-d-old broiler chickens weekly for 4 weeks and to 23-week-old layer hens weekly for 6 weeks. 3. The 4 strains were evaluated for their effects on synthesis of CLA in hen eggs and broiler meat cuts. 4. Administration of pure Lactobacillus and isolated L. reuteri strains from camel, cattle, goat and sheep led to significantly increased CLA concentrations of 0.2-1.2 mg/g of fat in eggs and 0.3-1.88 mg/g of fat in broiler chicken flesh homogenates of leg, thigh and breast. 5. These data demonstrate that lactic acid bacteria of animal origin (L. reuteri) significantly enhanced CLA synthesis in both eggs and broiler meat cuts.

A simulated mucus layer protects Lactobacillus reuteri from the inhibitory effects of linoleic acid

Lactobacillus reuteri is a commensal, beneficial gut microbe that colonises the intestinal mucus layer, where it makes close contact with the human host and may significantly affect human health. Here, we investigated the capacity of linoleic acid (LA), the most common polyunsaturated fatty acid (PUFA) in a Western-style diet, to affect L. reuteri ATCC PTA 6475 prevalence and survival in a simulated mucus layer. Short-term (1 h) survival and mucin-agar adhesion assays of a log-phase L. reuteri suspension in intestinal water demonstrated that the simulated mucus layer protected L. reuteri against the inhibitory effects of LA by lowering its contact with the bacterial cell membrane. The protective effect of the simulated mucus layer was further evaluated using a more complex and dynamic model of the colon microbiota (SHIME®), in which L. reuteri survival was monitored during 6 days of daily exposure to LA in the absence (L-SHIME) and presence (M-SHIME) of a simulated mucus layer. After 6 days, luminal L- and M-SHIME L. reuteri plate counts had decreased by 3.1±0.5 and 2.6±0.9 log cfu/ml, respectively. Upon supplementation of 1.0 g/l LA, the decline in the luminal L. reuteri population started earlier than was observed for the control. In contrast, mucin-agar levels of L. reuteri (in the M-SHIME) remained unaffected throughout the experiment even in the presence of high concentrations of LA. Overall, the results of this study indicate the importance of the mucus layer as a protective environment for beneficial gut microbes to escape from stress by high loads of the antimicrobial PUFA LA to the colon, i.e. due to a Western-style diet.

Sweet potatoes as a basic component in developing a medium for the cultivation of lactobacilli

A sweet potato medium (SPM) was formed with extract from baked sweet potatoes supplemented with 0, 4, or 8 g/L of each nitrogen source (beef extract, yeast extract, and proteose peptone #3) to form SPM1, SPM2, and SPM3 respectively. Lactobacilli MRS was used as control medium. Ten Lactobacillus strains containing an average of 2.34 ± 0.29 log CFU/mL were inoculated individually into batches of MRS, SPM1, SPM2, and SPM3. The growth patterns for the tested Lactobacillus strains growing in SPM2 and SPM3 were found to be similar to that in MRS. The average final population after 24 h of incubation in MRS, SPM2, and SPM3 reached 10.41 ± 0.35, 10.59 ± 0.27, and 10.72 ± 0.19 log CFU/mL respectively. SPM2 and SPM3 maintained higher pH values throughout the incubation period than MRS. These findings indicate that SPM2 can be a suitable medium for the growth of Lactobacillus and can provide an alternative at low-cost.

A rapid method of screening lactic acid bacterial strains for conjugated linoleic acid production

A more rapid and simpler method than those currently used was developed to screen conjugated linoleic acid (CLA)-producing bacteria isolated from cow milk. The screening of 500 strains was completed in 10 d and the screening efficiency was 10%. One strain resembling a Lactobacillus paracasei strain and two resembling L. helveticus strains converted free linoleic acid to total CLA ≥85%.

Use of statistical tools to evaluate the reductive dechlorination of high levels of TCE in microcosm studies

A large, multi-laboratory microcosm study was performed to select amendments for supporting reductive dechlorination of high levels of trichloroethylene (TCE) found at an industrial site in the United Kingdom (UK) containing dense non-aqueous phase liquid (DNAPL) TCE. The study was designed as a fractional factorial experiment involving 177 bottles distributed between four industrial laboratories and was used to assess the impact of six electron donors, bioaugmentation, addition of supplemental nutrients, and two TCE levels (0.57 and 1.90 mM or 75 and 250 mg/L in the aqueous phase) on TCE dechlorination. Performance was assessed based on the concentration changes of TCE and reductive dechlorination degradation products. The chemical data was evaluated using analysis of variance (ANOVA) and survival analysis techniques to determine both main effects and important interactions for all the experimental variables during the 203-day study. The statistically based design and analysis provided powerful tools that aided decision-making for field application of this technology. The analysis showed that emulsified vegetable oil (EVO), lactate, and methanol were the most effective electron donors, promoting rapid and complete dechlorination of TCE to ethene. Bioaugmentation and nutrient addition also had a statistically significant positive impact on TCE dechlorination. In addition, the microbial community was measured using phospholipid fatty acid analysis (PLFA) for quantification of total biomass and characterization of the community structure and quantitative polymerase chain reaction (qPCR) for enumeration of Dehalococcoides organisms (Dhc) and the vinyl chloride reductase (vcrA) gene. The highest increase in levels of total biomass and Dhc was observed in the EVO microcosms, which correlated well with the dechlorination results.

Modification of the technical properties of Lactobacillus johnsonii NCC 533 by supplementing the growth medium with unsaturated fatty acids

The aim of this study was to investigate the influence of supplementing growth medium with unsaturated fatty acids on the technical properties of the probiotic strain Lactobacillus johnsonii NCC 533, such as heat and acid tolerance, and inhibition of Salmonella enterica serovar Typhimurium infection. Our results showed that the membrane composition and morphology of L. johnsonii NCC 533 were significantly changed by supplementing a minimal Lactobacillus medium with oleic, linoleic, and linolenic acids. The ratio of saturated to unsaturated plus cyclic fatty acids in the bacterial membrane decreased by almost 2-fold when minimal medium was supplemented with unsaturated fatty acids (10 μg/ml). The subsequent acid and heat tolerance of L. johnsonii decreased by 6- and 20-fold when the strain was grown in the presence of linoleic and linolenic acids, respectively, compared with growth in oleic acid (all at 10 μg/ml). Following acid exposure, significantly higher (P < 0.05) oleic acid content was detected in the membrane when growth medium was supplemented with linoleic or linolenic acid, indicating that saturation of the membrane fatty acids occurred during acid stress. Cell integrity was determined in real time during stressed conditions using a fluorescent viability kit in combination with flow cytometric analysis. Following heat shock (at 62.5°C for 5 min), L. johnsonii was unable to form colonies; however, 60% of the bacteria showed no cell integrity loss, which could indicate that the elevated heat inactivated vital processes within the cell, rendering it incapable of replication. Furthermore, L. johnsonii grown in fatty acid-enriched minimal medium had different adhesion properties and caused a 2-fold decrease in S. enterica serovar Typhimurium UK1-lux invasion of HT-29 epithelial cells compared with bacteria grown in minimal medium alone. This could be related to changes in the hydrophobicity and fluidity of the membrane. Our study shows that technical properties underlying probiotic survivability can be affected by nutrient composition of the growth medium.

Functional and phenotypic characterization of a protein from Lactobacillus acidophilus involved in cell morphology, stress tolerance and adherence to intestinal cells

Structural components of the cell surface have an impact on some of the beneficial attributes of probiotic bacteria. In silico analysis of the L. acidophilus NCFM genome sequence revealed the presence of a putative cell surface protein that was predicted to be a myosin cross-reactive antigen (MCRA). As MCRAs are conserved among many probiotic bacteria, we used the upp-based counterselective gene replacement system, designed recently for use in L. acidophilus, to determine the functional role of this gene (LBA649) in L. acidophilus NCFM. Phenotypic assays were undertaken with the parent strain (NCK1909) and deletion mutant (NCK2015) to assign a function for this gene. The growth of NCK2015 (ΔLBA649) was reduced in the presence of lactate, acetate, porcine bile and salt. Adhesion of NCK2015 to Caco-2 cells was substantially reduced for both stationary-phase (∼45 % reduction) and exponential-phase cells (∼50 % reduction). Analysis of NCK2015 by scanning electron microscopy revealed a longer cell morphology after growth in MRS broth compared to NCK1909. These results indicate a role for LBA649 in stress tolerance, cell wall division and adherence to Caco-2 cells.

Growth inhibition of foodborne and pathogenic bacteria by conjugated linoleic acid

The influence of conjugated linoleic acid (CLA) on the growth of some foodborne and pathogenic bacteria was examined. A potassium salt of CLA (CLA-K) was tested against three Gram-positive strains ( Bacillus cereus , Staphylococcus aureus , and Streptococcus mutans ) and five Gram-negative strains ( Pseudomonas aeruginosa , Salmonella typhimurium , Vibrio parahemolyticus , Klebsiella pneumoniae , and Proteus mirabilis ). CLA-K-mediated growth inhibition was evident for all tested strains, particularly the Gram-positive strains. The IC(50) value of CLA-K was 0.3 mM for B. cereus, 1.2 mM for S. aureus, and 0.3 mM for S. mutans, whereas the value was 1.2 mM for K. pneumoniae, 1.2 mM for P. aeruginosa, 1.8 mM for S. typhimurium, 1.8 mM for V. parahemolyticus, and 2.4 mM for P. mirabilis. The CLA-K delayed the growth of all the tested strains at lower CLA-K concentrations, but completely inhibited the growth at higher concentrations. All cells grown in the medium containing CLA-K contained CLA in their membranes and exhibited irregular cell surface and cell disruption, which were greater in Gram-positive than Gram-negative strains. Higher lactic dehydrogenase activity (LDH), protein content, and malondialdehyde (MDA) content were evident in Gram-positive strains than in Gram-negative strains. These results suggest that the broad spectrum of growth inhibition by CLA mediated through the lipid peroxidation of CLA in the membranes and in the medium.

Probiotic modulation of symbiotic gut microbial-host metabolic interactions in a humanized microbiome mouse model

The transgenomic metabolic effects of exposure to either Lactobacillus paracasei or Lactobacillus rhamnosus probiotics have been measured and mapped in humanized extended genome mice (germ-free mice colonized with human baby flora). Statistical analysis of the compartmental fluctuations in diverse metabolic compartments, including biofluids, tissue and cecal short-chain fatty acids (SCFAs) in relation to microbial population modulation generated a novel top-down systems biology view of the host response to probiotic intervention. Probiotic exposure exerted microbiome modification and resulted in altered hepatic lipid metabolism coupled with lowered plasma lipoprotein levels and apparent stimulated glycolysis. Probiotic treatments also altered a diverse range of pathways outcomes, including amino-acid metabolism, methylamines and SCFAs. The novel application of hierarchical-principal component analysis allowed visualization of multicompartmental transgenomic metabolic interactions that could also be resolved at the compartment and pathway level. These integrated system investigations demonstrate the potential of metabolic profiling as a top-down systems biology driver for investigating the mechanistic basis of probiotic action and the therapeutic surveillance of the gut microbial activity related to dietary supplementation of probiotics.

Heterologous expression of linoleic acid isomerase from Propionibacterium acnes and anti-proliferative activity of recombinant trans-10, cis-12 conjugated linoleic acid

The linoleic acid isomerase enzyme from Propionibacterium acnes responsible for bioconversion of linoleic acid to trans-10, cis-12 conjugated linoleic acid (t10, c12 CLA) was cloned and overexpressed in Lactococcus lactis and Escherichia coli, resulting in between 30 and 50 % conversion rates of the substrate linoleic acid to t10, c12 CLA. The anti-proliferative activities of the fatty acids produced following isomerization of linoleic acid by L. lactis and E. coli were assessed using the human SW480 colon cancer cell line. Fatty acids generated from both L. lactis and E. coli contained a mixture of linoleic acid and t10, c12 CLA at a ratio of ∼1.35 : 1. Following 5 days of incubation of SW480 cells with 5–20 μg ml⁻¹ (17.8–71.3 μM) of the t10, c12 CLA, there was a significant (P<0.001) reduction in growth of the SW480 cancer cells compared with the linoleic acid control. Cell viability after treatment with the highest concentration (20 μg ml⁻¹) of the t10, c12 CLA was reduced to 7.9 % (L. lactis CLA) and 19.6 % (E. coli CLA), compared with 95.4 % (control linoleic acid) and 31.7 % (pure t10, c12 CLA). In conclusion, this is believed to represent the first report in which recombinant strains are capable of producing CLA with an anti-proliferative potential.

The effect of drinking milk containing conjugated linoleic acid on fecal microbiological profile, enzymatic activity, and fecal characteristics in humans

Background

The primary objective was to determine whether consumption of conjugated linoleic acids (CLAs) affected the fecal microbiota composition, fecal enzyme activity or fecal composition.

Methods

Human subjects consumed (1 L/day) cows' milk (4% fat) containing (5 mg/g fat) cis-9, trans-11 CLA (CONT), (32 mg/g fat) cis-9, trans-11 CLA (NAT) and (32 mg/g fat) trans-10, cis-12 CLA and cis-9, trans-11 CLA (SYN) for 8 weeks, in addition to their normal diet. Milk feeding periods were separated by 4 week washout periods. Fecal samples were obtained at the beginning (day 0) and the end (day 56) of each milk feeding period. Fecal samples were analysed for microbiological profile, enzyme activity, pH and short chain fatty acid content.

Results

Samples taken at day 0 and day 56 indicated that the numbers of lactobacilli and bifidobacteria significantly decreased after consumption of all experimental milks; total aerobes, total anaerobes, enterobacteria, and enterococci + streptococci did not change. At day 56, the activities of β-glucosidase, nitroreductase, and urease enzymes had decreased compared to samples taken on day 0 for all treatments. β-glucuronidase activity did not change. Fecal pH and ammonia content did not change.

Conclusion

It was concluded that observed changes could have been attributed to increased milk intake; no differences could be attributed to consumption of the different CLAs.

Trans fatty acids promote the growth of some Lactobacillus strains

Five Lactobacillus strains (2 L. gasseri, 2 L. plantarum and 1 L. reuteri) were cultured in modified MRS medium containing fatty acids (FAs) instead of Tween 80 for 24 h at 37 degrees C, to learn the effect of saturated and unsaturated FAs on the Lactobacillus growth. Free FAs included palmitic (16:0), palmitoleic (c9-16:1), stearic (18:0), oleic (c9-18:1), elaidic (t9-18:1), cis-vaccenic (c11-18:1), vaccenic (t11-18:1), linoleic (c9, c12-18:2), conjugated linoleic (c9, t11- and t10, c12-18:2), alpha-linolenic (c9, c12, c15-18:3), alpha-eleostearic (c9, t11, t13-18:3), eicosapentaenoic (20:5), and docosahexaenoic (22:6) acids. Among free FAs, oleic acid stimulated the growth of all Lactobacillus strains, whereas palmitoleic acid had almost no affect on the Lactobacillus growth. Saturated FAs such as stearic and palmitic acids inhibited or did not affect the Lactobacillus growth. Polyunsaturated FAs such as alpha-linolenic, eicosapentaenoic and docosahexaenoic acids strongly inhibited the Lactobacillus growth at 7.6 x 10(-4) m. Octadecenoic acids such as oleic, elaidic, cis-vaccenic and vaccenic acids remarkably promoted the growth of L. gasseri, regardless of the different double bond positions and configurations. When oleic or cis-vaccenic acid was incubated with L. gasseri, the FAs was transformed to cyclopropane FAs (methyleneoctadecanoic acids) after incorporation into the cells. On the other hand, trans FAs such as elaidic and vaccenic acids incorporated into the cells were not converted to another FAs. Conjugated linoleic and alpha-eleostearic acids having a trans double bond promoted the Lactobacillus growth. The growth of L. gasseri was also stimulated by trans-rich free FAs from hydrogenated canola and fish oils. These results showed that octadecenoic acid and trans FAs had strong promotion activities for the Lactobacillus growth due to their incorporation into membrane lipids.