50,636 research outputs found

    Probiotics and health benefits with reference to synthesis of γ-aminobutyric acid by selected probiotic bacteria

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    Conference Theme: Linking animal science and animal agriculture: Meeting the global demands of 2050Dairy Foods Symposium: Dairy Foods Consumption, Gut Microbiota, and Human HealthTraditionally, probiotics have been added to yogurt and other fermented foods for health benefits. Currently 56 species of Lactobacillus, including L. acidophilus and L. casei and 32 species of Bifidobacterium, exist. These probiotic cultures are able to restore the normal balance of microbial populations in the intestine and offer several therapeutic benefits. There has been an increasing demand for health-promoting food ingredients. Different milks fermented with bacteria, yeasts, molds or enzymes offer a broad range of possibilities to cover different health aspects with new bioactive components such as lactoferrin, micronutrients, CLA, sphingolipids and bioactive peptides or synthesize exo-polysaccharides. In particular, milk-proteins and associated bioactive peptides released during microbial or enzymatic fermentation of milk offer a broad spectrum of new functional properties including anti-hypertensive, anti-microbial, anti-oxidative, and immuno-modulatory properties. Gamma-aminobutyric acid (GABA), a non -protein amino acid, is mainly found in the brain and regulates vertebrate physiological and psychological behaviors such as anxiety and depression blood pressure and hormone secretion. The synthesis of GABA in the brain decreases with age, especially in elders. Hence, there has been increasing interest in use of probiotics for GABA production. In this study, several GABA-producing LAB isolates have been isolated from naturally fermented foods such as Korean kimchi. Previous screening methods are time-consuming and inefficient. In the present study, we have developed a novel screening and identification method for GABA-producing LAB from Korean kimchi. Acid treatment was applied to screening procedure to obtain acid-tolerant LAB isolates, and then a simple identification of GABA-producing LAB based on release of gas by these bacteria has been developed. The amount of GABA produced by LAB isolates at various monosodium glutamate (MSG) concentrations and incubation times in MRS medium was quantified by HPLC. Genetic identification of high GABA-producing LAB was performed by both 16S rRNA gene and glutamate decarboxylase gene. Nine potential GABA-producing LAB isolates were selected by observing gas release during fermentation. The conversion ability of MSG into GABA for all nine LAB isolates was 100% (supplementation level 10 g/L MSG, incubation time 24 h), over 80% (supplementation level 30 g/L MSG, incubation 48 h), over 60% (supplementation level 50 g/L MSG, incubation time 72 h) and over 50% (supplementation level 70 g/L MSG, incubation time 72 h). These nine LAB isolates were genetically identified as Lactobacillus brevis by 16S rRNA gene and confirmed by glutamate decarboxylase gene.published_or_final_versio

    The potential of species-specific tagatose-6-phosphate (T6P) pathway in Lactobacillus casei group for galactose reduction in fermented dairy foods

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    Residual lactose and galactose in fermented dairy foods leads to several industrial and health concerns. There is very little information pertaining to manufacture of fermented dairy foods that are low in lactose and galactose. In the present study, comparative genomic survey demonstrated the constant presence of chromosome-encoded tagatose-6-phosphate (T6P) pathway in Lactobacillus casei group. Lactose/galactose utilization tests and β-galactosidase assay suggest that PTSGal system, PTSLac system and T6P pathway are major contributors for lactose/galactose catabolism in this group of organisms. In addition, it was found than lactose catabolism by Lb. casei group accumulated very limited galactose in the MRS-lactose medium and in reconstituted skim milk, whereas Streptococcus thermophilus and Lb. delbrueckii subsp. bulgaricus (Lb. bulgaricus) strains secreted high amount of galactose extracellularly. Moreover, co-culturing Lb. casei group with Str. thermophilus showed significant reduction in galactose content, while co-culturing Lb. casei group with Lb. bulgaricus showed significant reduction in lactose content but significant increase in galactose content in milk. Overall, the present study highlighted the potential of Lb. casei group for reducing galactose accumulation in fermented milks due to its species-specific T6P pathway.preprin

    High γ-aminobutyric acid production from lactic acid bacteria: emphasis on Lactobacillus brevis as a functional dairy starter

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    γ-Aminobutyric acid (GABA) and GABA-rich foods have shown anti-hypertensive and anti-depressant activities as the major functions in humans and animals. Hence, high GABA-producing lactic acid bacteria (LAB) could be used as functional starters for manufacturing novel fermented dairy foods. Glutamic acid decarboxylases (GADs) from LAB are highly conserved at the species level based on the phylogenetic tree of GADs from LAB. Moreover, two functionally distinct GADs and one intact gad operon were observed in all the completely sequenced Lactobacillus brevis strains suggesting its common capability to synthesize GABA. Difficulties and strategies for the manufacture of GABA-rich fermented dairy foods have been discussed and proposed, respectively. In addition, a genetic survey on the sequenced LAB strains demonstrated the absence of cell envelope proteinases in the majority of LAB including Lb. brevis, which diminishes their cell viabilities in milk environments due to their non-proteolytic nature. Thus, several strategies have been proposed to overcome the non-proteolytic nature of Lb. brevis in order to produce GABA-rich dairy foods.postprin

    Genomic insights into high exopolysaccharide-producing dairy starter bacterium Streptococcus thermophilus ASCC 1275

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    Poster presentationStreptococcus thermophilus is an essential dairy starter for the manufacture of yogurt and cheese. Whole-genome sequencing of this organism is expected to provide insights into the genetic basis of metabolic pathways for biotechnological and probiotic applications. Streptococcus thermophilus ASCC 1275, a high EPS-producing dairy starter, has shown texture-enhancing properties for yogurt and cheese. After genomic DNA extraction using CTAB/NaCl method, whole genome sequencing including one shot-gun sequencing, two extra paired-end sequencing and Sanger sequencing was performed for strain …postprin

    Radiation of the Inner Horizon of the Reissner-Nordstr\"om Black Hole

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    Despite of over thirty years of research of the black hole thermodynamics our understanding of the possible role played by the inner horizons of Reissner-Nordstr\"om and Kerr-Newman black holes in black hole thermodynamics is still somewhat incomplete: There are derivations which imply that the temperature of the inner horizon is negative and it is not quite clear what this means. Motivated by this problem we perform a detailed analysis of the radiation emitted by the inner horizon of the Reissner-Nordstr\"om black hole. As a result we find that in a maximally extended Reissner-Nordstr\"om spacetime virtual particle-antiparticle pairs are created at the inner horizon of the Reissner-Nordstr\"om black hole such that real particles with positive energy and temperature are emitted towards the singularity from the inner horizon and, as a consequence, antiparticles with negative energy are radiated away from the singularity through the inner horizon. We show that these antiparticles will come out from the white hole horizon in the maximally extended Reissner-Nordstr\"om spacetime, at least when the hole is near extremality. The energy spectrum of the antiparticles leads to a positive temperature for the white hole horizon. In other words, our analysis predicts that in addition to the radiation effects of black hole horizons, also the white hole horizon radiates. The black hole radiation is caused by the quantum effects at the outer horizon, whereas the white hole radiation is caused by the quantum effects at the inner horizon of the Reissner-Nordstr\"om black hole.Comment: 22 pages, 6 figures. References added, discussion slightly expanded in Secs. I and V. To appear in IJMP
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