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

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

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

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

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

Dairy Streptococcus thermophilus improves cell viability of Lactobacillus brevis NPS-QW-145 and its γaminobutyric acid biosynthesis ability in milk

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Genomic insights into high exopolysaccharideproducing dairy starter bacterium Streptococcus thermophilus ASCC 1275

Conference Theme: Linking animal science and animal agriculture: Meeting the global demands of 2050Graduate Student Competition: ADSA Dairy Foods OralStreptococcus thermophilus ASCC 1275 (ST 1275) is a typical dairy starter bacterium and produces the highest known amount (1,000 mg/L) of exopolysaccharide (EPS) in milk within this species. This organism produces both capsular and ropy EPS and possesses textural modifying properties for yogurt and cheese. In this study, de novo shotgun paired-end pyrosequencing was applied to complete the whole genome of ST 1275. The genome size of ST 1275, a plasmid-free bacterium, was 1.85 Mbp with an average GC content of 39.1%. A novel eps gene cluster for EPS assembly containing two-pair genes of epsC- epsD for determining the chain length of EPS was found in ST 1275 genome, which confirms that ST 1275 produces two types of EPSs as found in our previous studies. Compared with other sequenced S. thermophilus strains, ST 1275 possessed the lowest numbers of 5 rRNA operons and 55 tRNAs suggesting that this organism may have a more effective protein synthesis machinery. The highest number of four separate CRISPR (clustered regularly interspaced short palindromic repeats)-Cas (CRISPR-associated) loci was found in ST 1275 genome indicating that this organism may have a better adaptive immunity against various bacteriophage infections. Further analysis including carbohydrate utilization, effective proteolytic system, sophisticated stress response systems and defense systems in ST 1275 was performed to provide genomic insights into its adaptation to milk and as a cell factory for EPS production during milk fermentation. The elucidation of ST 1275 genome makes this organism as a model dairy starter bacterium for the research of high EPS yield and capsular/ropy EPS producer from the species of S. thermophilus.published_or_final_versio

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

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Architecture for public safety network using D2D communication

Device to Device (D2D) communication has been proposed as an underlay to Long-Term evolution (LTE) network as a means of harvesting the proximity, reuse and hop gains. However, D2D communication can also serve as a technology for providing public safety and disaster relief services. In this article, the basic concepts of D2D communications are first introduced and then existing fundamental works on disaster communication are discussed. We focus on the performance of the network architecture by utilizing the relay assisted transmission which can effectively enhance the capacity and power saving of the network. We also propose the distance based strategy to reduce the computational complexity and power transmission. Finally, simulation results are provided to verify the proposed architecture

Common distribution of gad operon in Lactobacillus brevis and its GadA contributes to efficient GABA synthesis toward cytosolic near-neutral pH

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Effect of Nanosilica on the Sulfate Attack Resistivity of Cement Mortar

The effect of nanosilica on the sulfate attack resistivity of cement mortar was investigated through study on the mechanical property evolution and the length change of the cement mortar under 5 wt.% sodium sulfate for 6 months. Meanwhile, the effects were compared with those of fly ash-replacement mortar. Results showed that by taking the advantages of nanosilica and fly ash in improving the property of cement mortar at early and later ages, the sulfate attack resistance of cement mortar can be enhanced in mechanical property increase and expansion reduction. Further, it implies that a combination of both pozzolans could enhance the sulfate attack resistivity of cement-based materials