Role of Probiotics, Prebiotics, and Synbiotics in the Elderly: Insights Into Their Applications.

Elderly people are an important part of the global population who suffer from the natural processes of senescence, which lead to changes in the gut microbiota composition. These modifications have a great impact on their quality of life, bringing a general putrefactive and inflammatory status as a consequence. Some of the most frequent conditions related to this status are constipation, undernutrition, neurodegenerative diseases, susceptibility to opportunistic pathogens, and metabolic disbalance, among others. For these reasons, there is an increasing interest in improving their quality of life by non-invasive treatments such as the consumption of probiotics, prebiotics, and synbiotics. The aim of the present mini-review is to describe the benefits of these functional supplements/food according to the most recent clinical and pre-clinical studies published during the last decade. In addition, insights into several aspects we consider relevant to improve the quality of future studies are provided.

Lactobacillus fermentum: Could EPS production ability be responsible for functional properties?

Exopolysaccharides (EPS) production is a characteristic that has been widely described for many lactic acid bacteria (LAB) of different genera and species, but little is known about the relationship between the functional properties of the producing bacteria and EPS synthesis. Although many studies were addressed towards the application of EPS-producing LAB in the manufacture of several dairy products (fermented milk, cheese) due to their interesting technological properties (increased hardness, water holding capacity, viscosity, etc.), there are not many reports about the functional properties of the EPS extract itself, especially for the genus Lactobacillus. The aim of the present revision is to focus on the species Lactobacillus fermentum with reported functional properties, with particular emphasis on those strains capable of producing EPS, and try to establish if there is any linkage between this property and their functional/probiotic roles, considering the most recent bibliography.

Structural characterisation of two medium molecular mass exopolysaccharides produced by the bacterium Lactobacillus fermentum Lf2.

Under optimized conditions, the lactic acid bacterium Lactobacillus fermentum Lf2 secretes up to 2 gL-1 of a mixture of polysaccharides into the fermentation medium when grown on sucrose. Earlier studies had shown that the mixture is biologically active and work was undertaken to characterise the polysaccharides. Preparative size exclusion chromatography was used to separate a high molecular mass ß-glucan (weight average mass of 1.23 × 106 gmol-1) from two medium molecular mass polysaccharides (weight average mass of 8.8 × 104 gmol-1). Under optimized growth conditions, the medium molecular mass polysaccharides accounted for more than 75% of the mixture by weight. Monomer, linkage analysis and NMR spectroscopy of the medium molecular mass polysaccharides, and material isolated after their Smith degradation, was used to identify the structure of the component polysaccharides. The mixture contains two novel polysaccharides. The first has a main chain of ß-1,6-linked galactofuranoses which is non-stoichiometrically 2-O-glucosylated. The degree of substitution at the 2-position, with α-D-Glcp, depends on the fermentation conditions; under optimized conditions greater than 80% 2-O-α-D-glucosylation was observed. The second polysaccharide is a heteroglycan with four monosaccharides in the repeat unit: residual signals in the NMR suggest that the sample also contains trace amounts (<3%) of cell wall polysaccharides.

Isolation and characterization of a high molecular mass ß-glucan from Lactobacillus fermentum Lf2 and evaluation of its immunomodulatory activity.

When grown in a semi-defined medium, L. fermentum Lf2 synthesizes significant quantities (∼2 g/L) of two exopolysaccharides (EPS). The two EPS were separated by preparative size exclusion chromatography to give a high molecular mass ß-glucan (1.23 × 106 Da) and a medium molecular mass heteroglycan (8.8 × 104 Da). The structure of the high molecular mass ß-glucan was determined using a combination of NMR spectroscopy, monomer and linkage analysis. The EPS has the following structure: The immunomodulatory activity of the high molecular mass EPS was studied in peripheral blood mononuclear cells (PBMC). Exposure of PBMC to an aqueous solution of the EPS for 24 h led to increased cell proliferation, changes in expression of the cytokines CD14 and TLR2, and to an increase in production of TNF-α compared to controls. In contrast, when cells that had been treated with EPS for 24 h and from which the EPS had been removed, were subsequently exposed to the bacterial antigen LPS very low levels of TNF-α production were observed. This result indicates that the EPS imparts immunotolerance in PBMC. An ability to modulate the release of the proinflammatory mediators, such as TNF-α, is an important goal in the development of therapies for the treatment of diseases, such as Crohn's disease and ulcerative colitis, associated with excessive release of inflammatory mediators.

Draft Genome Sequence of Lactobacillus fermentum Lf2, an Exopolysaccharide-Producing Strain Isolated from Argentine Cheese.

Lactobacillus fermentum Lf2, an Argentine cheese isolate, can produce high concentrations of exopolysaccharides (EPS). These EPS were shown to improve the texture and rheology of yogurt, as well as to play a protective role in mice exposed to Salmonella enterica serovar Typhimurium. Three gene clusters potentially involved in EPS production were identified in different locations of the L. fermentum Lf2 genome.

Exopolysaccharide from Lactobacillus fermentum Lf2 and its functional characterization as a yogurt additive.

Lactobacillus fermentum Lf2 is a strain which is able to produce high levels (approximately 1 g/l) of crude exopolysaccharide (EPS) when it is grown in optimised conditions. The aim of this work was to characterize the functional aspects of this EPS extract, focusing on its application as a dairy food additive. Our findings are consistent with an EPS extract that acts as moderate immunomodulator, modifying s-IgA and IL-6 levels in the small intestine when added to yogurt and milk, respectively. Furthermore, this EPS extract, in a dose feasible to use as a food additive, provides protection against Salmonella infection in a murine model, thus representing a mode of action to elicit positive health benefits. Besides, it contributes to the rheological characteristics of yogurt, and could function as a food additive with both technological and functional roles, making possible the production of a new functional yogurt with improved texture.

Technological, rheological and sensory characterizations of a yogurt containing an exopolysaccharide extract from Lactobacillus fermentum Lf2, a new food additive.

Lactobacillus fermentum Lf2, an autochthonous strain isolated as a non starter culture in Cremoso cheese, produces high EPS levels (~1g/L) in optimized conditions (SDM broth, pH6.0, 30°C, 72h). Technological (texture profile and rheological analysis) and sensory properties of non-fat yogurts with 300 and 600mg EPS/L were studied at 3 and 25days after manufacture. Yogurts with different EPS concentrations showed higher hardness values than the control group at both periods of time, being the only significant difference that remained stable during time. The consistency index was also higher for the treated samples at both times evaluated, being significantly different for samples with 300mg/L of EPS extract, while the flow behavior index was lower for EPS-added yogurts. The thixotropic index was lower (P<0.05) for samples with the highest EPS extract concentration at the end of the storage time. Regarding the sensory analysis, those yogurts with 600mg/L of EPS extract presented the highest values of consistency at 3days of storage. No considerable differences for defects (milk powder, acid, bitter and cooked milk flavors) were perceived between treated and control samples at both times evaluated. Syneresis was also studied and samples with 600mg/L of EPS extract presented the lowest syneresis values at 25days of storage, which considerably decreased with the time of storage. In conclusion, the EPS from L. fermentum Lf2, used as an additive, provided yogurt with creamy consistency and increased hardness, without the presence of unwanted defects and improving the water holding capacity of the product. All the analysis done showed the potential of this extract to be used as a technofunctional natural ingredient, and it should be considered its positive impact on health, according to previous studies.