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Functional role of exopolysaccharides biosynthesized by Lactobacillus fermentum D12 in strain´s probiotic activity

An autochthonous fresh smoked cheese isolate, identified by whole genome sequencing (WGS) as Lactobacillus fermentum D12, has been shown as highly exopolysaccharides (EPOLs) producing strain, where the value of EPOLs production reaches 200.25 mg/L. High Performance Size Exclusion Chromatography (HPSEC), 1H-NMR, GC and GC-MS analysis revealed that this strain produces three different types of EPOLs ; one homopolysaccharide with a molecular weight of 400 kDa and two different heteropolysaccharides with molecular weight lower than 2 kDa. 2D-NMR spectroscopy analysis revealed that EPOLs, with the highest molecular mass, is composed of repeating units of D-glucose linked by an α-1, 4-glycosidic bond, where 20 % of the glucose subunits is acetylated at C-3. Since EPOLs synthesized by probiotic lactobacilli have been recognized as probiotic functional macromolecules, the potential role of these three EPOLs in the probiotic activity of Lb. fermentum D12 strain was evaluated. Strain survival in rigorous gastrointestinal (GI) conditions is the main criteria to be addressed during probiotic selection. Considering that D12 strain efficiently survives simulated gastrointestinal tract conditions (bacteria counts ≥106 CFU ml-1), the potential protective effect of EPOLs was evaluated. Hereof, to further define the functionality of EPOLs in probiotic properties of Lb. fermentum D12 their role in autoaggregation, adhesion to mucin, extracellular matrix (ECM) proteins fibronectin, laminin and collagen and human enterocyte-like epithelial Caco-2 cell line is tested. Moreover, since these macromolecules can be bound and/or released to extracellular medium, there potential as surface protective coat will be assessed through determination of Lb. fermentum D12 bacterial cell viability during freeze-drying, which is one of the most convenient methods for probiotic bacteria maximal survival and recovery.

exopolysaccharides, probiotic activity, adhesion, protective role, freeze-drying

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