Production and structural characterization of exopolysaccharides from newly isolated probiotic lactic acid bacteria

In this work, four exopolysaccharide-producing lactic acid bacteria (LAB) strains, newly isolated fromTunisian spontaneously fermented foods and beverages, namely bovine and turkey meat sausages(BMS and TMS), date palm sap (DPS) and cow milk (CM), were identified as Leuconostoc citreum-BMS,Leuconostoc mesenteroides-TMS, Pediococcus pentosaceus-DPS and Leuconostoc pseudomesenteroides-CM,respectively. The isolated strains showed the ability to withstand simulated human gastrointestinal (GI)tract conditions (low pH, lysozyme, bile salts, pepsin and pancreatin) and showed high surface hydropho-bicity (79–90%), besides their ability to act against Escherichia coli and Listeria monocytogenes and toproduce exopolysaccharides (EPS). Therefore, these isolates can be served as potential probiotics. The pro-duced EPS were growth-associated suggesting that they are primary metabolites. The molecular weightswere higher than 106Da using HPLC-SEC. 2D-NMR results indicated that all the samples were mixtures ofdextran and levan, except for EPS-CM which was a levan-type EPS. Furthermore, the EPS samples showedan abitlity to inhibit and to disrupt pathogenic biofilms and showed high thermostability studied via dif-ferential scanning calorimetry (DSC) with melting points higher than 224◦C making them promising tobe used in thermal processed foods.