Exopolysaccharide-producing Lacticaseibacillus paracasei strains isolated from kefir as starter for functional dairy products

BENGOA, ANA AGUSTINA; DUEÑAS, MARÍA TERESA; PRIETO, ALICIA; GARROTE, GRACIELA L.; ABRAHAM, ANALÍA G.

Frontiers in Microbiology

Frontiers media SA

Año: 2023 vol. 14

Exopolysaccharides (EPS) produced by lactic acid bacteria are molecules of greatinterest for the dairy food industry. Lacticaseibacillus paracasei CIDCA 8339,CIDCA 83123, and CIDCA 83124 are potentially probiotic strains isolated fromkefir grains whose EPS-production on MRS broth is dependent on incubationtemperature. The aim of the present work is to evaluate the effect of fermentationtemperature on the characteristics of EPS produced in milk by L. paracasei strainsand the consequent impact on the rheological properties of the fermentedproducts. Additionally, the protective effect of these EPS against Salmonellainfection was evaluated in vitro. Acid gels with each strain were obtained by milkfermentation at 20°C, 30°C, and 37°C evidencing for all the strains a reductionin growth and acidification rate at lower temperature. Lacticaseibacillusparacasei CIDCA 83123 showed low fermentation rate at all temperaturesrequiring between 3 and 8 days to obtain acids gels, whereas CIDCA 8339 and83124 needed between 24 and 48 h even when the temperature was 20°C.Fermentation temperature led to changes in crude EPS characteristics of thethree strains, observing an increase in the relative amount of the high molecularweight fraction when the fermentation temperature diminished. Additionally,EPS83124 and EPS83123 presented modifications in monosaccharide composition,with a reduction of rhamnose and an increase of amino-sugars as temperaturerise. These changes in the structure of EPS83124 resulted in an increase of theapparent viscosity of milks fermented at 20°C (223 mPa.s) and 30°C (217 mPa.s)with respect to acid gels obtained at 37°C (167 mPa.s). In order to deepen theknowledge on EPS characteristics, monosaccharide composition of low and highmolecular weight EPS fractions were evaluated. Finally, it was evidenced that thepreincubation of intestinal epithelial cells Caco-2/TC-7 with EPS8339 and EPS83124partially inhibit the association and invasion of Salmonella. In light of these results,it can be concluded that the selection of the EPS-producing strain along with theappropriate fermentation conditions could be an interesting strategy to improvethe technological properties of these L. paracasei fermented milks with potentialprotective effects against intestinal pathogens.