Exopolysaccharide (EPS)-producing lactic acid bacteria are used in the dairy industry to obtain products with appropriate sensorial properties. Specific EPS act as stabilizers, thickeners, and/or fat-replacers, and are considered as natural biopolymers. The autochthonous microbiota of foods provides a rich reservoir of biodiversity to find biopolymers for novel applications. In this study, a collection of LAB isolated from homemade Algerian dairy products was screened for a rational selection of EPSproducing strains. Six isolates, identified as Lactobacillus plantarum, presented a stable mucoid/ropy phenotype after several sub-cultivations and they were used to ferment skimmed milk. Those fermented with strains LBIO1 and LBIO28 had higher viscosity, a smooth/ creamy texture and presented lower syneresis. The kinetics of growth and EPS-production, followed for 48 h, showed that both strains had similar behaviour, the molar mass (about 2x10 6 Da) and radius of gyration (about 80 nm) of the polymers being also similar. However, LBIO28 was able to increase the apparent viscosity of the fermented milk to a higher extent than LBIO1, which could be related with the earlier accumulation of EPS in the first strain in relation to the gelation point. Thus, these two ropy EPS-producing strains are suitable for different applications in dairy fermentations.

The exopolysaccharide (EPS)-producing Lactobacillus plantarum (renamed as Lactiplantibacillus plantarum) LBIO1, LBIO14 and LBIO28 strains, isolated from fermented dairy products typical from Algeria, were characterized to evaluate the impact of the polymers in milk fermentations. Their genomes revealed the presence of two complete eps clusters of the four described for the reference strain WCFS1. Besides, the three strains presented identical sequences of eps3 and eps4 clusters, but LBIO1 and LBIO28 harbour three genes belonging to eps2 which are absent in the LBIO14 genome. The EPS purified from fermented skim-milks manufactured with the strains showed identical nuclear magnetic resonance (1H-NMR) and size exclusion chromatography coupled with a multiangle laser light scattering detector (SEC-MALLS) profiles for polymers LBIO1 and LBIO28, whereas LBIO14 EPS was different due to the lack of the high-molecular weight (HMW)-EPS and the absence of specific monosaccharide’s peaks in the anomeric region of its proton NMR spectrum. The presence of the HMW-EPS correlated with optimal sensorial-physical characteristics of the fermented skim-milks (ropy phenotype). Their microstructures, studied by confocal scanning laser microscopy (CSLM), also showed differences in the organization of the casein-network and the distribution of the bacteria inside this matrix. Therefore, the strain LBIO1 can be proposed for the manufacture of dairy products that require high whey retention capability, whereas LBIO28 could be applied to increase the viscosity.