Physicochemical and rheological properties of some exopolysaccharides produced by lactic acid bacteria isolated from plant origin materials

Lactic acid bacteria (LAB) isolated from different plant-origin materials were screened for their ability to produce exopolysaccharides (EPS). The taxonomic affiliation of the EPS-producing strains was determined on the basis of their 16S rRNA sequences. Nine of the 146 tested strains have been shown to produce EPS in MRS medium with sucrose, all belonging to Leuconostoc mesenteroides species. One strain, namely L. mesenteroides 109, has been shown to produce large amounts of EPS, of about 19 g/L. All isolated EPS have a high molecular mass, of above 1400 kDa, and a monomer composition dominated by the presence of glucose. The rheological properties and the EPS production in different growth media were studied for four LAB strains producing high amounts of EPS, L. mesenteroides 109, 112, 124, 127, and one strain, namely Weissella cibaria 120, which was not able to produce EPS when grown in MRS with sucrose. Among the EPS producing strains, the most promising one regarding the potential application in the food industry is L. mesenteroides 109, as it produces considerable amounts of EPS (over 25 g/l), together with a high viscosity (over 2400 mPa s) in soy milk supplemented with sucrose.