Isolation of exopolysaccharide-producing bacteria and yeasts from Tibetan kefir and characterisation of the exopolysaccharides

Fifteen organisms were isolated from Tibetan kefir. Six of them were exopolysaccharide (EPS)-producing strains cultured in skim milk medium, which included two yeasts (Kazachstania unispora), one acetic acid bacterium (Acetobacter okinawensis) and three lactic acid bacteria (Leuconostoc pseudomesenteroides). The protein oxidative damage protection assay revealed that preincubation of exopolysaccharides (EPSs) could restore the levels of protein oxidation in a dose-dependent manner. The SEM images indicated that there were great differences in the microstructures and surface morphologies among the EPSs. The GC analysis of the EPSs showed that all of the EPSs were composed of more than one kind of monosaccharide.