Development of an improved procedure for isolation and purification of exopolysaccharides produced by Lactobacillus delbrueckii subsp. bulgaricus NCFB 2483.

A method was developed for the isolation and purification of exopolysaccharide (EPS) produced by Lactobacillus delbrueckii subsp. bulgaricus NCFB 2483 that can be adapted for industrial-scale operation. Hydrolyzed milk medium, which was ultrafiltered to remove molecular species larger than 2.5 x 10(5) Da, was found to be a suitable growth medium for the bacteria, which produced approximately 400 mg EPS/l . Optimal isolation of EPS was achieved using centrifugation, filtration and ethanol precipitation methods. Insoluble and soluble EPS fractions were obtained. The soluble fraction was purified using a series of ethanol precipitations to achieve approximately 98% (w/w) purity. This fraction consisted of galactose, glucose, rhamnose and mannose in the ratio of approximately 5:1:0.6:0.5, with traces of glucosamine.