Screening and characterization of Lactobacillus strains producing large amounts of exopolysaccharides

A total of 182 Lactobacillus strains were screened for production of extrac ellular polysaccharides (EPS) by a new method: growth in liquid media with high sugar concentrations. Sixty EPS-positive strains were identified; 17 s trains produced more than 100 mg/l soluble EPS. Sucrose was an excellent su bstrate for abundant EPS synthesis. The ability to produce glucans appears to be widespread in the genus Lactobacillus. The monosaccharide composition of EPS produced by Lactobacillus reuteri strain LB 121 varied with the gro wth conditions (solid compared to liquid medium) and the sugar substrates ( sucrose or raffinose) supplied in the medium. Strain LB 121 produced both a glucan and a fructan on sucrose, but only a fructan on raffinose. This is the first report of fructan production by a Lactobacillus species. EPS prod uction increased with increasing sucrose concentrations and involved extrac ellular sucrase-type enzymes.