PRODUCTION OF A NOVEL EXTRACELLULAR POLYSACCHARIDE BY LACTOBACILLUS-SAKE 0-1 AND CHARACTERIZATION OF THE POLYSACCHARIDE

A novel exopolysaccharide (EPS) produced by Lactobacillus sake 0-1 (CBS 532.92) has been isolated and characterized. When the strain was grown on glucose, the produced EPS contained glucose and rhamnose in a molar ratio of 3:2 and the average molecular mass distribution (M(m)) was determined at 6 x 10(6) Da. At a concentration of 1%, the 0-1 EPS had better viscosifying properties than xanthan gum when measured over a range of shear rates from 0 to 300 s(-1), while shear-thinning properties were comparable. Rheological data and anion-exchange chromatography suggested the presence of a negatively charged group in the EPS. Physiological parameters for optimal production of EPS were determined in batch fermentation experiments. Maximum EPS production was 1.40 g . liter(-1), which was obtained when L. sake 0-1 had been grown anaerobically at 20 degrees C and pH 5.8. When cultured at lower temperatures, the EPS production per gram of biomass increased from 600 mg at 20 degrees C to 700 mg at 10 degrees C but the growth rate in the exponential phase decreased from 0.16 to 0.03 g . liter(-1). h(-1). EPS production started in the early growth phase and stopped when the culture reached the stationary phase. Growing the 0-1 strain on different energy sources such as glucose, galactose, mannose, fructose, lactose, and sucrose did not alter the composition of the EPS produced.