Separation, purification and characterisation of extracellular polysaccharides produced by slime-forming Lactococcus lactis ssp cremoris strains

Five slime-forming Lactococcus lactis ssp. cremoris strains (ARH53, ARH74, ARH84, ARH87 and B30) isolated from Finnish fermented milk viili have been shown to produce viscous exopolysaccharides (EPSs) in skim milk cultures. T he EPSs were separated and purified by treatment with trichloroacetic acid, ethanol precipitation and dialysis. All EPSs were anionic and composed of galactose, glucose and rhamnose of similar ratios. The H-1 NMR spectrum of the EPS of strain ARH74 showed high similarity with that of strain SBT 0495 EPS, previously reported to consist of pentasaccharide repeating units wit h a phosphodiester structural element. In dilute aqueous solutions (up to 0 .1 g dl(-1) of EPS), the EPSs showed polyelectrolyte effects, and they diff ered in viscosity. At a higher concentration of EPS (1%, w/v), the EPS solu tion showed a shear thinning behaviour, and the viscosity was temperature, pH and salt dependent. Addition of 1% EPS (w/v) to skim milk resulted in a significant increase in viscosity, and a gel formed at 40 degrees C. (C) 19 99 Elsevier Science Ltd. All rights reserved.