New Bacterial Polysaccharide from Arthrobacter

Abstract

A bacterial strain (NRRL B-1973) isolated from soil at Guatemala City and tentatively identified as an Arthrobacter species produced a polysaccharide with unusual properties. Conditions were studied for the production of this microbial gum in shaken flasks and 20-liter fermentors. Suitable nutrients for optimal polysaccharide production included 3% glucose, 0.3% enzyme-hydrolyzed casein, magnesium sulfate, manganese sulfate, and potassium phosphate buffer (pH 7.0). Polysaccharide yields ranged from 40 to 45%, based on initial dextrose in the medium in 3- or 4-day fermentations. The gum was readily recovered from culture fluid by alcohol precipitation in the presence of an electrolyte. The Arthrobacter gum exhibited characteristics unique for a polyelectrolyte. Viscosity of solutions was not decreased by heating in the presence of salt, and the gum withstood a temperature of 121 C for 30 min. At polysaccharide levels above 0.75%, gels were formed when solutions were autoclaved with KCl. There was no significant change in viscosity over a pH range of 5.0 to 10.0.