AN ANIONIC GALACTOMANNAN POLYSACCHARIDE GUM FROM A NEWLY-ISOLATED LACTOSE-UTILIZING BACTERIUM .2. FERMENTATION KINETICS AND LACTOSE TRANSPORT

The facultative bacterium Erwinia ATCC 55046, isolated from the soil of a whey-treated farm field, produces an anionic galactomannan polysaccharide gum (designated lactan gum) from lactose and other sugars. On lactose semidefined medium in a 5-L fermentor, the organism had a maximum growth rate of 0.66 h-1 and produced 26 g/L polysaccharide with a yield on lactose of 0.66 g/g and a volumetric productivity of 0.6 g/(L.h). In shake flasks, the best final gum concentration was obtained with a carbon to nitrogen ratio of 40:1 (w/w). Gum yield and concentration was greater on disaccharides than on monosaccharides. The organism was found to transport lactose by a permease system as opposed to a phosphotransferase system. Lactan gum can be produced efficiently from lactose, the major sugar in whey and whey permeate.