Composition and rheological properties of extracellular mucilage from marine bacterium Klebsiella oxytoca CF154

Lyophilized extracellular mucilage (LEM) powder was recovered from Klebsiel la oxytoca CF154 culture, and the yield was approximately 0.8 g per liter o f the culture medium. Relative viscosity (RV) increased as the concentratio n of LEM aqueous solution increased from 0.0 to 0.5%. Factors affecting RV of 0.2% LEM solution showed that the RV was stable Dyer a pH range of 4 to 9, although it dropped sharply outside of this range. The higher NaCl conce ntration (0-5%) in LEM solutions was, the lower RV of LEM solutions was. RV of 0.2% LEM solution decreased as the temperature increased from 10 to 80 degrees C. Changes in molecular flexibility, which was indicated as changes in activation energy of 0.2% LEM solution, depended on temperature. Result s from Sephacryl 5-400 gel permeation chromatography (GPC) indicate that LE M is a mixture of protein-polysaccharide complexes of which the dominant fr action (85%) has a molecular weight ranging from 1.5-1.8 MDa in the polysac charide moiety, HPLC analysis suggested that the major sugars in this domin ant fraction were mannose, galactose, glucose, and arabinose. In addition, there exists uronic acid at 6.3% in this dominant fraction.