抄録
Lyophilized extracellular mucilage (LEM) powder was recovered from Klebsiella oxytoca CF154 culture, and the yield was approximately 0.8g per liter of the culture medium. Relative viscosity (RV) increased as the concentration 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 over a pH range of 4 to 9, although it dropped sharply outside of this range. The higher NaCl concentration (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°C. Changes in molecular flexibility, which was indicated as changes in activation energy of 0.2% LEM solution, depended on temperature. Results from Sephacryl S-400 gel permeation chromatography (GPC) indicate that LEM is a mixture of protein-polysaccharide complexes of which the dominant fraction (85%) has a molecular weight ranging from 1.5-1.8 MDa in the polysaccharide moiety. HPLC analysis suggested that the major sugars in this dominant fraction were mannose, galactose, glucose, and arabinose. In addition, there exists uronic acid at 6.3% in this dominant fraction.
