To date, the physical properties including the morphology, thermal characteristics, and emulsifying activities of a single sugar a-linked glucuronic acid-based water-soluble oligosaccharides (WSOS) produced by Gluconacetobacter hansenii PJK have not been investigated or published elsewhere. Therefore, the current study was undertaken to investigate these important physical properties of WSOS. Field-emission scanning electron microscopy of the WSOS revealed a porous flake-type structure free from adhered bacterial cells. The degradation of the WSOS occurred by four well-differentiated steps with a maximum weight loss (similar to 40%) in a range of 230-300 degrees C. The pyrolysis temperature of the WSOS was found to be 278 degrees C with an enthalpy of 83.01 J/g. The emulsification ability of the WSOS increased initially with concentration, followed by a decrease, and finally became constant. The optimum concentration of WSOS for maximum emulsification (emulsifying ability) was 0.15% (w/v). The emulsions prepared with WSOS did not exhibit significant stability. The formation of oil and aqueous layers was initiated just after 2 min for emulsion prepared with 0.15% (w/v) WSOS, which completely separated after 24 h. It is concluded that WSOS has thermal stability comparable to other microbial polysaccharides. They have moderate emulsification properties, which may be due to the oligomeric nature of WSOS. Additionally the producer organism of WSOS is non-pathogenic. Therefore, the produced WSOS have potential applications in food and/or pharmaceutical preparations and as therapeutic agent in biomedical fields. (c) 2006 Elsevier Ltd. All rights reserved.