African Journal of Biotechnology Vol. 6 (22), pp. 2603-2611, 19 November 2007   

ISSN 1684–5315 © 2007 Academic Journals        

Full Length Research Paper

Characterization of the exopolysaccharide produced by a whey utilizing strain of Klebsiella oxytoca

Dlamini Abednego M.¹*, Peiris Paul S.², Bavor John H.² and Kailasapathy Kasipathy³

¹Department of Animal Production and Health, University of Swaziland, Private bag Luyengo, Luyengo, Swaziland.

²School of Natural Science, University of Western Sydney – Hawkesbury, Bourke Street, Richmond, NSW 2753 Australia.

³Centre for Plant and Food Research, University of Western Sydney – Hawkesbury, Bourke Street, Richmond, NSW 2753 Australia.

*Corresponding author. E-mail: adlamini@agric.uniswa.sz, Tel.: +268 5274021; Fax: +268 5274441.

Accepted 20 August, 2007

Physical, chemical and rheological properties of a polysaccharide produced by an isolate of Klebsiella oxytoca were characterized. Freeze dried samples of the polysaccharide were neutral and were completely soluble in water. Samples did not form gels even in the presence of salt treatments. The major monosaccharide constituents of the polysaccharide were rhamnose (37%, w/w) and glucose (34%, w/w). Residues of cellobiose were detected, suggesting that the polysaccharide had a cellulose backbone. The gum was more comparable to broth apparent viscosities of xanthan gum than to gellan gum. The K. oxytoca polysaccharide (KOP) produced high solution viscosity at low concentrations. At a gum concentration 0.5% (w/v), an apparent viscosity of 400 cP at 24 s^-1 was obtained. Rheological behavior showed that the KOP formed non newtonian fluids, indicating that it is a pseudoplastic biopolymer. Although the KOP solutions displayed pseudoplastic behavior, increases in shearing time did not result in significant changes on the apparent viscosity. This indicated that the gum is neither thixotropic nor rheopectic. The conclusion reached about the potential application of the gum was that it could be suitable for use as a stabilizing or suspending agent rather than a gelling agent.

Key words: Apparent viscosity, exopolysaccharide, Klebsiella oxytoca, pseudoplastic, rheology, rhamnose, whey.