International Journal of Biological Macromolecules 48 (2011) 695–699 Contents lists available at ScienceDirect International Journal of Biological Macromolecules journal homepage: www.elsevier.com/locate/ijbiomac Influence of temperature on the rheological behavior of a new fucose-containing bacterial exopolysaccharide Madalena Cruz a , Filomena Freitas a , Cristiana A.V. Torres a , Maria A.M. Reis a , Vítor D. Alves b,∗ a REQUIMTE/CQFB, Chemistry Department, FCT/Universidade Nova de Lisboa, 2829-516 Caparica, Portugal b CEER-Biosystems Engineering, Institute of Agronomy, Technical University of Lisbon, Tapada da Ajuda, 1349-017 Lisbon, Portugal article info Article history: Received 12 November 2010 Received in revised form 15 February 2011 Accepted 21 February 2011 Available online 3 March 2011 Keywords: Rheology Microbial polysaccharide Temperature Enterobacter sp. abstract The effect of temperature on the rheology of a new fucose-containing extracellular polysaccharide (EPS) was evaluated. The steady state data revealed a shear-thinning behavior, with the viscosity being imme- diately recovered when the shear rate was decreased. The mechanical spectra indicated viscous solutions with entangled polymer molecules in the range of temperatures studied (from 15 ◦ C to 65 ◦ C). In addi- tion, the Time–Temperature Superposition principle was successfully applied and the Cox–Merz rule was valid, reinforcing the idea of a thermorheologically simple behavior for the EPS in aqueous solution. Furthermore, the viscous and viscoelastic properties at 25 ◦ C were maintained after consecutive heating and cooling cycles, indicating a good thermal stability under temperature fluctuations. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Polysaccharides have a wide range of applications, including food, pharmaceutical, cosmetics, paints, explosives, paper and oil industries, due to their diverse structures and physical proper- ties. They are extensively used as thickening, gelling, stabilizing, binding, emulsifying and flocculating agents. Natural polysac- charide sources include plants (e.g. starch and pectins), algae (e.g. carrageenan, alginate and agar), animals (e.g. chitosan) and microorganisms (e.g. xanthan and gellan) [1]. However, produc- tion of polysaccharides by microbial fermentation has advantages in comparison to their extraction from other sources, since microor- ganisms usually exhibit higher growth rates and the manipulation of production conditions is much easier [2]. Unlike other sources, microbial fermentation is not influenced by climate changes or seasonality. Up to now, the main factor limiting commercial pro- duction of microbial polysaccharides is related to the high cost of the most commonly used substrates (e.g. glucose, starch and sucrose) [1]. Previous works on microbial polysaccharides production showed the potential of glycerol byproduct from the biodiesel production as sole carbon source. This byproduct is a low cost sub- strate, and its availability is increasing with the increase of biodiesel production. Using a Pseudomonas oleovorans strain, a galactose- rich polysaccharide was produced [3]. It was mainly composed by ∗ Corresponding author. Tel.: +351 21 3653546; fax: +351 21 3653200. E-mail address: vitoralves@isa.utl.pt (V.D. Alves). galactose, with variable amounts of mannose, glucose and rham- nose, depending on the cultivation conditions. It also contained acyl groups substituents (acetate, pyruvate and succinate). Its char- acterization, regarding solution properties, rheological behavior, emulsifying and flocculating capacities, as well as film-forming ability, have been reported [3–7]. Afterwards, a distinct novel exopolysaccharide (EPS), contain- ing fucose, has been produced by a newly isolated bacterial strain grown on glycerol byproduct. This strain has been identified and named Enterobacter A47 DSM 23139. Previous work was focused on the rheological and morphological characterization of the cul- ture broth during EPS production in the bioreactor [8]. That study was determinant for the evaluation of the factors affecting the broth viscosity over cultivation time, which is closely related with heat and mass transfer rates that eventually have an impact upon bioreactor’s productivity and yield. A preliminary polymer charac- terization in terms of its chemical composition, molecular weight and intrinsic viscosity has also been presented [9]. The functional properties of this fucose-containing EPS, including its rheological behavior in aqueous medium, emulsion forming and stabilizing capacity and flocculating activity, were compared to other commer- cially available polymers, namely, fucogel, xanthan gum, guar gum, alginate, pectin and carboxymethylcellulose (CMC), to evaluate its potential industrial applications. The characterization of the new fucose containing EPS contin- ued and, in the present work, the attention was driven to study the influence of temperature on the rheological properties of the fucose-rich EPS. A similar insight was already performed in a pre- vious work for the galactose-rich EPS produced by P. oleovorans 0141-8130/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.ijbiomac.2011.02.012