Rheological characterization under shear of a fraction of polymer produced via fermentation of whey-related media by Rahnella aquatilis

• Published in: Carbohydrate polymers Vol. 37; no. 1; pp. 1 - 6
• Main Authors: Pintado, M.E, Lopes da Silva, J.A, Pintado, A.I.E, Malcata, F.X
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 1998; Elsevier Science
• Subjects: Applied sciences; Bacteria; Composition effects; Exact sciences and technology; Fermentation; Ionic strength; Lactan; Natural polymers; pH effects; Physicochemistry of polymers; Polysaccharide; Rahnella aquatilis; Rheology; Shear flow; Solutions; Starch and polysaccharides; Viscosity; Rahnella aquatilis; Polysaccharide; Lactan; Shear flow; Experimental study; Fermentation; Whey; Property processing relationship; Whey by product; Microbial origin; Ionic strength; Concentration effect; Microorganism culture; pH; Bacteria; Oside polymer; Aqueous solution; Flow curve; Enterobacteriaceae
• ISSN: 0144-8617; 1879-1344
• DOI: 10.1016/S0144-8617(98)00032-0

Production of lactan, a polysaccharide composed of mannose, galactose and galacturonic acid (at the ratio of 5:3:2), starting from a semi-defined medium containing lactose via fermentation with Rahnella aquatilis was described previously. In this communication, such polysaccharide was produced from five alternative fermentation media: (1) a synthetic (defined) medium, plain whey (under (2) aerobic and (3) anaerobic conditions), (4) whey permeate and (5) whey with 2% NaCl (w/v). The effect of the concentration of polysaccharide, pH and ionic strength at harvest on the rheological properties of the polysaccharide was studied using lactan-enriched fractions recovered from each medium and analysed in solution under steady shear flow. Lactan solutions showed a shear-thinning behaviour in all cases, and increases in viscosity were observed at increasing concentrations of polysaccharide, as expected. The polysaccharide fraction produced from whey with 2% (w/v) NaCl and plain whey under anaerobic conditions exhibited lower viscosity than that produced from the other media, an observation that is associated with the lower concentration of polysaccharide. Post-harvest addition of salts (KCl or CaCl 2) and changes in pH (3–11) affected slightly the viscosity of the polysaccharide solutions.