Exopolysaccharide and Kestose Production by <i>Lactobacillus sanfranciscensis</i> LTH2590

<jats:title>ABSTRACT</jats:title> <jats:p> The effect was investigated of sucrose concentration on sucrose metabolism and on the formation of exopolysaccharide (EPS) by <jats:italic>Lactobacillus sanfranciscensis</jats:italic> LTH2590 in pH-controlled fermentations with sucrose concentrations ranging from 20 to 160 g liter <jats:sup>−1</jats:sup> . The EPS production increased and the relative sucrose hydrolysis activity decreased by increasing the sucrose concentration in the medium. The carbon recovery decreased from 95% at a sucrose concentration of 30 g liter <jats:sup>−1</jats:sup> to 58% at a sucrose concentration of 160 g liter <jats:sup>−1</jats:sup> because of the production of an unknown metabolite by <jats:italic>L. sanfranciscensis</jats:italic> . This metabolite was characterized as a fructo-oligosaccharide. The oligosaccharide produced by <jats:italic>L. sanfranciscensis</jats:italic> was purified and characterized as a trisaccharide with a glucose/fructose ratio of 1:2. The comparison of the retention time of this oligosaccharide and that of pure oligosaccharide standards using two different chromatography methods revealed that the oligosaccharide produced by <jats:italic>L. sanfranciscensis</jats:italic> LTH2590 is 1-kestose. Kestose production increased concomitantly with the initial sucrose concentration in the medium. </jats:p>