Characterization of a β-fructofuranosidase from Schwanniomyces occidentalis with transfructosylating activity yielding the prebiotic 6-kestose

β-Fructofuranosidases are powerful tools in industrial biotechnology. We have characterized an extracellular β-fructofuranosidase from the yeast Schwanniomyces occidentalis. The enzyme shows broad substrate specificity, hydrolyzing sucrose, 1-kestose, nystose and raffinose, with different catalytic efficiencies (kcat/Km). Although the main reaction catalysed by this enzyme is sucrose hydrolysis, it also produces two fructooligosaccharides (FOS) by transfructosylation. A combination of 1H, 13C and 2D-NMR techniques shows that the major product is the prebiotic trisaccharide 6-kestose. The 6-kestose yield obtained with this β-fructofuranosidase is, to our concern, higher than those reported with other 6-kestose-producing enzymes, both at the kinetic maximum (76 g l−1) and at reaction equilibrium (44 g l−1). The total FOS production in the kinetic maximum was 101 g l−1, which corresponded to 16.4% (w/w) referred to the total carbohydrates in the reaction mixture.