A yeast strain (XS1) capable of selective utilization of fructooligosaccharides (FOSs) syrup was identified as Wickerhamomyces anomala. Cells of W. anomala XS1 were immobilized in calcium alginate and incubated with an FOS mixture at 30 degrees C. The purity of the FOS increased from 54.4% to 80.1% (w/w) as 93.6% of monosaccharides were metabolized while the oligosaccharides were not affected. The immobilized yeast cells could be recycled 10 times and the corresponding batch treatments achieved FOS purities around 80%. Thus, the method could be promising for large-scale purification of FOS syrup at low cost. A byproduct formed by the yeast was identified as ethyl beta-D-fructofuranoside by MS and NMR spectroscopy. (C) 2012 Elsevier Ltd. All rights reserved.