Levan, a polysaccharide from Zymomonas mobilis, was hydrolyzed to obtain oligofructans or fructooligosaccharides with a degree of polymerization varying from 4 to 14. Fructooligosaccharides (FOS) are short chain fructans that beneficially affects the host by selective stimulation of growth and activity of one or a number of bacteria including probiotic bacteria in the colon. The hydrolysis was performed in a microwave oven to shorten the reaction time. The experiments showed that it is possible to maximize selected oligomers by interrupting the hydrolysis at the due time. The results allow one to infer that the procedure may also be useful for production of oligomers from other polysaccharides. (C) 2007 Elsevier Ltd. All rights reserved.