Fructo-oligosaccharides (FOS) can be produced by the action of fructosyl transferases from plants and microorganisms. The production of FOS was attempted using culture fluid, cells and culture broth homogenate from Aspergillus oryzae CFR 202 and Aureobasidium pullulans CFR 77 using different concentrations of sucrose as substrate. The maximum yield of FOS obtained using A. oryzae CFR 202 culture fluid was 50-54% after a reaction time of 12 h at 55 degreesC at sucrose concentrations of 55% (w/v) and 80% (w/v). The culture broth of A. oryzae CFR 202 gave 50-53% FOS after 12 h of reaction when 55% (w/v) sucrose was used as substrate. Although the cells were not suitable for FOS production, the culture fluid and culture broth homogenate of A. pullulans CFR 77 gave a conversion yield of up to 57% from sucrose at concentrations of 55 and 80% (w/v). (C) 2003 Elsevier Ltd. All rights reserved.