Continuous production of fructooligosaccharides (FOS) by Aureobasidium pullulans immobilized on calcium alginate beads with a packed bed was investigated at a plant scale reactor. Optimum conditions were with 770 g sucrose/l, being fed at 200 l/h at 50 degrees C which gave a productivity of 180 g FOS/l h. Initial activity was maintained for more than 100 days. The reactor was successfully scaled up to a production scale of 1.2 m(3).