Production of high-content fructooligosaccharides (FOSs) from sucrose using calcium alginate-immobilized mycelia of Aspergillus japonicus and Aspergillus niger in an internal-loop airlift bioreactor was investigated. The optimal entrapment of mycelia in A. japonicus and A. niger in calcium alginate were 1% and 7 % (w/w), respectively. When 60 g of the immobilized mycelia of A. japonicus was supplied into the reactor filling with 3-L 300 g/L sucrose solution and gas velocity 7.32 cm/s, the total FOS production was about 55% (w/w) of total sugars in the mixture after a batch reaction for 9 It. To remove the generated glucose, an inhibitor of beta-D-fructofuranosidase, the optimal input of the second immobilized A. niger mycelia particles was 315 g. With this input, the total FOSs mass fraction reached up to 90% (w/w) and the initial rate of transfructosylation was increased almost twice as without supplying glucose oxidase. In addition, 5.49 cm/s was suggested as the operating gas velocity for considering sufficient oxygen supply for glucose oxidase without generating excessive shear stress to damage the immobilized particles. (c) 2008 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.