Abstract: The production of fructooligosaccharides from sucrose by the enzyme glucose oxidase was done for 72 hours. In order to determine the relationship between enzyme activity and transformation of sucrose into fructooligosaccharides, the transfructosylating and hydrolyzing activities in the cell and culture both of microorganisms, including Aspergillus niger ATCC 20611, were assayed. The optimum conditions for reaction were as follows: pH, 5.5; temperature, 40oC; sucrose concentration, 70% (700g/L), agitation speed, 260 rpm. Products were analyzed by high performance liquid chromatograph (HPLC).