A newly isolated strain, TIT-90076, which produces beta-fructofuranosidase (FFase, EC 3.2.1.26) with a high transfructosylating activity was identified as Aspergillus japonicus. The optimal conditions for the enzymatic transfructosylating reaction occur at pH 5.0 and 55 degrees C. Sucrose is the best carbon source and yeast extract the best nitrogen source for enzyme production. Addition of MgSO . 7H(2)O and K2HPO4 shifted the morphology of 4 the fungal growth fi-om filamentous to pellet form; however, these salts did not affect FFase production. Antifoam-289 was the best additive for enzyme production among the polymeric and surfactant additives investigated. A central composite experimental design (CCD) and response surface methodology (RSM) were employed to derive a statistical model for the effects of sucrose and yeast extract on FFase production, and an initial concentration of 26.6% sucrose and 2.6% yeast extract was found to be optimal for the final enzyme production in batch cultures.