This study attempted to establish an efficient biosensor for the aspartame determination in soft drinks and commercial sweetener tablets. The sensor was a bienzyme system composed of carboxyl esterase and alcohol oxidase, immobilized in gelatin membrane, subsequently combined with the dissolved oxygen electrode. The optimum operational conditions for the enzyme sensor were pH 8.0 and 37 degreesC. A linear relationship was observed between dissolved oxygen (D.O) consumption and the aspartame concentrations in the range of 5.0 x 10(-8) and 4.0 x 10(-7) M. One assay could be completed within 10 minutes. In the case of aspartame determination in commercial soft drinks and sweetener tablets by this system, the results were found to be in close agreement with the labeled values provided by manufacturer. (C) 2003 Elsevier Ltd. All rights reserved.