Response surface method (RSM) is a recent common method used to identify culture condition for optimal production of particular metabolite. In the present study, RSM is used to optimize a catalytic reaction in levan production by heterologous expression of lsbl-bk2 gene isolated from halophilic bacteria Bacillus licheniformis. Levan is a polyfructose polymer produced from sucrose by the action of extracellular levansucrase secreted by the microorganism. Three factors for levan production, namely sucrose concentration, pH, and temperature of reaction were optimized by full factorial and central composite designs in RSM. The result indicated that the optimum in vitro condition for levan production was achieved when the levansucrase catalytic reaction was performed at 32°C, pH 8, in 12% (w/v) sucrose solution. Levan produced by this procedure was verified by FTIR and NMR spectroscopies.