Ethanol production, by a simultaneous saccharification and fermentation process (SSF) of native starch from corn flour, has been performed by Saccharomyces cerevisiae (Ethanol Red) and granular starch hydrolyzing enzyme (STARGEN 001). The quantitative effects of mash concentration, enzyme dose and pH were investigated by the use a Box?Wilson central composite design protocol. It was found that for native corn starch, maximum ethanol concentration of 110,36 g/l was obtained using a mash concentration of 25%, which resulted in ethanol yield of 85,71%. The optimum conditions for the above yield were found for the enzyme dose of 2,05 ml/kg and pH of 5.0. These results indicated that by using the central composite design, it is possible to determine accurate values of the fermentation parameters for maximum ethanol production.