Invertase has a vital role in ethanol fermentation, especially on sucrose-containing media. In this study, catabolite-resistant mutants of Saccharomyces cerevisiae were isolated through gamma ray mutagenesis with improved productivity of ethanol and invertases. Enzyme productivity of mutant yeast was compared with that of the parent. Various fermentation parameters were optimized, including substrate concentration, pH, and temperature on the production of invertase and ethanol. Applying optimized conditions (pH 4.6, 37ºC) at lab scale, industrial scale experiments in 300 m³ fermenters were performed. Mutants had completed fermentation with high efficiency in 28 hrs irrespective of parents that took 36 hrs. The mutant obtained is of great commercial value as it has the potential to enhance the overall profitability of the fermentation process through advancement in the quality of the final product.