This study aimed to investigate metabolic changed related to glucose – repression by the analysis of ethanol productivity which is mainly affected by the glucose effect. Five parental isolates and 15 genotypes derived from three crosses were used in this study to be evaluated for heterosis of ethanol productivity. Bioethanol produced can contribute to a cleaner environment using a cheap substrates such as sugarcane juice sub – products used in this study . Mating between yeast isolates gave different recombinant genotypes some of them showed glucose – repressed or depressed to higher concentrations  of sugarcane juice sub – products. Sugar repression is one of the major limitations in the fermentation of cost – effective ethanol productivity . When the hybrid genotypes were grown in a culture containing 0.02 sub – products they are exhibited positive hybrid vigor for ethanol production overall the genotypes compared to the mid – parents. All hybrids exhibited negative heterosis when they were cultivated in the culture containing 0.04 sub – products, indicating that they were glucose – sensitive due to glucose pulses at this concentration. In addition, when the hybrids resulted from the cross between p₁ x p₄ were grown in a fermentation culture containing 0.06 sub – products they are also exhibited negative heterosis for ethanol productivity. In contrast, all the hybrids derived from the crosses between p₂ x p₅ and p₃ x p₅ overcoming glucose repression of 0.06 sub – products containing medium because heterosis seemed to appear at this level of carbohydrates.