A detailed study was conducted in terms of the influence of dissolved oxygen (DO) and growth temperature related to the endo-polygalacturonase synthesis by the yeast Kluyveromyces marxianus CDBB-L-278. It was found that 3.3 mg of DO/1 was the threshold for the repression of enzyme production. Growth temperature had no effect on the synthesis of this enzyme, but had an indirect effect due to changes in oxygen solubility. Growth rate was influenced by temperature; maintaining the dissolved oxygen constant at 3.3 mg of DO/1, the optimum growth temperature was 40 degrees C. Pectin in the culture medium allowed higher endo-polygalacturonase production; even with 3.3 mg of DO/1, pectin de-repressed the enzyme production.