The beta-galactosidase from Kluyveromyces lactis is a high molecular weight protein with commercial interest. A major drawback of its industrial production is the high cost associated with extraction and downstream processing due to its intracellular nature. In this work, the effectiveness of the utilization of Saccharomyces cerevisiae LD1 and LHDP1 strains, osmotic-remedial mutants which lyse at 37 degrees C, for the heterologous production and release into the extracellular medium of this protein has been proved. The highest absolute values of released beta-galactosidase have been obtained with the protease-deficient strain LHDP1 by osmotic shock.