Abstract Whole cells of bakers’ yeast ( Saccharomyces cerevisiae) exhibited very low catalase activity (16 U g −1). Various treatments altered membrane permeability and increased cellular catalase activity. Treatment with cetyltrimethylammonium bromide (CTAB) yielded maximum catalase activity (51000 U g −1) followed by digitonin (27072 U g −1). After permeabilization of the membrane, the catalase slowly leaks out of the cells. The half-life of intracellular catalase in CTAB-permeabilized cells was 3.4 days at 4°C and 1.2 days at 26°C. Catalase in permeabilized cells was more stable against self-inactivation during catalysis than the enzyme in cell-free extract and purified catalase. Catalase of CTAB-permeabilized cells was effective in removing the residual H 2O 2 from H 2O 2-treated fresh milk/heat pasteurized milk.