We have developed and characterized a new low-cost enzymatic preparation for milk whey saccharification. The preparation consists of beta-galactosidase-rich whole cells of the yeast Kluyveromyces lactis,previously cultured on milk whey and immobilized by covalent linkage to corn grits (an inexpensive material). Permeabilization of immobilized cells with ethanol increased the measured values of intracellular beta-galactosidase activity up to 240-fold. Permeabilized immobilized cells hydrolyzed milk whey lactose mole rapidly than untreated cells, and did not further metabolize the glucose and galactose produced. More than 90% milk whey lactose hydrolysis was achieved in a packed-bed bioreactor at 37 degrees C.