Production of Beta-D-Galactosidase from Kluyveromyces fragilis Grown in Cheese Whey

Two strains of Kluyveromyces fragilis (145 and 276) and one of Kluyveromyces lactis were tested for their abilities to produce beta-D-galactosidase in cheese whey. Kluyveromyces fragilis 145 was selected for its higher beta-D-galactosidase activity per cell at the end of the exponential growth phase.Addition of ammonium sulfate (.3%) and yeast extract (.1%) to the deproteinized cheese whey increased cell mass and enzyme yield.Addition of 3% lactose did not affect beta-D-galactosidase activity per cell, which responded positively to a reduction in aeration from 1 to .25 air volume/medium volume/min.The harvested yeast cells were ethanol- and acetone-permeabilized to enhance lactose hydrolysis by beta-D-galactosidase.