Abstract: Osmotic K.lactis cells were packed into packed bed reactor to hydrolyze lactose in milk.The thermal inactivation of lactase entrapped in K.lactis cells followed the first-order kinetics,and its half-life was 9.5h at 40℃.Appearent K_m constant and maximum reaction rate for the enzyme were 0.39 mmol/ml and 0.188 mmol/min,respectively.The optimal reaction parameters for hydrolysis of lactose in milk with osmotic K.lactis cells packed in 2.6 cm×50 cm column are:flow rate 1.0 ml/min at 40℃.Under these conditions,hydrolyzed glucose concentration reaches 45.2 mg/ml.

Key words: packed-bed reactor, osmotic K.lactis cell, lactase, lactose, continuous hydrolysis