A bioreactor comprising of three concentric cylinders of different diameter for demarcating the liquid flow and enzyme cartridge, said cylinders comprising an outer water circulation cylinder (2) to maintain the reactor temperature from 5° - 95°C, a middle concentric cylinder (1) to hold the lactose hydrolyzed milk/product and is connected to a water delivery tank (14) and an innermost cylinder (4) is enzyme cartridge to hold the immobilized lactase in the form of a packed bed.
