The constant volume of the reactor was maintained by feeding (inflow) the diluted un-pasteurized cheese whey (un-pasteurized cheese whey was used to evaluate the contaminants during the continuous process) supplemented with 0.15% w/v of urea at a predetermined flow rate with a peristaltic pump and pumping out (outflow) the fermented broth at equal flow rate with another peristaltic pump (Masterflex, Cole-Palmer, USA).