Effect of medium on growth and subsequent survival,after freeze-drying,ofLactobacillus delbrueckii subsp.bulgaricus

Summary Growth ofLactobacillus delbrueckii subsp.bulgaricus, grown at a constant pH (5.7) in papain-or pepsin-treated whey was superior to that in whey or whey permeate, but inferior to growth in milk; it was not significantly different from that found in a 1:1 whey: milk medium. When 2% sodium citrate was added to the fermented medium, the cell recovery levels (59–75%) upon centrifugation were not significantly different in papain-treated media compared to untreated substrates. Cultures obtained from papain-treated milk or whey showed similar mortality levels following freeze-drying (99%) to those grown on untreated milk or whey. Addition of Tween 80 to the growth medium improved survival rate by a factor of ten.