FIG. 3.

Effect of aeration on the growth of L. delbrueckii subsp. bulgaricus (A) and the concentration of hydrogen peroxide concentration in the culture medium (B). Open circles, unaerated still cultures; closed circles, aerated cultures. The arrow shows the time at which aeration was started. MRS medium without beef extract and with 2% lactose was used. Growth was measured through changes at A₆₀₀. The hydrogen peroxide concentration of the supernatant was determined after rapidly centrifuging the cells.