Abstract: Disclosed is a method of growing a mixture of two or more species of lactic acid producing bacteria whose growth rates are differently affected by the pH of the nutrient growth medium. The method involves maintaining the pH of the medium at a low level which actively selects for the growth of one species until that species has reached the desired concentration. The pH is then raised to a level that actively selects for the growth of another species and maintained at this level until that species has reached the desired concentration. The method is especially useful for preparing a starter culture for Italian type cheese containing a mixture of coccus and rod bacteria because the ratio of these bacteria, one to the other, can be closely controlled.