METHOD FOR PRODUCING SINGLE AND/OR MIXED STRAIN CONCENTRATES OF BACTERIA

摘要

An improved method which differentiates or separates heterogeneous populations of fast and slow acid producing strains of bacteria by growth of the strains under closely controlled unique conditions so as to allow the selection of a colony of one or the other strains is described Preferably a gelled, solid growth medium containing in admixture: (1) milk protein, a milk protein derivative or a milk protein substitute; (2) an acid pH sensitive color change indicator; and (3) a buffering agent is used. The colonies have a contrasting color within and around them because of the effect of the acid produced by the bacteria on the indicator. The growth of the bacteria is under anaerobic or near anaerobic conditions in order to achieve certainty in the colony selection for fast or slow acid production. The bacteria can also be mixed with phage which inhibit or kill the members of a heterogeneous or homogeneous population of bacteria on the medium and grown to produce phage resistant colonies. The relatively large colonies which exhibit enhanced acid production and proteolysis of the milk protein on the plating container are selected for commercial use in preparing fermented products, particularly fermented foods.