The Fermentation of Glycerol by Streptococci

Abstract

Oxygen is necessary for acid production from glycerol by the majority of lactic acid bacteria. These organisms, which lack iron catalysts, require O2 to utilize glycerol as an energy source. Of the organisms tested only some "enterococci" and 1 strain of Lactobacillus produced acid from glycerol anaerobically. Whether acid is produced aerobically or anaerobically the limiting pH is about 5. When acid production under aerobic conditions is used as a criterion of fermentation, suggestive results are obtained: the Group C streptococcus of the so-called "human" variety ferments glycerol; the "animal"'' var. does not. In Group G the "minute" type does not ferment glycerol whereas the other members of the group do. All members of Groups B and D tested ferment glycerol. None of the members of Group A tested nor members of the "lactic" and "viridans" groups of streptococci produced acid from glycerol under the conditions used.