STUDIES ON THE PROTEOLYTIC BACTERIA OF MILK III. ACTION OF PROTEOLYTIC BACTERIA OF MILK ON CASEIN AND GELATIN

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Abstract
The action of 229 cultures of proteolytic bacteria from milk on casein and gelatin was studied. Four species each of cocci and rods caused no increase in amino-N in casein or gelatin media. The remaining organisms fell into either high or low amino-N groups in casein and gelatin solutions. The bromine test was found to be positive in all cases of caseolysis except with Micrococcus cereus. M. varians broke down calcium caseinate but was apparently unable to split sodium caseinate. Some of the other organisms seemed to split calcium caseinate more readily than sodium caseinate. Increasing amounts of fermentable sugar up to 0.1 % did not affect appreciably the amount of caseolysis by most organisms. With M. percitreus, however, caseolysis decreased with increasing quantities of glucose. Caseolysis by the acid-forming Streptococcus liquefaciens was aided by more fermentable sugar. A study of the proteolytic milk organisms on casein and gelatin media is of value in the grouping of these organisms.