Organic Nitrogen Preferences of Zoogloea ramigera

in enzymatic content of the cells. Throughout the course of this study, grading of the amount of growth by visual estimation has been a routine observation. Once a certain minimum amount of mycelium was present there did not seem to be an apparent correlation between the amount of growth and the yield of the desired steroids. In the experiments where dextrin replaced sucrose as the carbohydrate of the medium, it was difficult to make visual comparisons of growth in this modified medium with that in the standard Czapek-Dox solution because of the altered form of the mycelium. Moist weight determinations were likewise impracticable because of the presence of excess, insoluble dextrin in the solutions. When fatty acid esters, such as the monoglycerides, were used, similar problems in moist weight determinations were encountered. It is of interest to note in table 5, however, that the only easily apparent differences in the amounts of cells produced occurred when monoglycerides of either soybean oil or castor oil were present in the medium. Soybean oil monoglycerides were without effect in stimulating steroid oxidation and castor oil monoglycerides were, in contrast, the most effective. Thus, despite close chemical similarities of either complex carbohydrates or fatty acid esters, important differences exist in their effect on the microbiological reaction, regardless of the precise mechanism involved.