LOUIS FREEDMAN 23 



TABLE II. (b) (continued) 



PH after 

 No. Hydrolysates of Vegetable Proteins. Growth incubation 



23. Legumelin 7.3 



23 (a). (sterile control) 7.3 



24. Oryzenin 7.0 



24 (a). (sterile control) 7.2 



25. Hordein 7.0 



25 (a). (sterile control) 7.3 



26. Yeast protein -f 4.9 



26 (a). " (sterile control) 7.3 



These quantitative results confirm our first results, namely, 

 that only two of our animal and two of our vegetable proteins 

 contain the growth stimulating vitamine for streptococci in 

 appreciable amounts. Of the proteins whose hydrolysates con- 

 tain the active substances, yeast protein is by far the richest, 

 with casein second, commercial gelatin closely following, and 

 edestin containing the smallest amount of the active substance. 



EFFECT OF PROTEIN HYDROLYSATES ON GROWTH OF YEAST. 



The protein hydrolysates as described above were tested on 

 yeast; and, with the exception of casein and yeast protein, all 

 the hydrolysates either failed to stimulate, or actually inhibi- 

 ted, the growth of yeast cells. Even the action of casein and 

 yeast protein hydrolysates were, however, practically negative, 

 the net increase in growth of yeast cells due to the vitamine 

 activity of the hydrolysates amounting to one mm. for each 

 of these proteins. 



These results are not at all surprising, as Vansteenberge 12 

 found that leucine, tyrosine and asparagine inhibited the 

 growth of yeast cells but not of the lactic bacteria. All of our 

 hydrolysed proteins contain large amounts of leucine, while most 

 of them contain varying amounts of tyrosine and aspartic acid. 



A close analysis of the results obtained with these proteins 

 together with their method of purification and their physical 

 structure will, if anything, tend to confirm our view that the 

 growth-stimulating action is due, not to any constituent part 

 of the protein molecule, but to the tendency of the protein to 

 adsorb vitamine and hold on to it in spite of all attempts at 

 purification. Thus, yeast protein, the hydrolysate of which gave 

 considerable stimulation to the growth of streptococci, was ob- 



