A Soluble Protein Extract from Soy Beans. 219 



citrated, salted, hirudinized, filtered plasma, etc.). 1 We have 

 now observed that sterile filtrates of the above mentioned dis- 

 solved cultures of staphylococci possess the same property. 



no (1692) 



On the preparation of a soluble protein extract from soy beans. 



By SELMAN A. WAKSMAN. 



[From the New Jersey Agricultural Experiment Station, 

 New Brunswick, N. J.] 



The average protein content of the soy bean is 36.5 per cent, 

 while that of the soy bean cake is about 41 per cent. The protein 

 of the soy bean has all the amino acids necessary for nutrition and 

 it is claimed to be as valuable as the casein of milk. The proteins 

 of the soy bean, unlike those of other leguminous plants thus far 

 investigated, were found, by Osborne and Mendel, to be adequate 

 for promoting normal growth. In addition to the high protein 

 content, the soy bean is found to contain an adequate amount of 

 water-soluble vitamine and some essential fat-soluble vitamine. 

 These factors combined with low cost make the soy bean of unique 

 significance as a food. 



In working with proteolytic enzymes of fungi, the author found 

 some organisms that are able to develop active enzymes which 

 readily hydrolize the soy bean proteins and make them soluble. 

 By using the ground soy bean cake as a substratum for the growth 

 of the proteolytic fungus, then, at the end of the proper incubation 

 period, which is usually about 36 hours, adding water to the mass 

 and allowing the enzyme present in the mycelium to act upon the 

 soy bean proteins, over 50 per cent of the proteins are found to 

 go into solution. This solution when concentrated gives a material 

 containing 45 or more per cent of soluble proteins and protein 

 degradation products and is quite rich in vitamines. This extract 

 can be very cheaply prepared and it may take the place, when 

 properly modified by the addition of necessary salts, of meat 

 extract and other digested meats in infant feeding and, since the 



1 Compt. rend. Soc. Biol., 1919, lxxxii, 1245, 1247, 1393; 1920, Ixxxiii, 649, 584, 

 58S. 649. 



