acids are biologically active, that is, they are metabolized in the animal 

 organism, while the synthetic amino acids ^.re only 50 percent active due 

 to the fact that they are made up of an equal mixture of the active and 

 the inactive forms. This means that double the amount of synthetic amino 

 acid is required to give the same biological response as the natural form 

 of the amino acid. In addition, it hss been reported by Albanese and Irby 

 (1) that the introduction of the inactive form into the nutrition of the 

 animal has an inhibitinj3 or damaging effect. 



The amino acids are clissified further into what are termed "essential" 

 or "indispensable" and "non-essential" or "dispensable" amino acids. The 

 "essential" or "indispensable" amino acids have been determined by experimental 

 animal feeding tests and have the special significance that when any one 

 of the 10 indispensable acids are absent from the diet, growth of the 

 animal ceases. 



Uses 



Amino acids and their salts are used in a number of different ways. 

 Certain individual amino acids and mixtures of then are used in medicine, 

 in the treatment of ulcer and bum cases, in the treatment of shock, and 

 after major abdominal surgery. Tryptophane and methionine are used to 

 fortify protein hydrolysates in order to enhance their nutritional value. 

 The amino acid, lysine, is being promoted for the supplementation of various 

 vegetable protein feeds which are deficient in this essential amino acid. 

 Sodium glutamate is being widely used to add a meat flavor to soup mixes, 

 sauces, and food concentrates. Experimental investigations designed to 

 determine special functions of certain amino acids such as arginine in the 

 treatment of some pathological conditions may lead to an enlarged use of 

 amino acids. 



Present sources of raw material 



Both natural and synthetic amino acids are at present being used com- 

 mercially and in medicine. The natural occurring amino acids are being 

 prepared from tuna and mackerel fish residues, ^^luten of wheat, soybean pro- 

 tein, "oteffens waste" liquor, and other animal and vegetable materials. 



The synthetic amino acids are produced chemically from simpler organic 

 compx)unds such as hydrocarbons and cyanide. 



Methods and economics of manufacture 



The production of natural amino acids from various animal and vegetable 

 sources can be accomplished by preparation of a hydrolysate of the protein 

 followed by isolation of the amino acid by means of heavy metal precipi- 

 tation and fractional crystallization. The isolation process is expensive 

 and time-consuming, so that the cost of the natural amino acid is usually 

 higher than the corresponding synthetic form, when both are available. How- 

 ever, since the natural form is twice as active as the synthetic, the 

 natural is more desirable for some purposes. There are some amino acids 



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