34 THE ROLE OF ALGAE AND PLANKTON IN MEDICINE 



extracts, for example, have been shown to contain transaminase systems 

 which aid the transfer of amino groups to either pyruvic or rf-keto-glutaric 

 acid. 212 The most active enzyme systems in algae are those of aspartic 

 and glutaric acids, and alanine. 



Spoehr and Milner 41 demonstrated that the composition of Chlorella 

 pyrenoidosa could be varied specifically simply by controlling cultural 

 conditions. In over 300 pure cultures, it has been possible to produce the 

 following wide range of variations in composition and R-value: 



Protein: 7.3 to 88.0% Carbohydrate: 5.7 to 38.0% 



Lipid: 4.5 to 86.0% R-value: 37.92 to 63.33 



The amount of radiant energy present markedly influences the rate of 

 growth of a culture, either directly or by increasing the nitrogen absorp- 

 tion. The latter is certainly of critical importance, since a Chlorella cell 

 can no longer undergo fission when the nitrogen content falls below 

 1.6 x 10- 13 gm. 



As has already been indicated, the protein content of microscopic algae 

 may vary widely; its level may be grossly estimated from the nitrogen 

 content. There is a definite similarity in the protein content of Chlorella 

 and the leaves of many higher plants. Under optimal cultural conditions, 

 a protein level can be achieved in Chlorella which exceeds that of the best 

 vegetable substances used as animal feed. This includes such materials as 

 Brewer's yeast, torula yeast, soybean meal, dried skimmed milk, and wheat. 



Not very much is known of the specific nature of algal proteins, except 

 that there is often a resemblance between their amino acid patterns and 

 those of higher plants. 213 " 215 The nutritional value of Chlorella is based 

 not merely on its high protein content, but also on the fact that it con- 

 tains all the essential amino acids. Methionine is present in only small 

 amounts, but this deficiency also occurs in many vegetable proteins. The 

 essential amino acid Biological Index of Chlorella vulgaris has been calcu- 

 lated to be 62 in a pilot plant assay, as compared with an arbitrary value 

 of 100 for whole egg protein. The Index of most animal proteins ranges 

 from 80 to 90, while cereal proteins are usually between 60 and 80. Thus 

 Chlorella is roughly comparable to white flour, corn gluten, and peanut 

 meal. An amino acid assay of dried Chlorella is given in Table IV. 



Although most algae are able to utilize wide varieties of basic inorganic 

 nutrients and to synthesize from them the more complex metabolites re- 

 quired, some are not so versatile. They may not be able to synthesize all 



