LARGE-SCALE CULTURE OF CHLORELLA 



PAUL M. COOK 

 Stanford Research Institute, Stanford, California 



Introduction 



Scientists recently have been studying the simplest photosyn- 

 thetic organisms, unicellular green algae, in their investigations 

 of the fundamentals of photosynthesis. Drs. H. A. Spoehr and 

 H. W. Milner of the Carnegie Institution of Washington's Divi- 

 sion of Plant Biology at Stanford University, began such a study 

 over eight years ago, using the common single-celled alga, Chlo- 

 rella pyrenoidosa Link. They have shown (1949) that the chem- 

 ical composition of the alga can be altered by changes in the envi- 

 ronmental conditions under which it is grown. They produced 

 Chlorella which had a protein content of over 50% by maintain- 

 ing a fixed nitrogen concentration above a critical value in their 

 culture medium. When the alga was grown in media containing 

 less than the critical value of .001 mol fixed nitrogen-content, 

 reproduction soon stopped and lipid was synthesized up to as 

 high as 85% of the dry weight. In this work considerable quan- 

 tities of Chlorella were grown and it was apparent that the rate 

 of growth was rapid. The possibility of the large-scale growth of 

 Chlorella was seen, and some calculations were made to deter- 

 mine what quantities of substances could be produced were the 

 plants cultured on a given area of land. 



The Research Corporation of New York was familiar with 

 the work of Spoehr and Milner and believed a survey should be 

 made to investigate the feasibility of making practical applica- 

 tions of the findings of Chlorella studies within the next few 

 decades. The Stanford Research Institute was engaged to make 

 the survey. The assignment was to analyze existing knowledge 

 derived from laboratory studies of Chlorella, to consider the 

 methods and problems involved in developing a large-scale proc- 



53 



