LARGE-SCALE CHLORELLA CULTURE 75 



rates versus light intensities at high Hght intensities, and the deter- 

 mination of the growth mechanism when the cell is light-satu- 

 rated. Additional information on obtaining better growth rates at 

 high population densities and on the effects of contamination are 

 certainly needed. A clearer picture of the inhibition of growth by 

 metabolic products would be an important contribution. There 

 is no reason to believe that a better organism than Chlorella might 

 not be found. 



The general field is certainly an exciting and promising one; 

 one that in the next few years will show important advances. 

 Slowly it is being realized that photosynthesis has a potential of 

 great import when harnessed and properly utilized. The amount 

 of money spent on research in this field has been small but 

 already the results show great possibilities. 



Summary 



As the world becomes more and more dependent on energy 

 received from the Sun to synthesize its life-giving products, ways 

 must be devised to obtain greater efficiency in utilizing this 

 energy. Agriculture, even under the most favorable conditions, 

 converts but 3/ioths of 1% of a year's solar radiation to organic 

 matter, one half of which is essentially waste material (Daniels 

 1949). One promising method for producing large quantities of 

 protein, lipid, and carbohydrate has been presented in this paper. 

 On a small scale, as we have seen, 5% of the incident sunlight, or 

 over 2^^% of the total solar radiation, has been converted to or- 

 ganic matter. Excellent possibilities exist for improvements from 

 both short term and long range studies. 



The system we have described may not be the best nor the 

 organism used the most efficient. Only future studies can deter- 

 mine these matters. The important fact is that photosynthesis 

 has been used and controlled in a simple process. It can be har- 

 nessed by Man to produce needed products. We can look forward 

 to nev/ and better ways of putting photosynthesis — and the bound- 

 less source of energy provided by the Sun — to work for us. 



