62 P. M. COOK 



of determining the value of Chlorella as a source of foods or of 

 chemicals. Work to date has been limited. Preliminary nutrition 

 studies with rats have been made in which diets having all pro- 

 tein supplied by Chlorella were used. Feeding experiments with 

 a normal complete diet supplemented with Chlorella also have 

 been made. Some chemical biological analyses have been made 

 both by our own laboratories and by other organizations. 



Results 



Only a brief and general report of our results is possible here. 

 Only the important results as they pertain to the objective of pro- 

 ducing the maximum quantity of Chlorella most efficiently on a 

 large scale will be discussed. 



Growth rate refers to the amount of growth in a culture per 

 unit of time. In a batch culture growth rate is measured in terms 

 of increase in cell count per unit volume per unit time. The 

 growth rate in such a batch culture is not constant due to chang- 

 ing culture conditions and, therefore, is difficult to determine 

 accurately. In a continuous system where population density and 

 other variables are held constant, growth rate, expressed in liters 

 of overflow of culture per liter per day, is measured by the amount 

 of dilution (or the amount of overflow of culture obtained due to 

 the dilution) necessary to maintain constant population density 

 for a constant volume of culture. In a continuous system which 

 maintains constant culture conditions, the growth rate is directly 

 proportional to the rate of reproduction. 



Growth rate is defined as: 



Vo I 



K.n — 



Vc AtD 



The yield (grams per liter per day) is the product of the 

 growth rate (liters per liter per day) and the population density 

 (grams per liter), and it is expressed as grams of material grown 

 in a given period of time per liter of culture. It is also a direct 

 expression of production in the continuous process. Yield is 

 defined as: 



Yd = -^ -^ or Yd = KdDc 



Vc AtD 



