LARGE-SCALE CHLORELLA CULTURE 63' 



The symbols as used are defined as follows: 



K-D — growth rate (for i day) 



Vq — volume of overflow in liters 



Vc — volume of culture in liters 



/\tD — time in days (24 hours) 



Yd — yield (grams dry weight per liter per day) 



Dc — population density (grams dry weight per liter) 



Growth rate of high-protein Chlorella when maintained 

 under constant culture conditions is a function of the population 

 density and light intensity. Under the constant light conditions 

 of the 4-inch artificial Hght column, we have made many experi- 

 ments at different population densities. The results of one such 

 experiment are shown in Figure 6 where volume of overflow is 

 plotted versus time. The volume of overflow is constant with 

 time and the slope of the line is the growth rate on an hourly 

 basis. In several experiments particularly at high population den- 

 sities a considerable period of time was required to reach equi- 

 librium conditions and to obtain a constant increase in overflow 

 volume per unit time. 



Figure 7 shows the growth rate versus population density for 

 several experiments conducted in the artificial light 4-inch col- 

 umn (as above) with optimum culture conditions. Yield, the 

 product of growth rate and population density in grams dry 

 weight per liter, is plotted versus population density in Figure 8. 

 This curve shows a maximum yield at a density of 0.36 grams 

 dry weight per liter. The maximum production obtained from 

 such a system is 0.48 grams dry weight per liter each day. 



Similar information has been obtained with the sunlight 4-inch 

 column. The results of one experiment are shown in Figure 9 

 where overflow volume is plotted versus time and date. The daily 

 weather conditions and overflow volume are indicated. This ex- 

 periment was carried out at a population density of 0.27 grams 

 per liter with the column perpendicular to the earth. The daily 

 average yield for this experiment was 0.279 grams per liter and 



