42 THE ROLE OF ALGAE AND PLANKTON IN MEDICINE 



A great variety of apparatus has been employed to achieve the me- 

 chanical requisites. In 1951, Jorgensen and Convit in Venezuela grew 

 freshwater algae in unglazed baked red clay bowls exposed to the open air 

 and hot sun. The nutriment consisted of a commercial fertilizer suspended 

 in water. Evaporation from the porous sides of the bowls kept the tem- 

 perature at 26° C. even in direct tropical sunlight. Von Witsch and Harder 

 in Germany utilized nutrient solutions in glass tubes 3 x 30 cm. and 6 x 

 150 cm.; these were illuminated by 300-watt water-cooled lamps and 

 supplemented with an air stream containing 0.5 per cent carbon dioxide. 

 At the Carnegie Institution in Washington, greenhouse culture of Chlorella 

 was carried on in five-gallon bottles in 1947; illumination, temperature, 

 and carbon dioxide supply were controlled. This study led the following 

 year to activation of a successful pilot plant for continuous Chlorella 

 culture at the Stanford Research Institute. 



In 1949, Geoghegan in England tried out a variety of culture vessels: 

 cylinders 15 x 1.75 inches; large tubes 4.5 feet x 2.75 inches; aspirator 

 bottles 18 x 10.5 inches; and a tall outdoor plastic tank 4.5 feet high, 1.5 

 feet long, and 0.33 feet wide. He concluded that shallow horizontal 

 tubes or troughs were preferable, and that sunlight is more economical 

 than artificial illumination. Wassink and a group at the Agricultural 

 University at Wageningen in Holland experimented with mass Chlorella 

 culture from 1948 to 1950. Initially they used inverted half-liter glass- 

 stoppered bottles with incandescent light. Later they tried outdoor sunlit 

 square meter tanks with 300 liter capacity. The tanks were covered with 

 glass to minimize contamination; carbon dioxide was supplied from a 

 cylinder; and agitation was accomplished by a motorized stirrer. Algae 

 were harvested after 5 to 7 days of growth. Subsequently they set up 

 similar concrete tanks in a dark room and illuminated them with either 

 daylight fluorescent bulbs or high-wattage incandescent lamps. They ob- 

 tained a 12-20 per cent efficiency of light-energy conversion, and there- 

 from concluded that excessive illumination could decrease algal growth 

 under either artificial or natural conditions. 



Gummert and his colleagues, working in Essen in 1950-51, hoped to 

 demonstrate that local conditions were suitable for large-scale outdoor and 

 greenhouse culture that could take advantage of the huge amounts of 

 waste carbon dioxide in the industrial Ruhr. They succeeded for the most 

 part, but their deliberately nonsterile procedures resulted in troublesome 

 contamination with foreign algae and protozoa. This could be overcome 

 by using protozoa-resistant Scenedesmus, by altering the nutrient media, 



