It is demonstrated by experiments and calculations that the medium used for growing the microalga Spirulina (prepared according to ZARROUK¹ with a resulting pH of 8.7) is highly meta-stable in contact with the atmosphere and is thus loosing considerable amounts of CO2. This economic problem can be avoided by raising the pH of the culture medium to 10.2 where its partial pressure of CO2 corresponds to the partial pressure of CO2 in the atmosphere. The pH shift has practically no influence on the growth of the algae.
Spirulina; CO2; sodium bicarbonate
