Abstract
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.
Highlights
Commercial production of the “magic” blue-green microalga Spirulina, a desired health food, is steadily increasing around the world
Most producers use in the growth medium a salt composition as given by Zarrouk[1] with sodium bicarbonate as carbon source which counts for at least 60% of all nutrient costs
To simplify the complex ionic situation as it exists in the real medium, we considered for the calculations a pure bicarbonate solution, i.e. neglecting ionic interactions with other species present in the medium
Summary
Commercial production of the “magic” blue-green microalga Spirulina , a desired health food, is steadily increasing around the world. Though very effective for high algae productivity, requires special attention, in order not to flush out fast CO2 from the medium. A Spirulina medium prepared according to the recipe of ZARROUK (with 16.8 g/L of bicabonate) has a pH of 8.7; practically the same pH results, if the bicarbonate amount is reduced to one half.
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