Gas Exchange of Algae

A single culture ofChlorella pyrenoidosa (700 ml) was grown continuously under uniform environmental conditions for a period of 11 months. During this time, the culture remained uncontaminated and its oxygen production, carbon dioxide consumption, and photosynthetic quotient (PQ = CO2 /O2 ) were monitored on a 24-hr basis. The gas exchange characteristics of the alga were found to be extremely reliable; the average oxygen production was 1.21 ± 0.03 ml per min, the carbon dioxide consumption was 1.09 ± 0.03 ml per min, and the PQ was 0.90 ± 0.01 when changes in both lamp intensity and instrument accuracy were taken into consideration. Such long-term dependability in the production of oxygen, consumption of carbon dioxide, and maintenance of a uniform PQ warrants the use ofC. pyrenoidosa in a regenerative life support system for space travel.