Gas exchange of algae. IV. Reliability of Chlorella pyrenoidosa

A single culture of Chlorella 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 = CO(2)/O(2)) 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 of C. pyrenoidosa in a regenerative life support system for space travel.