The Kinetics of Extracellular Glycollate Production byChlorella pyrenoidosa

Abstract

Extracellular glycollate is liberated by Chlorella pyrenoidosa during growth in medium bubbled with air or 3 per cent carbon dioxide in air. With air the rate of release of glycollate per cell decreases, with 3 per cent carbon dioxide it increases, with increase in cell number. Glycollate is released during short-term experiments when C. pyrenoidasa, grown under low light and high carbon dioxide, is transferred suddenly to high light and low carbon dioxide. No other combination of these factors produces a comparable release of glycollate. The quantity of glycollate released in short-term experiments increases exponentially with the relative growth-rate of the culture from which the cells are derived. A crucial condition for maximum glycollate release is that growth of the culture prior to the experiment should not be limited by carbon-dixoide concentration. The effect of pH is related to its effect on growth-rate; i.e. C. pyrenoidosa has a lower relative growth-rate at pH 8.3 and produces correspondingly less glycollate than faster growing cultures at pH 6.4. During short-term experiments under high light and low carbon dioxide the rate of glycollate release drops after 50–100 minutes suggesting exhaustion of the glycollate precursor.