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. pyrenoidosa, grown under low light and high carbon dioxide, is transferred suddenly to high light and low carbon dioxide. No other combina tion 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-dioxide 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.