Growth of Chlorella in a Nitrate-limited Chemostat

Abstract

Chlorella pyrenoidosa was grown in a continuous-flow chemostat under nitrogen-limited conditions. The population density tended to oscillate very significantly. Net specific growth rate was only approximately a hyperbolic function of nitrate concentration in the chemostat. The best estimate of the half-saturation constant for nitrate is 6 mug of nitrogen per liter and it is unlikely that the value is greater than 14 mug per liter or 1 mum nitrate.The dry weight production of cells per unit of nitrogen taken up is a linearly decreasing function of the net specific growth rate with a maximum of 27.1 mg per mg N and a minimum of about 9 mg per mg N. Thus there is considerable storage of nitrogen at high growth rates. Both the dark respiration rate and the rate of photosynthesis at light saturation increase with increasing net specific growth rate.