Effect of oxygen on the growth (yield) of Chlorella vulgaris

Abstract

The growth yield of Chlorella vulgaris, Y kJ defined as g cells harvested per kJ of light energy absorbed by the cells, was assessed in a turbidostat culture by varying CO2 and O2 partial pressures ( $$p_{{\text{CO}}_{\text{2}} }$$ and $$p_{{\text{O}}_{\text{2}} }$$ ). The value of Y kJ ranged from 3.1×10-3 to 5.0×10-3 g cells/kJ under light-limited conditions [ $$p_{{\text{CO}}_{\text{2}} }$$ = 1.0∼2.4%, $$p_{{\text{O}}_{\text{2}} }$$ = 0∼65%; total pressure of gas (composed of CO2, O2 and N2)=1 atm]. In the light-limited environment, the algal specific growth rate μ deteriorated appreciably with the increase of $$p_{{\text{O}}_{\text{2}} }$$ . The deterioration accounts for the above range of Y kJ observed. The growth inhibition due to oxygen that was defined by subtracting from 1.0 the ratio of μ at given values of $$p_{{\text{O}}_{\text{2}} }$$ to that at $$p_{{\text{O}}_{\text{2}} }$$ = 0% extended from 0.07–0.30 (7–30%). However, glycolate could not be detected in the turbidostat culture. Isotopic experiments on the specific rate of 14CO2 uptake also revealed that the inhibition due to oxygen was from 22–38% when $$p_{{\text{O}}_{\text{2}} }$$ was varied from 0 to nearly 100%. These effects of oxygen were discussed, referring to the activity of ribulose-1,5-bisphosphate carboxylase that is inhibited competitively by oxygen.