Relationship between substrate inhibition and maintenance energy of Chlamydomonas reinhardtii in heterotrophic culture

The relationship between substrate inhibition and maintenance energy of Chlamydomonas reinhardtii grown heterotrophically on acetate was investigated. At low acetate concentrations (<0.4 g l(-1)), where no inhibition of cell growth was observed, the cell growth yield and specific growth rate could be represented by the Pirt model, 1/Y = 1/Y-g + m/mu with a constant value of maintenance energy coefficient m. However, at high acetate concentrations (>0.4 g l(-1)), inhibition of cell growth occurred, in which m became variable and dependent on the acetate concentration. A simple mathematical model was proposed to predict the actual maintenance energy coefficient m in the inhibited cultures and experimentally validated.