Steady state growth kinetics of Chlorella vulgaris under double substrate (urea and phosphate) limitation

Change from phosphate‐limited growth to nitrogen‐limited growth at a fixed specific growth rate (μ) was investigated. To account for the specific growth rate control by the two substrates there was little to choose between a relation involving both substrate concentrations and one which involved only the substrate concentration which, by itself, gave the minimum value to μ. Double substrate limitation of growth was manifested by variations in the nitrogen and phosphorus contents of the biomass over a considerable range of urea and phosphate concentrations in the culture medium at a given growth rate. These changes in the elementary composition of the biomass were accounted for by the theoretical model of Panikov and Pirt.