Abstract :
Many models of microalgal growth focus on steady state carbon budgets. This approach can be very useful if oneʹs primary purpose is to predict growth on the basis of a limited set of measurements. However, it is less likely to be successful if one purports to understand the regulation of growth in response to variations in, for instance, the nutrient concentrations in the environment. For such a purpose, models based on variable internal stores are more suited. In this paper, I present a variable internal stores model of microalgal growth, focusing on the kinetics of the limiting as well as the non-limiting nutrient. Data from chemostat steady states are well described by the model. The model provides an underpinning for the well established Droop equation for growth on a limiting nutrient. the model also shows that ther is no meaningful basis for the Droop equation for non-limiting nutrients. It is likely that the approach followed in this paper can also be applied to the kinetics of carbon. With respect to the model presented in this paper, the main difference between carbon and other nutrients is the photosynthetically driven uptake of CO2. Once taken up, the kinetics of carbon may be similar to that of other nutrients.
