Chemometric Modeling of Microalgal Nutrient Sequestration as a Function of Their Chemical Environment

Abstract

ABSTRACTMarine microalgae sequester large quantities of inorganic compounds by way of photosynthesis. Therefore, phytoplankton has a considerable environmental impact as it contributes to counter-balancing anthropogenic releases of CO2. However, open questions remain regarding interactions between microalgae and their environment in particular the inorganic compounds which cells consume as nutrients. On the other hand, Michaelis–Menten (MM) kinetics links environmental chemistry and microbiology as it concurrently explains the cells’ uptake of nutrients and utilization for cell production. Thereby, cells modify the chemical composition of their growing environment, which in turn is hypothesized to impact the cells’ sequestration capabilities. However, the system of ordinary differential equations (ODEs) that represents MM cannot be solved without further considerations, as it contains unknown physiological parameters. These parameters though are of central interest, as they describe the cells’ compound uptake in a certain chemical environment. Innovations in chemometrics are presented that derive values for these parameters as a function of the cells’ nutrient availability. For this purpose, the MM ODE system has been merged into nonlinear least-square regression in lieu of a fit function. By this approach, it is demonstrated that microalgae’s nutrient uptake is indeed driven by chemical conditions in their growing environment. These results are also indicative that the chemical conditions in a microscopic vicinity of the cells are relevant rather than nutrient concentrations on a culture level. These proof-of-principle results underline that for an accurate assessment of such chemically active samples, it is necessary to consider both the cells and their chemical environment.