Modelling of Biomass Concentration, Multi-Wavelength Absorption and Discrimination Method for Seven Important Marine Microalgae Species

Due to the possible depletion of fossil fuels in the near future and the necessity of finding new food sources for a growing world population, marine microalgae constitutes a very promising alternative resource, which can also contribute to carbon dioxide fixation. Thus, seven species (Chaetoceros calcitrans, Chaetoceros gracilis, Isochrysis galbana, Nannochloropsis gaditana, Dunaliella salina, Tetraselmis suecica, and Tetraselmis chuii) were grown in five serial batch cultures at a bench scale under continuous illumination. The batch cultures were inoculated with an aliquot that was extracted from a larger-scale culture in order to obtain growth data valid for the entire growth cycle with guaranteed reproducibility. Thus, measurements of optical density at several wavelengths and cell counting with a haemocytometer (Neubauer chamber) were performed every one or two days for 22 days in the five batch cultures of each specie. Modeling of cell growth, the relationship between optical density (OD) and cell concentration and the effect of wavelength on OD was performed. The results of this study showed the highest and lowest growth rate for N. gaditana and T. suecica, respectively. Furthermore, a simple and accurate discrimination method by performing direct single OD measurements of microalgae culture aliquots was developed and is already available for free on internet.