About Microalgae Growth Kinetics Modeling

Microalgae are a natural source of high-value compounds for the pharmaceutical and food industry, such as bioactive compounds, vitamins, pigments and fatty acids.1 In addition, in the long term, algae culture may be useful for production of clean fuels. Photosynthetic algal culture is carried out in photobioreactors that may be illuminated naturally (outdoor) or artificially (indoor). Availability and intensity of light are the major factors controlling productivity of photosynthetic cultures.2 Photobioreactors using algae, plants cells or photosynthetic bacteria have received considerable attention from biochemical engineers. Industry is presently engaged in developing new products and testing a new generation of algae-derived natural products.3 The algae near the irradiation source are exposed to high photon flux density, which enhances their growth rate. The cells at the core of the reactor receive less light as a result of mutual shading and will show a lower growth rate.4–7 The process of photosynthesis can be distinguished into light and carbon-fixation reactions because they are physically separated.8,9 Photosynthesis is obviously linked to the availability of carbon dioxide. Although several cell-based models of photosynthesis have been proposed,10–19 they consider only the light availability. These models both use classic enzyme kinetics and assume slow enzyme-controlled reactions dependent only on light to account for the carbon-fixation reactions10,13,16,19 or assume that photosynthetic rates are mainly related to light intensity.14,16,18 Other models recognize the CO2 dependence but ignore it in the model15 or assume that carbon fixation is proportional to the light intensity and the available carbon.20