Dynamic DOE to optimize the high value compounds in Coccomyxa onubensis in a novel high cell density cultivation system

Microalgae are photosynthetic microorganisms that have emerged as a sustainable alternative to produce high-value bioactive molecules. Microalgae-derived bioproducts are experiencing a significant increase in industrial applications, ranging from pharmaceuticals to bioenergy, owing to their high productivity of the compounds of interest and their low environmental impact compared to synthetic alternatives. However, stringent European regulatory restrictions pose challenges to microalgae production for human applications. These challenges limit such endeavors to closed photobioreactors characterized by high levels of automation and significant sterilization costs. A challenge for the future is to enhance and optimize the growth of microalgae to increase productivity while limiting contamination from other microorganisms such as bacteria. In this study, the acidophilic microalgae Coccomyxa onubensis capitalizes on its ability to thrive in acidic conditions, yielding high amounts of carotenoids, especially lutein, and preventing bacterial contamination. The study applied a dynamic design of experiments (DDoE) to Coccomyxa onubensis to optimize the production of biomass and high-value compounds. Cultivation was conducted in a batch system with automated control and monitoring of environmental variables. The microalgae were grown in a high-density cell system equipped with a hydrophobic membrane, optimizing photoautotrophic growth through CO2 provision by diffusion. This allowed for the establishment of different profiles of light intensity and CO2 partial pressure. By employing DDoE, meticulous control over key variables, including dynamic light intensity profiles ranging from 80 to 800 μmol/m2/s, the feeding strategy of nitrogen between 60 and 600 mg/L, and constant partial pressure of CO2, systematically optimized growth conditions. The study explores three-tiered CO2 partial pressure, with the highest concentration reaching 10%, establishing a correlation with the mitigation of CO2 emissions from significant industrial sectors, including power plants.