Experimental and model-based parameterization of the fundamental process kinetics of Chromochloris zofingiensis

Abstract

The microalgae Chromochloris zofingiensis has attracted considerable interest due to its remarkable ability to accumulate high value metabolites. Current research focuses primarily on laboratory-scale cultivation, while the development of fundamental model frameworks for process upscaling is neglected. In order to develop an effective scale-up process for C. zofingiensis, it is crucial to identify the strain-specific kinetics and dependencies on the environmental factors affecting its growth (light, temperature, pH, nutrients and dissolved oxygen concentration), as many of them remain unknown. This study represents a combination of different experimental and model-based approaches to parametrize the key growth parameters of C. zofingiensis, as well as its response kinetics towards different cultivation factors for model framework construction and calibration. The optimal temperature, DOC and PAR intensity for photosynthesis were successfully determined to be 26.58 °C, 6–7 mg_O₂/L, and 22.42 μmol/(m² s), respectively. This enabled the development of a model-based control strategy, by maintaining the average PAR intensity within the PBR at its optimal range of 20–30 μmol/(m² s), to ensure an efficient scale-up process, which effectively improved the productivity by a factor of 5 when scaling up the cultivation of C. zofingiensis to a 200 L pilot-scale PBR.