Design of a scalable, single-use photobioreactor for the growth of algae in axenic conditions
- Publication Type:
- Thesis
- Issue Date:
- 2021
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Microalgal cultivation systems for biopharmaceutical production are currently limited and current biopharmaceutical bioreactors are not optimized in terms of efficient light and substrate supply for algae. This project aims to address this gap, by establishing a process to convert and optimize a bioreactor system which is already established in the biopharmaceutical sector into a photo-bioreactor (PBR) system, facilitating axenic microalgae growth at an industrial scale in a regulated environment. The system to be converted is an industrially used single-use bioreactor, for which an optimization platform was designed including both physical and digital components. The physical part consisted of a 200 L PBR and a scaled down 20 L PBR, both mimicking physical characteristics of the industrial bioreactor, thereby enabling the rapid testing of new illumination systems. Different methods, such as gassing-in method (mass transfer), pH- and dye-method (mixing time) and optical particle tracing (hydrodynamic flow) were utilized to characterise the system and validate the down-scaling process, which revealed similar cultivation features compared to the industrial bioreactor. The predominant focus of the optimization platform was the supply of light: as such, accurate and precise data of the light attenuation were needed. A novel, practical, and easily applicable optical method using modified cameras for measuring the light distribution of complex light sources was developed to address this – Direct Chlorophyll Fluorescence Imaging (DCFI). DCFI was applied to 𝘗𝘩𝘢𝘦𝘰𝘥𝘢𝘤𝘵𝘺𝘭𝘶𝘮 𝘵𝘳𝘪𝘤𝘳𝘰𝘯𝘶𝘵𝘶𝘮 and 𝘊𝘩𝘭𝘰𝘳𝘦𝘭𝘭𝘢 𝘷𝘶𝘭𝘨𝘢𝘳𝘪𝘴 cultures at different cell concentrations for a variety of LED wavelengths, yielding precise light maps of the light distribution into the culture. These light maps and the particle tracing data were combined in a computer aided design (CAD) process which enabled the calculation of the best configuration of the artificial light system (LEDs) according to the optimal light experience for the microalgae cells. The CAD forms the digital component of the optimization platform and completes the system. The optimization platform and the underlying methodology builds the foundation for a streamlined approach to convert existing bioreactor systems or to optimize alternative PBR systems. As such, this technology can help in establishing microalgae as a cultivation system in the biopharmaceutical sector.
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