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[Display omitted] • A modelling visualised flow field changes in a photobioreactor was established. • Utilised 24 baffles to enhance hydrodynamic effects on an increase in cell numbers. • Achieved high growth rates for C.vulgaris in PBRM at airflow rates of 45−50L/h. • Observed composition variations in cells with CO 2 concentrations ranging from 5−20% • Introduced newly proposed PBRM featuring ordered vortex pairs that benefit cultures. Microalgae play a crucial role as bioresources, yet the culture systems of photobioreactors (PBR) encounter challenges. Many engineered PBRs tend to incorporate internals build-ups, serving photoautotroph production, and requiring substantial microalgal biomass. This study quantified the baffle effects on airlift flat plate PBRs based on the performance of Chlorella vulgaris. The impacts of baffle configurations, air velocity, and CO 2 contents, three dominant parameters, on microalgae culture were investigated using culture experiments, numerical simulations, and flow visualisation techniques. The results demonstrate that multiple baffle design strategies enhance microalgae growth and production. On the 11th cultivation day, airflow rates of 6, 45, or 90 L/h produced 1.5, 3.0, or 1.9 times the biomass weight and 1.76 × 107 cell numbers/mL in PBR M with 24 baffles, compared to 1.44 × 107 cell numbers/mL in PBR C without baffles. Furthermore, it revealed an intensification in the generation potential of biocomponents with C–H, C = O, and C–O–C functional groups at a 45−50 L/h airflow rate and CO 2 (20 %) aerated PBR M. Additionally, it presented the first visualisation explanation of the baffle-guided vortex flow pair symmetry PBR M. This study demonstrated enhancements by modelling newly proposed PBRs with baffles and high-valued bioproducts harvesting through the combination of culture parameters. [ABSTRACT FROM AUTHOR]

Microalgae are photosynthetic microorganisms playing a pivotal role in primary production in aquatic ecosystems, sustaining the entry of carbon in the biosphere. Microalgae have also been recognized as sustainable source of biomass to complement crops. For this objective they are cultivated in photobioreactors or ponds at high cell density to maximize biomass productivity and lower the cost of downstream processes. Photosynthesis depends on light availability, that is often not constant over time. In nature, sunlight fluctuates over diurnal cycles and weather conditions. In high-density microalgae cultures of photobioreactors outdoors, on top of natural variations, microalgae are subjected to further complexity in light exposure. Because of the high-density cells experience self-shading effects that heavily limit light availability in most of the mass culture volume. This limitation strongly affects biomass productivity of industrial microalgae cultivation plants with important implications on economic feasibility. Understanding how photosynthesis responds to cell density is informative to assess functionality in the inhomogeneous light environment of industrial photobioreactors. In this work we exploited a high-sensitivity Clark electrode to measure microalgae photosynthesis and compare cultures with different densities, using Nannochloropsis as model organism. We observed that cell density has a substantial impact on photosynthetic activity, and demonstrated the reduction of the cell's light-absorption capacity by genetic modification is a valuable strategy to increase photosynthetic functionality on a chlorophyll-basis of dense microalgae cultures. • Microalgae biomass is a promising alternative to crops. • The impact of cultivation at scale on photosynthesis is still under-investigated. • The Photosynthesis-Irradiance (PI) relationship is informative. • High-sensitivity oxygen measurements for PI investigation was validated. • The effect of cell density on PI was studied in Nannochloropsis pale mutants. [ABSTRACT FROM AUTHOR]