Comparative Evaluation of Arthrospira platensis Cultivation in Closed Tubular Photobioreactors Versus Open Systems

Abstract

Background: Arthrospira platensis (Spirulina) is a nutrient-rich cyanobacterium widely cultivated for high-value applications in food, pharmaceuticals, and biotechnology, with production increasingly shifting toward controlled photobioreactor systems to enhance biomass quality and yield. Aims: To evaluate the cultivation efficiency of the cyanobacterium Arthrospira platensis in a closed tubular photobioreactor (PBR) compared to a conventional open system. Study Design: Experimental, comparative study. Place and Duration of Study: Institute of Life Sciences, Vietnam Academy of Science and Technology, Ho Chi Minh City, Vietnam, between March and July 2025. Methodology: The growth efficiency of Arthrospira platensis was compared in closed tubular PBR and conventional open system. Initial trials were done to determine the optimum inoculum concentration. Four closed PBR configurations were tested to determine the most efficient model for mixing and mass transfer. Results: The best inoculum concentration was 0.30 g/L. The most effective configuration was the closed PBR with tubes in series with 30° tilt from the horizontal plane (system 4). The closed PBR was significantly more efficient than the open system, reaching a maximum biomass concentration of 3.50 g/L after 7 days, which was 2.65 times higher than the open system (1.32 g/L on day 14). The average biomass productivity in the closed PBR was 0.457 g/L/day which was 6.26 times higher than the open system. The closed system also enhanced the accumulation of biochemical compounds: protein (59.21%), chlorophyll (15.11 mg/g), phycocyanin (123.37 mg/g), and carotenoids (4.03 mg/g). Conclusion: The closed tubular photobioreactor is a robust empirical foundation for improving both the productivity and the biochemical quality of A. platensis biomass in Vietnam compared to open systems.