Airborne transport and characterization of microalgal bioaerosols generated in raceway and tubular photobioreactors

The increasing demand for natural products has attracted special attention to microalgal biomass, which is often cultivated in open ponds. These systems are vulnerable to biological contamination, which reduces both the yield and quality of the biomass. The contamination process, particularly through airborne transport of unwanted microalgae, fungi, or bacteria, is poorly understood. In this study, bioaerosols were collected in quartz filters through a low-volume sampler located at different locations at the CIESOL demonstration plant (Almeria, Spain). The samples were analysed using metagenomics and SEM-EDS to assess the number of cells and the microbial diversity of the filters. The results revealed airborne transport of microalgae across different locations, with a gradual decrease in cell numbers as the distance from the source increased ( p < 0.05). Additionally, although different microalgal strains were detected in the filters, the most abundant belonged to the Chlorellaceae family. The results of this study highlight, for the first time, that the paddlewheels of raceway ponds and the bubbling columns of tubular reactors act as significant sources of bioaerosols, which have the potential to travel considerable distances and contaminate open ponds and even closed photobioreactors. • Airborne transport of microalgae across different locations • The paddlewheels of raceways act as sources of bioaerosols. • Tubular photobioreactors and vertical columns are sources of bioaerosols. • SEM-EDS analysis enabled the visualization of individual microalgae particles. • Microalgae potential to contaminate open and closed systems.