Characterization of cyanobacterial mats from an artificial hot spring in Uniejów (Poland) and the potential use of their biomass

Artificial geothermal water systems are an efficient and low-cost alternative to natural ecosystems for phototrophic microorganism biomass production on an industrial scale. Our study focused on the investigation of mat-forming cyanobacteria produced in an artificial pool with a geothermal water source from a hot spring in Uniejów, Poland. The microorganisms inhabiting this ecosystem tolerate the high salinity (approximately 50 ‰) and temperature (45-55.2 °C) of the water. The structure, composition, and growth rates of the cyanobacterial mats were investigated under natural and laboratory conditions. We tested whether cyanobacteria harvested from this habitat represent a safe source of vital biomolecules for industrial applications. We found that the layered mats consisted of simple filamentous cyanobacteria, mainly of the genera Leptolyngbya, Thermoleptolyngbya, and Anagnostidinema. In the isolated cyanobacteria, we did not detect commonly studied cyanotoxins (i.e., ATX-a, BMAA, CYN, MC, and SXT) that could pose a direct risk to human health and lead to indirect risks through the contamination of bioproducts. The extracts and filtrates of the strains did not reduce the survival of Daphnia. In addition, we found that temperatures of 40-50 °C and pH values of 7.2-7.7 were optimal for mat formation and the growth of the dominant cyanobacteria. In the case of the Desertifilum dzianense strain, the highest biomass yield was noted at 26 °C. In summary, our study indicates that mat-forming cyanobacteria inhabiting ecosystems powered by geothermal waters from the Uniejów hot spring have strong potential as bioresources for different industrial applications.