Cultivation of the macrophyte Lemna minor and the microalgae Chlorella sorokiniana in thermal mineral waters: Biomass characteristics, radioisotopes and heavy metals content

• Published in: Environmental pollution (1987) 2024-05, Vol.349, p.123881, Article 123881
• Main Authors: Katsara, Alexandra, Zkeri, Eirini, Aloupi, Maria, Pappa, Filothei K., Matsoukas, Christos, Stasinakis, Athanasios S.
• Format: Article
• Language: English
• Subjects: Biomass characterization; Heavy metals; Macrophytes; Microalgae; Radioactivity; Thermal mineral springs water
• ISSN: 0269-7491; 1873-6424; 1873-6424
• DOI: 10.1016/j.envpol.2024.123881

Microalgae and macrophytes are commonly used as human and animal food supplements. We examined the cultivation of the microalgae Chlorella sorokiniana and the duckweed Lemna minor in thermal waters under batch and sequencing batch conditions and we characterized the produced biomass for the presence of essential nutrients as well as for heavy metals and radioisotope content. The highest specific growth rate for the microalgae was observed when 5 or 15 mg/L N were supplemented while the optimal conditions for Lemna minor were observed in the co-presence of 5 mg/L N and 1.7 mg/L P. Lemna minor presented higher concentrations of proteins and lipids comparing to the studied microalgae. Both organisms contained high amounts of lutein (up to 1378 mg/kg for Lemna minor) and chlorophyll (up to 1518 mg/kg for Lemna minor) while β-carotene and tocopherols were found at lower concentrations, not exceeding a few tens of mg/kg. The heavy metal content varied between the two species. Lemna minor accumulated more Cd, Cu, K, Mn, Na, Ni, and Zn whereas Al, Ca and Mg were higher in Chlorella sorokiniana. Both organisms could be a significant source of essential metals but the occasional exceedance of the statutory levels of toxic metals in food products raises concern for potential risk to either humans or animals. Application of gamma-spectroscopy to quantify the effective dose to humans from 228Ra, 226Ra and 40K showed that Chlorella sorokiniana was well under the radiological limits while the collected mass of Lemna minor was too small for radiological measurements with confidence. [Display omitted] •Chlorella sorokiniana and Lemna minor cultivation in thermal waters.•Higher concentration of proteins, lipids, lutein and chlorophyll in Lemna biomass.•Both organisms are substantial source of Ca, Cu, Fe and Zn for humans and animals.•Pb in Lemna minor was above the maximum level set by EU for food supplements.•Chlorella sorokiniana was found to be well under the radiological limits.