Hot springs cyanobacteria endowed with biological activities for cosmetic applications: Evaluation of on-site collected communities and isolated strains

stract Microbial communities growing around hot springs (bioglea), of which cyanobacteria are the main components, contribute to beneficial properties of thermal muds and often enter cosmetic treatment products. Bioglea is obtainable via alternative approaches to harvesting from nature: direct cultivation of whole communities and isolation and cultivation of the isolated strains. Cultivation represents a step towards industrial production, guaranteeing higher availability, quality and safety. In this work, the biochemical composition of natural and cultivated bioglea collected in different hot springs and of cyanobacterial strains isolated thereof was analysed. Lipophilic and hydrophilic extracts were tested for antimicrobial and radical scavenging activities and toxicity against Artemia salina. Higher antimicrobial activity was found in lipophilic than hydrophilic bioglea extracts and the opposite in isolates’ extracts. Thermal water extracts also showed some activity. No toxicity was observed. Bioglea radical scavenging activity positively correlated with carotenoids (lipophilic extracts) and phycobiliproteins (hydrophilic extracts). No correlation was observed for isolated strains. Cultivation at the 10 L scale of Chroococcidiopsis BIOG3 evidenced bioactivity changes with the growth phase and life cycle stage. From activity comparison, communities showed higher potential over single strains cultivation; however, further investigations should elucidate isolates’ full potential also by combining them into synthetic communities to simplify production and standardisation.