Hidden inside desert rocks: Salinity triggers an increase in exopolysaccharides from endolithic cyanobacteria with anti-inflammatory potential

Abstract

Endolithic cyanobacteria thriving in rocks of deserts remain an unexplored source for the quest of novel bioproducts in extreme environments. In this work, 7 endolithic cyanobacteria from the polyextreme Atacama Desert, covering four genera and three lithic substrates, were investigated for the production of exopolysaccharides with anti-inflammatory potential. A moderate salinity (20 g NaCl L⁻¹) was tolerated by all strains, triggering a 3–9-fold increase in exopolysaccharides (EPS) yield in 4 of them that counteracted the growth decrease due to NaCl stress. EPS from all strains showed anti-elastase activity with inter-strain and inter-salinity variations. The moderate EPS productivity by Gloeocapsa sp. UAM572 (0.4 mg EPS L⁻¹ day⁻¹), elevated anti-elastase capacity of Chroococcidiopsis sp. UAM579 EPS (IC₅₀ = 78 μg mL⁻¹) and the first biotechnological data of genus Pseudoacaryochloris, provide a promising foundation for potential applications of EPS from endolithic cyanobacteria in cosmetics and biomedicine, whose opportunities and challenges are discussed herein.