Physicochemical and Bioactive Characterization of a Neotropical Calothrix Strain.

Despite the biotechnological potential of cyanobacteria, the antibacterial, antifungal, and prebiotic properties of the genus Calothrix remain largely unexplored. This study characterizes the composition and biological activity of a neotropical strain Calothrix sp. CBUCES-K 9914 from Antioquia, Colombia, and evaluates growth under varying light and nutrient treatments. The strain achieved its highest biomass yield (0.75 g L⁻¹) under white light supplemented with 0.3 g L⁻¹ glucose and 0.2 g L⁻¹ nitrogen. Characterization revealed 16 amino acids, dominated by aspartic acid (20.4%), alanine (14.5%), and glycine (13.9%), alongside high concentrations of sodium (3.30 mg g⁻¹) and calcium (2.90 mg g⁻¹). Antioxidant assays showed significant activity, particularly in the ORAC assay (118.2 ± 12.9 µmol TE g⁻¹). The strain significantly inhibited the growth of three pathogenic bacteria: Klebsiella pneumoniae ATCC 4352, Salmonella enterica ATCC 14028, and Staphylococcus aureus ATCC 6538; Kruskal-Wallis Tests: χ2 = 18.33-40.89, p < 0.01) and significantly suppressed growth in one yeast, Candida albicans ATCC 10231, beginning at hour 16 (χ2 = 17.8, p = 0.003) and persisting through hour 41 (χ2 = 16.48, p = 0.005). Conversely, it promoted the growth of two probiotic bacteria, Lactiplantibacillus plantarum and Limosilactobacillus reuteri, from hour 17 to 27.5 (χ2 = 11.48-21.33, p < 0.05). These findings highlight the biotechnological potential of strain Calothrix sp. CBUCES-K 9914 and warrant deeper investigation into the metabolite profile and the mechanisms underlying its antimicrobial and prebiotic activities.