Characterization of Bioactive Metabolites in Phormidium sp. PB21: Pigment Production, Antimicrobial Potential, and Toxicity Assessment.

This study investigates the morphological characteristics, pigment production, antimicrobial activity, and toxicity of secondary metabolites from the filamentous cyanobacterium Phormidium sp. PB21, isolated from freshwater ecosystems. The strain demonstrated significant potential for bioactive compound production, as evidenced by its chlorophyll-a and carotenoid production. Chlorophyll-a levels increased at 0.071 mg/mL by day 24, reflecting robust photosynthetic activity, while carotenoid content reached a maximum of 1.6 mg/mL under controlled conditions, highlighting its potential for pigment-based applications. Antimicrobial assays using methanol: chloroform (1:3) crude extracts revealed inhibition of human pathogens, including Serratia sp. (12 mm) and Pseudomonas aeruginosa (11 mm), with minimum inhibitory concentrations as low as 15.6 µg/mL for specific fractions. Toxicity assessment using Artemia salina indicated dose-dependent effects, with LC50 values of 93 and 82 µg/mL for fractions 3 and 4, respectively, suggesting potential as natural bioactive agents. The gas chromatography-high-resolution mass spectrometry analysis of the sample identified key bioactive compounds, including decanoic acid, 5-acetoxytridecane, and 1-undecanol, based on their characteristic m/z values. These compounds exhibit potential antimicrobial, anti-inflammatory, and pharmacological properties, highlighting the sample's promising therapeutic and industrial applications. These findings emphasize the biotechnological potential of Phormidium sp. PB21, particularly in antimicrobial and pigment production applications.