# Cultivation of Anabaena sp. at Different Phosphorus Excess Concentrations: Growth Parameters, Value‐Added Metabolites, and Microcystin‐LR Production

## TL;DR

This study explores how different phosphorus levels affect the growth and chemical production of Anabaena sp., finding that higher phosphorus boosts beneficial compounds and antibacterial properties.

## Contribution

The study reveals that Anabaena sp. produces both toxins and valuable antibacterial/antioxidant metabolites under phosphorus excess, suggesting new drug development potential.

## Key findings

- Higher phosphorus levels increased chlorophyll a and carotenoid contents in Anabaena sp.
- Anabaena sp. extracts showed antibacterial activity against Escherichia coli and Staphylococcus aureus.
- The cyanobacteria produced several antioxidant and antibacterial biomolecules identified via GC/MS analysis.

## Abstract

Phosphorus is a key driver of cyanobacterial proliferation and the production of secondary metabolites in freshwater ecosystems. In this study, the effects of different phosphorus concentrations, including 7.10 (control treatment), 7.74, 8.38, and 9.66 mg L−1 (CP230, TP250, TP271, and TP312, respectively), on growth, valuable biochemicals, as well as the toxicity potential of Anabaena sp. in BG‐11 medium were investigated. Elevated phosphorus levels significantly enhanced chlorophyll a and total carotenoid contents, with the highest values recorded under 8.38 mg P L−1 (1.16 ± 0.04 mg L−1 and 1.07 ± 0.30 mg L−1, respectively). This treatment also yielded the greatest total phenolic content (8.04 ± 0.32 mg GAE g−1 DW−1) and antioxidant activity (IC50 = 2.98 ± 0.02 mg mL−1). Antibacterial assays demonstrated notable inhibition zones against
Escherichia coli
(9.30 ± 1.20 mm) and
Staphylococcus aureus
(4.50 ± 0.90 mm) in the treatment with 8.38 mg P L−1. GC/MS analysis showed that the cyanobacterial extracts contained several biomolecules such as phenol, 2,4‐Di‐tert‐butylphenol, hexadecanoic acid methyl ester, and other compounds with antioxidant and antibacterial activity. Palmitic acid, palmitoleic acid, oleic acid, and linoleic acid were the dominant fatty acids in the lipid profile of Anabaena sp. In addition to its antibacterial properties, Anabaena sp. showed moderate to low toxicity against
Daphnia magna
, depending on the phosphorus concentration of the treatments. The findings of the current research indicated that Anabaena sp. not only produces cyanotoxins but also beneficial chemicals, positioning it as a potential new target for antibacterial and antioxidant drug development.