# Cultivation of Arthrospira platensis in Veterinary Hospital Wastewater Enhances Pigment Production and Reduces Antibiotic Resistance Genes

## TL;DR

Arthrospira platensis can treat veterinary hospital wastewater by boosting pigment production and reducing antibiotic resistance genes.

## Contribution

This study demonstrates the dual use of Arthrospira platensis for wastewater treatment and pigment production in veterinary hospital wastewater.

## Key findings

- A. platensis cultivated in 25% VHW showed highest biomass and pigment production.
- Cultivation reduced Proteobacteria dominance and key antibiotic resistance genes in wastewater.
- The study shows A. platensis can simultaneously treat wastewater and produce valuable pigments.

## Abstract

Veterinary hospital wastewater (VHW) contains high levels of nutrients, organic pollutants, and antibiotic resistance genes (ARGs), posing environmental risks. This study investigated the potential of Arthrospira platensis for treating VHW. A. platensis was cultivated in different wastewater concentrations for 8 days. Growth and pigment production were highest in 25% VHW, while higher concentrations inhibited performance. In 25% VHW, pigment levels increased significantly compared to the control. Metagenomic analysis showed that cultivation of A. platensis in wastewater altered the microbial community and reduced both harmful bacteria and ARGs. The dominant bacteria group, Proteobacteria, decreased markedly after A. platensis cultivation in 25% VHW, which was also accompanied by a reduction in key resistance genes. These findings demonstrate that A. platensis can simultaneously treat wastewater and produce valuable pigments and biomass, providing a sustainable and environmentally friendly strategy for managing veterinary hospital effluents.

Veterinary hospital wastewater (VHW) is a significant environmental concern due to its high nutrient content, organic pollutants, and antibiotic resistance genes (ARGs). This study evaluated the physicochemical properties of VHW, its potential to support Arthrospira platensis cultivation, and its effects on microbial and resistome profiles. VHW contained high levels of ammonia nitrogen, total Kjeldahl nitrogen, biological oxygen demand (BOD), and chemical oxygen demand (COD), indicating substantial contamination. A. platensis was cultivated for 8 days in Zarrouk medium supplemented with 0–100% VHW. Biomass production peaked in 25% VHW (0.78 ± 0.05 g/L), while growth was strongly suppressed at concentrations ≥75%. Pigment levels in 25% VHW increased significantly compared to the control: 1.3-fold for chlorophyll-a (12.0 μg/mL), 1.5-fold for carotenoids (4.4 μg/mL), 1.7-fold for phycocyanin (120 μg/mL), and 2.3-fold for allophycocyanin (54 μg/mL). Shotgun metagenomic analysis revealed that A. platensis cultivation markedly altered the microbial community and reduced the prevalence of ARGs. In 25% VHW, Proteobacteria dominated the community (97.0%), but their abundance declined to 11.6% when co-cultivated with A. platensis. Likewise, Acinetobacter sp. carrying high levels of the aph gene, along with Methylophaga sp. and Pseudomonas_E sp. harboring oqxB, decreased substantially, suggesting that A. platensis effectively suppressed ARG-rich genera. These findings highlight the dual potential of A. platensis for sustainable pigment-rich biomass production and efficient wastewater treatment.