Abstract
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.