Adaptive Responses and Biochemical Changes of the Microalga Chlorella sorokiniana under Combined Antibiotic Stress

Bahador, Sussan; Zamani, Hajar

doi:10.22124/japb.2026.33815.1591

Adaptive Responses and Biochemical Changes of the Microalga Chlorella sorokiniana under Combined Antibiotic Stress

Articles in Press

Document Type : Research Paper

Authors

Sussan Bahador ¹
Hajar Zamani ²

¹ Department of Biology, College of Science, Shiraz University, Shiraz, Iran

² Biology Department , School of Science, Shiraz University, Shiraz, Iran

10.22124/japb.2026.33815.1591

Abstract

The global increase in population has led to a substantial rise in the consumption of antibiotics worldwide. Approximately 70% of these pharmaceuticals are excreted unchanged through urine and feces, entering wastewater systems and subsequently being released into aquatic environments. These emerging contaminants not only contribute to the development of bacterial and fungal resistance but also adversely affect non-target organisms, including microalgae and cyanobacteria. As primary producers in aquatic food webs, these microorganisms play a crucial ecological role, and any disruption in their growth and biodiversity may threaten ecosystem stability. In the present study, the physiological and biochemical responses of the microalga Chlorella sorokiniana to combined exposure to vancomycin and ampicillin at different concentrations (0.1, 1, 2.5, and 5 g L⁻¹) were investigated over time. The results showed that cell density increased over the experimental period in all treatments. However, exposure to the highest antibiotic concentration (5 g L⁻¹) reduced microalgal growth by approximately 50% after five days. Carotenoid content increased by 76% at 5 g L⁻¹, whereas chlorophyll content did not differ significantly from that of the control. In contrast, total lipid content decreased by 46% at the same concentration, while protein and carbohydrate contents remained unchanged compared with the control. In addition, the levels of phenolic compounds and antioxidant capacity were evaluated. The results indicated that combined antibiotic exposure enhanced the accumulation of non-enzymatic antioxidant compounds in C. sorokiniana, and antioxidant capacity increased in a concentration-dependent manner. These findings improve our understanding of the physiological and biochemical responses of microalgae to combined antibiotic stress and provide valuable baseline information for assessing the ecological risks of antibiotic contamination as well as for developing microalgae-based strategies for environmental monitoring and wastewater treatment.

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