Speciation-Dependent Arsenic Stress Responses in Chlorella sorokiniana (PX796505): Physiological Resilience, Biochemical Reprogramming, and Implications for Sustainable Bioremediation and Circular Bioeconomy

Arsenic contamination poses a serious threat to aquatic ecosystems and human health worldwide. Microalgae offer a sustainable alternative to conventional remediation methods. This study investigates speciation-dependent arsenic stress responses in Chlorella sorokiniana (PX796505) exposed to arsenite [As(III)] and arsenate [As(V)]. Cultures were subjected to 0–125 mg L⁻¹ arsenic for 28 days. Growth, biomass productivity, photosynthetic pigments, ultrastructure, biochemical composition, and arsenic removal efficiency were evaluated. Chlorella sorokiniana exhibited distinct physiological and metabolic responses to the two arsenic species. Arsenite caused strong early growth inhibition, chlorophyll loss, and severe ultrastructural damage, reflecting its higher cytotoxicity. Partial acclimation occurred at later stages. In contrast, arsenate showed lower toxicity and induced hormetic effects, sustaining growth and photosynthetic efficiency even at high concentrations. Arsenate stress promoted lipid and carbohydrate accumulation, indicating metabolic reprogramming toward stress tolerance and carbon storage. Arsenic removal efficiency reached 64.0% for As(III) and 81.5% for As(V), demonstrating superior phycoremediation of pentavalent arsenic. Biochemical analyses revealed stress-induced enrichment of lipids, proteins, and carbohydrates, enhancing biomass valorization potential. Overall, C. sorokiniana shows strong resilience to arsenic stress and effective arsenic removal, particularly for As(V). The results support its application in sustainable phycoremediation coupled with circular bioeconomy-driven biomass utilization.