An investigation on the effects of nanoplastic particles on Chlorella vulgaris enzymes and its function on removal of nitrate and phosphate

10.55434/CBI.2023.20102

Abstract

Plastic waste at sea has been a primary environmental concern for years. The degradation of plastics into small pieces leads to the formation of nanoplastics (NPs) (less than 100 nm) that can enter the environment. Polystyrene is one of the most common plastics, a product of the polymerization of styrene monomers. In this study, the toxic effects of amino polystyrene (PS-NH₂) NPs with sizes 90 (PS-NH₂-90), 200 (PS-NH₂-200), and 300 (PS-NH₂-300) nm with four different concentrations after  72 hours on viability, activity of enzymes such as superoxide dismutase (SOD), catalase (CAT), glutathione S-Transferase (GST) and reduced glutathione (GSH), carbonyl protein and sulfhydryl protein and antioxidant activity assay by DPPH reagent on the Chlorella vulgaris were investigated. In all enzymatic assays, except the glutathione (GSH) and sulfhydryl protein, the size of 90 nm showed lowest value. Intriguingly, flow cytometry assessment showed a substantial reduction in the viability at PS-NH₂-90 treated samples for 72 h which means that as the size of the nanoplastic decreases, its toxicity will increase. The toxicity effect of 90 nm NPs with a concentration of 200 mg/L on the microalgae C. vulgaris (with a concentration of 25000 Cells/mL) with the aim of bioremediation of nitrate (with a concentration of 50 mg/L) and phosphate (with a concentration of 6 mg/L) were investigated. According to the obtained results, NPs with a concentration of 200 mg/L with a size of 90 nm have the highest toxicity on the nitrate and phosphate bioremediation by the C vulgaris with a concentration of 25000 Cells/mL.