Exploring biochemical responses and cellular adaptations of Chlorella sorokiniana to polyethylene microplastic exposure

Microplastics (MPs) are a common long-lasting pollutant of aquatic ecosystems. Microalgae are primary producers of aquatic systems, and MP contamination could have a high impact on the aquatic food web. Therefore, the present study utilized polyethylene (PE) particles (0 to 150 mg/L) for investigating the half-maximal inhibitory concentrations (IC₅₀) of Chlorella sorokiniana and also studied their impacts on growth rate, biomass, pigments and other biochemical components of the microalgae. After 96 h of incubation, PE of 100 mg/L resulted in the half-maximum inhibition (IC₅₀). After reaching the stationary phase (14 d), harvesting was made for MP-exposed cultures to reveal a biomass production of 0.89 g/L, while it was 0.96 g/L for the control. A slight reduction in pigment and lipid contents was also observed, while the protein and carbohydrate contents were high in MP-exposed C. sorokiniana cells. Under the MP stress, reactive oxygen species (ROS) and phenolic levels were reduced, whereas flavonoid content increased. PE particles were characterized using Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy (SEM-EDX) and Fourier Transform infrared spectroscopy (FT-IR) for their size, shape, chemical composition, and interaction with C. sorokiniana, followed by micro-Fourier Transform infrared spectroscopy (µ-FT-IR) for the mapping of MP. This research contributes to a deeper understanding of how MP contamination can disrupt aquatic food webs, guiding future ecological assessments and pollution management strategies.