Elucidating the cellular adaptive response of Coccomyxa sp. upon exposure to PVC-nanoplastics (PVC-NPs) for production of bioenergy molecules

Abstract

Nanoplastics (NPs) have emerged as a persistent pollutant in aquatic bodies with significant ecological implications. Polyvinyl chloride (PVC), despite being a widespread halide-containing synthetic polymer and ranked amongst the most toxic plastic types, has been understudied concerning its long-term toxicity, especially in its nanoform. Microalgae, being the primary producers, serve as toxicity indicators in the aquatic ecosystem. Hence, this study assessed the physiological effects of PVC-NPs at 10, 50, and 100 ppm concentrations on Coccomyxa sp. IITRSTKM4 over 14 days. PVC-NPs induced a 42% reduction in growth at 100 ppm along with increased cell aggregation and altered morphology. SEM-EDX and FTIR analysis confirmed the adsorption of PVC-NPs onto the microalgal surface. Further, oxidative stress was evidenced through elevated ROS, leading to enhanced lipid peroxidation and reduced photosynthesis. In response, the microalgae exhibited elevated levels of glycine betaine and antioxidant enzymes, denoting the adaptive, responsive mechanism of Coccomyxa sp. to PVC-NPs. Alongside this, a ∼1.2 to 1.3-fold rise in lipid and carbohydrate content was noted at 50 ppm. Concurrently, nearly a 1.6-fold increment in secretion of extracellular polymeric substances (EPS) was observed, which is instrumental in hetero-aggregate formation. This study highlights the physiological resilience of the freshwater microalga Coccomyxa sp. to PVC-NPs, underpinning its behavioral and adaptive response to environmental contaminants, while unveiling promising avenues for sustainable remediation and bioenergy production.