Biodegradation of polystyrene microplastics by Pseudomonas sp. WD23: Toxicity assessment using freshwater snail Pomacea canaliculata

This study presents degradation of polystyrene microplastics (PS MPs) by petroleum hydrocarbon degrading Pseudomonas sp. WD23 and toxicity assessment on Pomacea canaliculata. Exposure of 100 mg/L PS MPs to Pseudomonas sp. WD23 for 42 days, led to 28.40 ± 0.57 % weight reduction, following first order kinetics with rate constant and half-life of 0.0073 day⁻¹ and 94.95 days. Scanning electron microscopy and Fourier transform infrared spectrometry analysis revealed bacterial biofilm presence, smoothening, hole formation with confirmed oxidative degradation. Comparative toxicity of 100 and 200 mg/kg sediment of pristine and degraded PS MPs on Pomacea canaliculata was analyzed by behavior, mortality, enzymatic and non-enzymatic stress responses. Contact with pristine PS MPs caused increased reaction time with marked catalase (0.0095–0.0113 mmol/(min·mg protein)) and radical scavenging activity (73.68–78.96 %). Exposure to degraded PS MPs yielded slight catalase (0.0029–0.0032 mmol/(min·mg protein)) and moderate radical scavenging activity (63.15–65.78 %).