Marine microalgae – Mediated biodegradation of polystyrene microplastics: Insights from enzymatic and molecular docking studies

Abstract

Biodegradation of microplastics (MPs) through microalgal strains would be of eco-friendly approach for significant pollution abatement. Polystyrene (PS) is a major contaminant in the marine environment; however studies on marine microalgal degradation of PS MPs have been very limited. In the present study, six marine microalgal strains viz. Picochlorum maculatum, Dunaliella salina, Amphora sp., Navicula sp., Synechocystis sp. and Limnospira indica were investigated for their ability to degrade PS MPs for the incubation period of 45 days. Results from weight reduction, ATR-FTIR, SEM, and molecular docking analysis confirmed that microalgae formed biofilms on PS MPs, causing structural changes, and laccase-driven enzymatic breakdown. A maximum weight loss of 23.2 ± 0.21% and a minimum of 11.3 ± 0.026% were caused by the colonized microalgae Synechocystis sp. and Amphora sp. respectively. The study indicated that a higher reduction rate was observed in the Synechocystis sp. Treated PS MPs with a rate of 0.0058 g/day and a lower half-life of 119.34 days. SEM analysis showed that microalgae caused pits, erosion, and damage to the PS film. ATR-FTIR confirmed the chemical modifications and proved biodegradation. Laccase enzyme activity was higher in Synechocystis sp., and molecular docking showed the laccase interaction with the derivatives of PS, elucidating the breakdown process. This study highlights the potential of microalgae for eco-friendly microplastic degradation and paves the way for future research on the by-products of this process. Exploring the ecological impact of by-products and optimizing scalable methods can further enhance the sustainability and practical applications of this promising solution.