Functional groups in microalgal extracellular polymeric substances: A promising biopolymer for microplastic mitigation in marine ecosystems

This study aims to characterise the amounts of EPS produced and the chemical functional groups of three different microbial phyla, namely Chlorophyta (Dunaliella sp.), Bacillariophyta (Phaeodactylum sp.), and Cyanobacteria (Spirulina sp.).Microalgae of Dunaliella sp., Phaeodactylum sp. and Spirulina sp. were grown in culture media with continuous aeration and lighting and controlled temperature.At the beginning of the stationary phase, the culture medium was centrifuged, ethanol precipitated, dialysed with deionised water and freeze-dried to produce white EPS biopolymer.The dry EPS weight of microalgae Dunaliella sp., Phaeodactylum sp. and Spirulina sp. were 0.3560.01gL -1 , 0.2450.02gL -1 and 0.4770.02gL -1 , respectively.In the present study we used micro scopic Fourier-Transform Infrared Spectroscopy (FTIR) to investigate functional group of EPS microalgae.The Fourier Transform Infrared (FTIR) spectra of all three exopolysaccharides (EPS) reveal key similarities, including O-H stretching vibrations around 3500 cm, indicative of hydroxyl groups that enhance hydrophilicity, and C=O stretching vibrations between 1700-1600 cm, suggesting the presence of carbonyl groups.These functional groups, along with C-H stretching vibrations around 2920-2850 cm linked to aliphatic hydrocarbons, contribute to the structural integrity, solubility, and versatility of EPS in biological and industrial applications.The study concludes that EPS-producing microalgae hold significant potential for mitigating microplastic pollution through aggregation and possible biodegradation, especially in marine environments.