Microbial community and dynamic changes of extracellular polymeric substances in relation to plastisphere of disposable surgical masks in natural aquatic environment

In the context of global COVID-19 epidemic preparedness, the extensive use of disposable surgical masks (DSM) may lead to its emergence as a main new source of microplastics in the environment. Nowadays, DSMs have become a non-negligible source of plastic waste in aquatic environment, however, less research has been done on DSM after biofilm colonization in freshwater environment. The study investigated the microbial community of DSM-associated biofilms by 16S rRNA gene sequencing. Analysis of the microbial community in the middle and inner/outer layers of the DSM showed that the middle layer was different from the remaining two layers and that potential pathogens were enriched only in the middle layer of the DSM. Herein, we focused on the middle layer and explored the characterization properties and extracellular polymeric substances (EPS) components changes during biofilm formation. The results showed that the EPS components varied with the biofilm incubation time. As the formation of biofilm, the protein (PN) and polysaccharide (PS) in EPS showed an overall increasing trend, and the growth of PS was well synchronized with PN. Three fluorescent components of EPS were determined by the three-dimensional excitation emission matrix (3D-EEM), including humic acid-like, fulvic acid-like, and aromatic protein-like components. The percentage of fluorescent components varied with increasing biofilm development time and then stabilized. Fourier transform infrared spectroscopy (FTIR) characterization results elucidated the emergence of oxygen-containing functional groups during biofilm formation. Moreover, the hydrophilicity increased with biofilm development. In conclusion, the environmental behavior and ecological risks of DSM in aquatic environment deserve urgent attention in future studies.