Response mechanism of extracellular polymers in the remediation of chromium pollution by carbonate mineralizing bacteria

Abstract

This study examines the adaptability of carbonate mineralizing bacteria in Cr(III)-contaminated environments with varying Cr(III) concentrations and their response mechanism via EPS. Cr(III) removal efficiency declined with concentrations exceeding 1000 mg L⁻¹, while the removal amount continued to rise, indicating strong Cr(III) tolerance in the bacterium. Analysis of dynamic changes in EPS revealed a significant increase in production, with polysaccharides and proteins playing key roles in Cr(III) binding. A notable increase in mannose in the monosaccharide composition of EPS suggests its involvement in Cr(III) binding. Moreover, alterations in the protein secondary structure, such as a reduction in α-helix content and an increase in β-sheet and random coil structures, may enhance EPS interaction with Cr(III). These findings demonstrate that EPS contributes to heavy metal remediation not only through its polysaccharide components but also through changes in protein structure, offering a new theoretical foundation for Cr(III) bioremediation.