Reasonable design of the chargeability of Escherichia coli amyloid nanofiber CsgA for efficient adsorption of polystyrene microplastics in water

Abstract:

[Background] With the progress in industrialization, microplastics causing "white pollution" have gradually become one of the main environmental pollutants. As an emerging microplastic adsorption method in recent years, microbial remediation of microplastics in water has important practical significance. [Objective] We modified CsgA to make the strain expressing the modified protein have the ability to efficiently remove microplastics and studied the influencing factors and mechanism of its adsorption of polystyrene (PS), aiming to provide reference for microbial remediation of microplastics. [Methods] After mutation of the negatively charged aspartic acid (D) on the R₂-R₄ structural unit of CsgA to positively charged arginine (R), the isoelectric point of the protein was increased. Accordingly, the protein surface had more positive charges, thereby binding with negatively charged microplastics to achieve the purpose of water restoration. The main factors (pH, initial concentration, temperature, etc.) affecting the PS adsorption capacity of the strain expressing modified CsgA were investigated, and the adsorption mechanism was discussed via isothermal adsorption models and kinetic analysis. [Results] Compared with CsgA, D104R/D127R increased the PS adsorption efficiency by 1.37 times from 40.88% to 97.08% and the adsorption capacity by 3.59 times from 1.27 g/g to 5.83 g/g. D104R/D127R demonstrated good PS adsorption ability within the range of pH 3.0 to pH 10.0. The adsorption of PS by D104R/D127R complied with the Freundlich isothermal adsorption model, which indicated multi-molecular layer adsorption. [Conclusion] D104R/D127R has a good ability to remove PS, and the research results on the influencing factors and mechanism of PS adsorption provide guidance for microbial remediation of microplastics pollution.