Intracellular bioaccumulation outperforms surface display: A superior strategy for sustainable arsenic bioremediation...

Arsenic contamination in water poses a serious threat to public health, potentially causing various health issues. Therefore, effective remediation technologies are needed to remove arsenic contamination from water. In this study, we developed a whole-cell bioremediation system for simultaneously and efficiently removing As(III) and As(V) from water. By knocking out the arsenic efflux pump gene (arsB) and optimizing the expression of arsenic-binding protein ArsR and arsenate reductase ArsC, we engineered bacterial strains capable of sequestering arsenic within the cells. We systematically compared the remediation performance of the arsenic-inducible (MT022) and constitutive expression (MT047) systems in both free-cell and biofilm states. Both strains achieved over 96% removal of 10 μg/L As(III) and As(V) within 5 h. Even at a higher concentration of 100 μg/L, the constitutive strain MT047 maintained 76.2% removal for As(III) and 55.9% for As(V). While slower than chemical adsorbents, this demonstrates significantly faster kinetics than previous biological systems which typically require 20-24 h to achieve similar removal efficiencies. While both systems performed equally well in the free-cell state, the constitutive expression system MT047 demonstrated superior adsorption capacity in the application of biofilms achieving a 71.8% removal of 100 µg/L As(III) within 24 h. Contrary to conventional favoring surface display systems, our findings revealed that intracellular expression of ArsR and ArsC proved more effective for arsenic bioremediation. To address the application challenges, we have developed a "plug-and-play" biofilm platform that simplifies the operational procedures and provides a safe, efficient solution for treating arsenic-contaminated water. This study offers a promising strategy for comprehensive arsenic pollution control with potential for real-world applications.