# Single-Chamber Microbial Fuel Cell with an Innovative Sensing Component for Real-Time Continual Monitoring of a Wide Range of Cr(VI) Concentrations in Wastewater

## TL;DR

A new microbial fuel cell with a biosensor can monitor Cr(VI) in wastewater in real time, offering high accuracy and adaptability.

## Contribution

Integration of ChrA and ChrB genes into E. coli for real-time Cr(VI) monitoring in a microbial fuel cell.

## Key findings

- The biosensor detected Cr(VI) with a detection limit of 0.0075 mg/L and a response time of 20 s.
- It maintained accuracy (−1.73% to 2.5%) across Cr(VI) concentrations from 0.02 to 150 mg/L.
- The system operated effectively in a wide range of temperatures and pH levels.

## Abstract

Hexavalent chromium (Cr(VI)) is toxic, carcinogenic, and harmful to biological systems. Common detection methods, such as colorimetry, atomic absorption spectrometry, ion chromatography, and biological systems, can only be used in the laboratory and do not provide real-time feedback. To address these limitations, the current study cloned the ChrB gene, which exhibits high specificity in detecting Cr(VI), and the ChrA gene, which exhibits high Cr(VI) tolerance, into Escherichia coli. This recombinant strain, ChrA–ChrB–E. coli, was integrated into a single-chamber microbial fuel cell for accurate continual monitoring over a wide range of Cr(VI) concentrations. ChrA–ChrB–E. coli thrived in temperatures from 25 °C to 45 °C and pH levels between 5 and 8. Its ability to reduce Cr(VI) remained consistent across Cr(VI) forms, carbon sources, and oxyanions. Cyclic voltammetry was employed to verify the electrical activity of the biosensor. The biosensor exhibited a detection limit of 0.0075 mg/L. Under conditions simulating the regulatory emission limit for Cr(VI) of 0.5 mg/L in industrial wastewater, the biosensor achieved a response time of 20 s during continual operation. When tested with synthetic wastewater containing Cr(VI) concentrations from 0.02 to 150 mg/L, the system exhibited high adaptability and facilitated stable monitoring (relative standard deviation ≤ 2.7%). Additionally, the biosensor’s accuracy (−1.73% to 2.5%) matched that of traditional batch methods, highlighting its suitability for real-time Cr(VI) monitoring in aquatic environments.