# Machine Learning-Enhanced MEC Sensors with Feature Engineering for Quantitative Analysis of Multi-Component Toxicants

## TL;DR

This paper introduces a new method using microbial electrochemical systems and machine learning to accurately detect and quantify multiple toxicants in complex mixtures.

## Contribution

The novel integration of mechanism-driven feature engineering with machine learning in microbial electrochemical systems for multi-component toxicant analysis.

## Key findings

- Random Forest (RF) achieved R² > 0.9 for all tested toxicants with high accuracy.
- Geobacter anodireducens and Comamonas testosteroni were identified as key functional taxa in the microbial community.
- The framework enables rapid and low-cost monitoring of mixed toxicants with minimized error metrics.

## Abstract

Accelerated industrialization has caused complex mixed toxicant pollution, where synergistic or antagonistic interactions render conventional detection methods inadequate. Herein, we develop an integrated framework by pioneering the integration of microbial electrochemical systems (MECs) with machine learning (ML) for quantifying formaldehyde, tetracycline, Ag+, and Cu2+ in multi-component, multi-ratio, and multi-concentration mixtures. MECs generated dynamic current–time (I–t) signals responsive to toxicant stress, though signal overlap from mixed toxicants hindered direct quantification. Guided by toxicokinetics and electrochemical mechanisms, we developed a novel mechanism-driven feature engineering strategy with exclusively original indicators, which extracted 22 multidimensional features capturing instantaneous characteristics, kinetic patterns, and microbial stress-adaptive responses to resolve signal ambiguity, and provided biologically meaningful, high-information feature inputs that effectively bridge electrochemical response signals and ML modeling. Comparative analysis of four ML models (SVM, KNN, PLS, and RF) showed RF outperformed others, achieving R2 > 0.9 for all toxicants (formaldehyde: 0.959; tetracycline: 0.934; Ag+: 0.936; Cu2+: 0.957) with minimized MAE and RMSE. Microbial community analysis identified Geobacter anodireducens (71.5%, electroactive for heavy metals) and Comamonas testosteroni (12.9%, organic degrader) as key functional taxa, supported by KEGG enzyme abundance data. This work overcomes traditional MEC limitations via innovative feature engineering and pioneering ML integration, providing a rapid, low-cost, and high-accuracy tool for environmental mixed toxicant monitoring.