# Replacing Manual Operation with Bio-Automation II: Construction of a Biological Digestion Gene Circuit to Eliminate the Interference of Food Matrices in the Rapid Detection of Heavy Metals

## TL;DR

This paper introduces a biological digestion system that improves heavy metal detection in food by breaking down interfering compounds like phytic acid and starch.

## Contribution

A novel gene circuit was constructed to simultaneously detect mercury ions and digest food matrix components that interfere with detection.

## Key findings

- Biosensor responses improved 1.43-fold for phytate digestion in the presence of mercury ions.
- The detection limit of the BαAP biosensor was 0.082 μM for mercury ions.
- The biosensor's performance in real samples was significantly enhanced by the bio-digestion pathway.

## Abstract

Food matrices such as phytic acid, starch, and proteins can chelate heavy metals, acting as stabilizers that significantly hinder accurately detecting heavy metal contamination. This study proposes a biological digestion strategy to overcome such interference. The gene sequences for phytase (appA) from Escherichia coli (E. coli), α-amylase (amyA) from Escherichia coli (E. coli), and protease (AO090120000474) from Aspergillus oryzae were identified via bioinformatics screening. Whole-cell biosensors were then developed to simultaneously detect mercury ions (Hg2+) and digest phytate, starch, and proteins. In the presence of 100 μM Hg2+, biosensor responses improved by 1.43-, 1.38-, and 1.11-fold, respectively. A “heavy metal pollutant bio-digestion pathway” was constructed by integrating genes for synthesizing phytic acid, starch, and protein with those for Hg2+ detection. In the presence of 100 μM Hg2+, the detection effect was improved by 1.36-fold. The detection limit of the BαAP whole-cell biosensor was 0.082 μM, while the limit of quantitation was 0.272 μM. The study effectively addresses the limitations of biosensor performance in real sample detection.