A whole-cell electrochemical biosensing system based on bacterial inward electron flow for fumarate quantification.

Fumarate is of great importance as it is an oncometabolite as well as food spoilage indicator. However, cost-effective and fast quantification method for fumarate is lacking although it is urgently required. This work developed an electrochemical whole-cell biosensing system for fumarate quantification. A sensitive inwards electric output (electron flow from electrode into bacteria) responded to fumarate in Shewanella oneidensis MR-1 was characterized, and an electrochemical fumarate biosensing system was developed without genetic engineering. The biosensing system delivered symmetric current peak immediately upon fumarate addition, where the peak area increased in proportion to the increasing fumarate concentration with a wide range of 2 μM-10 mM (R(2)=0.9997). The limit of detection (LOD) and the limit of quantification (LOQ) are 0.83 μM and 1.2 μM, respectively. This biosensing system displayed remarkable specificity to fumarate against other possible interferences. It was also successfully applied to samples of apple juice and kidney tissue. This study added new dimension to electrochemical biosensor design, and provide a simple, cost-effective, fast and robust tool for fumarate quantification.