Comparative evaluation of an electrochemical bioreporter for detecting phenolic compounds

In this study, we constructed an Escherichia coli-based electrochemical bioreporter (EB) harboring pLZCapR, which encodes the CapR regulatory protein (for phenol degradation) along with β-galactosidase, and examined its ability to detect phenolic compounds as compared with previously reported optical bioreporters (OBs) controlled by CapR and detected using a luminometer (OB-lum) or spectrophotometer (OB-spec). The recombinant E. coli bioreporter cells were immobilized in polyvinyl alcohol (PVA); p-aminophenyl-β-D-galactopyranoside (PAPG) was used as the enzymatic substrate; and electrochemical measurements were taken. The peak current obtained on cyclic voltammetry (CV) was used to measure the redox response of PAPG degradation. Our results revealed that the EB system showed a detection range of 10 nM to 10 mM phenol with a good lower detection limit (30 nM phenol). Furthermore, the detection time was dramatically lower for the EB system (15-20 min) compared to the OBs (∼ 6 hr). These responses were reliably repeatable with an acceptable standard deviation (± 2.7%; n = 6), and the system showed good stability without loss of activity over 7 hr of operation or following 2 weeks of cold storage. Together, these results show that the EB system is faster and has a lower detection limit than the existing optical techniques.