Rapid, Sensitive, and Specific Microbial Whole-Cell Biosensor for the Detection of Histamine: A Potential Food Toxin

Histamine is a biogenic amine; its level indicates food quality, as elevated levels cause food poisoning. Therefore, monitoring food at each step during processing until it reaches the consumer is crucial, but current techniques are complicated and time-consuming. Here, we designed a Pseudomonas putida whole-cell biosensor using a histamine-responsive genetic element expressing a fluorescent protein in the presence of the cognate target. We improved the performance of the proposed biosensor by optimizing the chassis, genetic regulatory element, and reporter gene. A sensitive and rapid biosensor variant was obtained with a limit of detection (LOD) of 0.39 ppm, manifesting a linear response (R² = 0.98) from 0.28 to 18 ppm in 90 min. The biosensor showed minimal cross-reactivity with other biogenic amines and amino acids prevalent in food, making it highly specific. The biosensor effectively quantified histamine in spiked fish, prawn, and wine samples with a satisfactory recovery. Additionally, a colorimetric sensor variant P_AlacZ was developed enabling histamine quantification in seafood via a smartphone application, with an LOD_gray of 0.23 ppm, exhibiting a linear response from 0 to 2.24 ppm. Overall, this study reports an efficient, specific, and highly sensitive biosensor with strong potential for the on-site detection of histamine, ensuring food safety.