A Whole-Cell System Based on Engineered Bacteria to Assess Cobalt Presence in Food: The Example of the Pasta Production Chain

With the aim of developing a new tool to meet the increasing demand for food safety, a whole-cell-based system able to detect the presence of cobalt contamination along the pasta production chain was constructed. This system is based on bacterial cells engineered with a plasmid containing the eGFP gene under the control of a promoter sequence, and is able to elicit a fluorescence signal when activated. The promoters of four stress-responsive genes (DnaK, GroE, UspA, and ZntA) were used to test their responsiveness to cobalt; the promoter of the UspA gene, coding for a universal stress protein, was chosen. The UspA promoter was activated by cobalt, and the system described was highly sensitive, successfully detecting low concentrations of cobalt within complex food matrices derived from durum wheat seeds when exogenous cobalt was added. In food matrices tested alone, a fluorescence signal was present only in bran and fine bran, confirming that these parts of the wheat seed are the ones in which contaminants accumulate. Conversely, in the other matrices derived from the inner part of grains, no signal was detected. The findings reported contribute to the development a new, effective and sensitive tool for monitoring cobalt contamination, offering a valuable approach to enhance food safety control.