Zinc-substituted myoglobin is a naturally occurring photoantimicrobial agent with potential applications in food decontamination

Zinc-substituted myoglobin (ZnMb) is a naturally-occurring photosensitizer that generates singlet oxygen with a high quantum yield. Using a combination of photophysical and fluorescence imaging techniques, we demonstrate the interaction of ZnMb with Gram positive Staphylococcus aureus and Gram negative Escherichia coli. An efficient antibacterial action against S. aureus was observed, with a reduction up to 99.9999% in the number of colony forming units, while no sizeable effect was detected against E. coli. Since ZnMb is known to form during the maturation of additive-free not-cooked cured ham, the use of this protein as built-in photodynamic agent may constitute a viable method for the decontamination of these food products from Gram-positive bacteria.