Antimicrobial peptides made by Propionibacterium species, candidates for gentle, label-friendly preservation. The best studied, propionicin PLG-1 from P. thoenii strain P127, kills target cells rather than merely inhibiting them and works against many Gram-positive and Gram-negative bacteria plus certain yeasts and molds. Heat destroys its activity, which limits applications to unheated or mildly processed foods. Research continues into purification, spectrum, and regulatory status, but the concept fits the industry’s search for natural alternatives to synthetic preservatives. Toxicity testing and regulatory approval precede any commercial use in foods.