Adsorption of nisin on raw montmorillonite

• A series of food-grade montmorillonite nisin nanocomposite powders were obtained.
• Nisin interacted with the clay mineral by means of a “frustrated intercalation”.
• Antibacterial powders with nisin loading > 0.24 CEC fully inhibited E. faecium C1.
• Clay immobilization could protect nisin inhibitory activity in complex environments.

The aim of the present work was to develop food-grade materials capable of releasing antimicrobial agents. Montmorillonite (Mt), a raw, abundant inexpensive clay mineral approved as a food additive, was used as support material. The immobilized antimicrobial agent was pure nisin (Danisco, UK). A series of antibacterial compounds were prepared, and the antimicrobial activity of the resultant montmorillonite–nisin (MtNis) immobilized systems was determined against Enterococcus faecium C1. The characterization of the antimicrobial powders showed evidences of nisin adsorption on by means of a “frustrated intercalation” model with a nisin loading (NL) saturation value close to 0.24 CEC (cation exchange capacity) of Mt. The antibacterial powders with NL above this value completely inhibited E. faecium C1 during 24 h of contact. These results are encouraging for the development of nisin-based bioprotectors immobilized on raw Mt.

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