Nisin-Guar Gum Antimicrobial Hydrogel

Nisin stock solution (1,000 µg/mL) was prepared by dissolving 1 g of nisin powder (2.5% purity, 1,000 IU/mg, Sigma–Aldrich, St. Louis, MO, USA) in 25 mL of HCL (0.02M) (Merk, Darmstadt, Germany). Stock solution was filtered using a 0.22 µm cellulose acetate filter. Biogel at 1.5% (w/v) was prepared by dissolving 0.75 g of guar gum (Sigma–Aldrich, St. Louis, MO, USA) in 50 mL of sterile distilled water followed by heat sterilization by autoclave. Then, nisin solution was incorporated within the biogel, in a proportion of 1:1, to achieve a final nisin concentration of 200 µg/mL (Cunha et al., 2018 (link)).