Formulation, Characterization and Assessment of the Inhibitory Effect of Microencapsulated Microcin J25(G12Y)

This study aimed to evaluate the physicochemical properties and antimicrobial efficacy of the encapsulated microcin J25 variant G12Y [MccJ25(G12Y)] using brea gum (BG) as a carrier matrix via spray-drying. The encapsulation process yielded 67% (w/w), producing a fine, homogeneous, non-agglomerated powder with a Sauter mean diameter of 12.2 ± 0.5 μm, high encapsulation efficiency, and stability for at least 120 days at 4 °C or 25 °C. The powder exhibited low moisture content (7.55 ± 0.17%) and water activity (0.27 ± 0.03), ensuring physical stability. Sorption isotherms indicated pronounced moisture uptake above 0.55 aw, consistent with the hydrophilic nature of the matrix. GAB modeling outperformed BET (R² > 0.90), supporting a thermodynamically favorable and exothermic water-sorption process. The identity and purity of the purified MccJ25(G12Y) peptide were confirmed using MALDI-TOF mass spectrometry. A monoisotopic mass of 2212 Da was experimentally determined for the first time, in full agreement with the theoretical mass increase expected from the glycine-to-tyrosine substitution at position 12 of the parental MccJ25. In vitro antimicrobial assays against foodborne Gram-negative pathogens, including Salmonella, Escherichia, Shigella, and Enterobacter spp., showed effective concentrations ranging from 0.6 to 9.4 mg/mL. Efficacy was further confirmed in a ground beef model, where the treatment with 4 mg/g of the powder reduced Escherichia coli O157 (NCTC 12900) viability by approximately 4 log CFU/g in 72 h. Encapsulated MccJ25(G12Y) in brea gum presents a promising strategy for food biopreservation, offering a stable powder with extended antimicrobial functionality and demonstrated effectiveness in food systems.