Evaluation of the Antimicrobial Efficacy of Nisin-Loaded Particles with Different Surface Charges

Nisin is a well-known bacteriocin used for food preservation. Encapsulation technologies can help increase its stability and protect its interaction with food components. The surface charge of nisin-loaded particles usually depends on that of the carrier. However, the effect of the positive and negative charge of the particles on the expression of antimicrobial activity is not fully understood. This study aims to determine how the surface charge of nisin-loaded particles influences their antimicrobial activity against Staphylococcus aureus and Streptococcus pyogenes. Nisin-loaded particles were fabricated using three types of pectin, such as high methoxyl, low methoxyl pectin, and pectic acid, at the final concentrations of pectin and nisin of 0.2 mg/mL and 0.1 mg/mL, respectively, followed by coating with chitooligosaccharides at 0.025 mg/mL and 0.3 mg/mL. Nisin release from particles was analysed at pH values 2, 6, and 8. The Korsmeyer-Peppas model provided the best description of nisin release. The antibacterial effect of nisin-loaded low methoxyl pectin particles, uncoated and coated with chitooligosaccharides, was investigated on Gram-positive bacterial strains S. pyogenes ATCC 12384 and S. aureus ATCC 25932. The zeta-potentials of nisin-loaded particles uncoated and coated with 0.025 mg/mL of chitooligosaccharides were - 20.6 ± 5.8 and - 18.1 ± 0.7 mV, respectively. The particles coated with 0.3 mg/mL of chitooligosaccharides were positively charged, with a zeta potential of 20.0 ± 5.0 mV. The study showed that there was no significant difference (p > 0.05) in the antibacterial effect of particles with the same but opposite charge, that is, negative and positive. This finding broadens the possibilities for nisin formulations and the design of new delivery systems.