The Preparation Of Chitosan Particles Immobilized Nisin And The Antimicrobial Effect Of Immobilized Nisin

Nisin is a natural antimicrobial peptide produced by strains of Lactococcus lactis subsp.Lactis and it has received particular attention because of its large antibacterial activity against a wide variety of Gram-positive bacteria.Although Nisin has been used as the natural antiseptic substance,there is still a big weakness that the vulnerable degradation in fluids lead to shorten its shelf-life.In this study,in order to improve Nisin's stability and control its degradation,the immobilization of Nisin on chitosan nanoparticles and antibacterial property of immobilized Nisin were investigated.Chitosan nanoparticles with particle size(142.20±0.92)nm were prepared by the lab.The adsorption performance showed that the mode of adsorption to Nisin was multimolecular layer adsorption that was obtained as well as the optimum temperature 40 ?and the initial concentration of Nisin 3mg·mL-4.The effect factors of adsorption were investigated on this condition and then the optimum conditions were as fellows:adsorption time was 55min,shaking speed was 200rpm,the mass ratio of Nisin to Chitosan nanoparticles was 1.25(w/w),pH 4.0.The adsorption rate can achieve(90.50±4.26)%under the optimum conditions.Immobilized Nisin was prepared under the optimum condition,and then the antibacterial activity were investigated.The results showed that immobilized Nisin achieved better and longer bactericidal activity than free Nisin.Compared with the free Nisin,nearly 15%of the bactericidal rate was improved by the immobilized Nisin.In the fluid of the bacteria,the bactericidal time sustained for 8 days that increased 3-5 days.Under the condition of pH4,Immobilized Nisin showed bactericidal time at least more than twice as much as that of free Nisin in simulated liquid food at 25?.Immobilized Nisin and free Nisin sterilized by 121°C for 5 min and 10 min were investigated based on their bacteriostatic effect with inhibition zone method.The results indicated that immobilized Nisin showed better bacteriostatic effect than free Nisin.Form bacteriostatic effect of sustained release of immobilized Nisin in the buffer solution,increase of Nisin content from immobilized Nisin would increase sustained release time.Nisin concentrates as material were immobilized by chitosan nanoparticles.The results showed that immobilized Nisin also showed excellent antibacterial effect and sustained-release bacteriostatic effect.