Efficacy of microencapsulated nisin with sodium alginate and chitosan on biofilm formation in Listeria monocytogenes

Listeria monocytogenes is a foodborne pathogen the cause of listeriosis that has long-term survival due to biofilm formation. This study aimed to investigate the efficacy of nisin 102 IU/ml, nisin encapsulated with chitosan and sodium alginate on biofilm formation and changing the expression level of genes related to biofilm formation in L. monocytogenes. L. monocytogenes ATCC 19115 (serotype 4b) was treated by nisin 102 IU/ml and microencapsulated nisin with chitosan and sodium alginate solutions. The effectiveness of nisin on cell survival was estimated by calculating the optical absorbance. After proving the presence of prfA, sigB, and agrA genes, the effect of 102 IU/ml nisin dilution on L. monocytogenes biofilm was investigated by the microtiter plate method. The expression level of prfA, sigB, and agrA genes was analyzed using real-time PCR methods (qRT-PCR). The inhibition rate of biofilm formation in L. monocytogenes by nisin 102 IU/ml was 57% at 37°C and pH 5.5. The maximum inhibition of biofilm formation was related to the simultaneous use of nisin 102 IU/ml with chitosan and sodium alginate at 37°C and pH 5.5. Nisin microencapsulated with chitosan and sodium alginate can increase its effectiveness in preventing the biofilm formation of L. monocytogenes to 76% (p<0.0001). Nisin 102 IU/ml decreased the expression level of prfA, sigB, and agrA by -2.313, -2.808, and -1.453-fold compared to the control (p<0.0001). Nisin only had significant inhibitory activity against L. monocytogenes biofilm. Nisin microencapsulated with chitosan and sodium alginate had high efficacy in preventing the biofilm formation of L. monocytogenes.