Synthesis and characterisation of alternan-stabilised silver nanoparticles and determination of their antibacterial and antifungal activities against foodborne pathogens and fungi

Abstract In this study, alternan isolated from Lactobacillus reuteri E81 was used as the stabilising agent to produce alternan-stabilised silver nanoparticles (AgNPs-Alt) and AgNPs-Alt were characterized and their antibacterial and antifungal activities were tested. The formation and the stability of AgNPs-Alt were determined by UV–vis spectroscopy analysis. SEM and TEM analysis revealed the uniform morphology of AgNPs-Alt with an average size of ~50 nm. The crystalline nature of the AgNPs-Alt was confirmed by XRD analysis. The interactions of alternan functional groups with silver was observed by FTIR analysis and thermal characteristics of AgNPs-Alt were determined by DSC analysis. Finally, the antibacterial and the antifungal activities of AgNPs-Alt were tested and AgNPs-Alt revealed inhibitory effects to pathogenic strains at 0.25 mg ml−1 concentration and this activity was observed to be concentration dependent. For the antifungal activity, a higher level of AgNPs-Alt was required compared to the antibacterial activity.