Antimicrobial Activity of Starch-based Biodegradable Antimicrobial Films Incorporated with Biosynthesized Silver Nanoparticles Against Multiple Drug-resistant Staphylococcus aureus Food Isolates

Abstract

This study was conducted to determine the antimicrobial activity of starch-based biodegradable antimicrobial films incorporated with biosynthesized silver nanoparticles (Ag-NPs) against multiple drug-resistant Staphylococcus aureus food isolates. Herein, the in-vitro antimicrobial activities of Origanum marjorana (OM) leaf extract, OM essential oil, OM nano-emulsion, chemically synthesized Ag-NPs (chem-Ag-NPs), and OM-based biosynthesized Ag-NPs (bio-Ag-NPs) using OM extracts were determined against a cocktail of three pathogenic Staphylococcus (S.) aureus strains isolated from meat products, using the agar well diffusion assay (AWDA). Afterward, homemade starch-based biodegradable antimicrobial films (SBAF) were incorporated with the suitable antimicrobials, based on AWDA and preliminary experiments, and investigated for their antimicrobial properties against S. aureus cocktail through the disc diffusion assay (DDA). The obtained results showed that in WDA, bio-Ag-NPs (1mM) had a significantly higher antimicrobial activity than chem-Ag-NPs (1mM), with inhibition zones accounting for 23 and 19mm, respectively. Whereas both types of nanoparticles were significantly more potent in their antimicrobial properties than different concentrations of OM extract, essential oil, and nano-emulsion (p<0.05). In concern to SBAF incorporated with antimicrobials, SBAF incorporated with chem-Ag-NPs (SBAF/chem-Ag-NPs) showed a significantly stronger antimicrobial effect than SBAF incorporated with bio-Ag-NPs (SBAF/bio-Ag-NPs) in the DDA, while both types of films produced significantly larger zones of inhibition than other antimicrobials (p<0.05). These homemade biodegradable films incorporated with bio-Ag-NPs could be a good alternative to petroleum-based packaging (plastic) in food packaging applications and meanwhile improve food safety and quality. Further studies investigating the effectiveness of these films on bacterial isolates inoculated in real food samples are suggested.