Sargassum -Derived Gold Nanoparticles for Biofilm Control: Innovative Sustainable Paint Coatings for Dairy Contact Surfaces

Biofilm formation on food contact surfaces is a significant threat to food safety in the dairy industry. This study presents an eco-friendly approach using gold nanoparticles synthesized from Sargassum sp. (S-AuNPs) to mitigate biofilms on SS-316 stainless steel and glass surfaces. Biofilm-forming bacteria, mainly Klebsiella and Enterobacter species, were isolated from dairy waste and confirmed via 16S rRNA sequencing; over 73% of strains showed high resistance to common antibiotics, highlighting the need for alternative solutions. S-AuNPs were thoroughly characterized by UV−vis, FTIR, SEM, EDAX, and XRD, revealing an average particle size of 48.7 nm and strong colloidal stability. Antioxidant assays demonstrated up to 49% radical scavenging activity at 100 μg/mL. Antibacterial tests showed inhibition zones ranging from 8 to 20 mm against resistant biofilm isolates, and synergy with methicillin increased inhibition zones further. Coating studies on SS-316 and glass coupons demonstrated up to 2.2 log reduction in biofilm biomass (from 6.48 to 4.27 log CFU/mL in Klebsiella and similar trends for Enterobacter ), with resin/S-AuNP and Apcomin/S-AuNP coatings offering the most effective biocidal performance. These results underscore the potential of Sargassum -derived gold nanoparticles as sustainable and effective biocidal coatings for dairy processing equipment, providing a viable alternative to traditional chemical sanitizers.