A combined treatment of Proteinase K and biosynthesized ZnO-NPs for eradication of dairy biofilm of sporeformers.

Biofilms of sporeformers found in the dairy industry are the major contaminants during processing, as they withstand heat and chemical treatment that are used to control microbes. The present work is aimed to remove these resistant forms of bacterial community (biofilm) present in dairy production lines using ecofriendly agents based on proteinase K (Prot-K) coupled with Zinc oxide nanoparticles (ZnO-NPs). Some metal/metal oxide (Ag, CuO and ZnO) NPs were prepared microbially, and ZnO-NPs were characterized as the most effective ones among them. The produced ZnO-NPs were 15-25 nm in size with spherical shape, and FTIR analysis confirmed the presence of proteins and alkanes surrounding particles as capping agents. Application of Prot-K for eradication (removal) of a model biofilm of mixed sporeformers on food-grade stainless steel resulted in an 83% reduction in the absorbance of crystal violet-stained biofilm. When Prot-K was mixed with the biosynthesized NPs ZnO_G240, the reduction increased to 99.19%. This finding could contribute to an efficient cleaning approach combined with CIP to remove the recalcitrant biofilms in dairy production lines.