Short communication: Screening inhibition of dairy-relevant pathogens and spoilage microorganisms by lactose oxidase

摘要

The inhibitory effect of lactose oxidase on the growthof foodborne pathogens and spoilage microorganismsassociated with dairy products was evaluated throughan overlay inhibition assay. Lactose oxidase generateshydrogen peroxide via lactose oxidation into lactobionicacid. Escherichia coli O157:H7, Listeria monocytogenes,Salmonella enterica ser. Typhimurium, Staphylococcusaureus, Pseudomonas fragi, and Penicillium chrysogenumwere used as indicators. A commercially availablesolution of lactose oxidase was applied at differentconcentrations (0, 0.12, 1.2, and 12 g/L) in 4 typesof media [brain heart infusion agar (BHI), BHI + sodiumthiocyanate (NaSCN), BHI + lactose, and BHI +NaSCN + lactose] to evaluate the effect of lactose andthiocyanate on microbial inhibition. Lactose oxidaseinhibited the growth of all the indicators at a concentrationof 12 g/L of the enzyme solution in the presenceof lactose alone and in combination with NaSCN. However,supplementation with NaSCN had no effect onthe magnitude of microbial inhibition. Staphylococcusaureus was the most sensitive pathogen, and Ps. fragiwas the most sensitive of all the indicators in generalto lactose oxidase. Listeria monocytogenes and Ps. fragishowed higher susceptibility to the antimicrobial effectof lactose oxidase at 6°C than at their correspondingoptimum growth temperature. The inhibitory effectwas attributed to the generation of hydrogen peroxidefrom the oxidation of lactose. Findings from thisstudy demonstrate that lactose oxidase could be usedas a novel approach to inhibit the growth of mold andbacteria. It could also be applied as a label-friendlypreservative in dairy foods.