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

Abstract

The inhibitory effect of lactose oxidase on the growth of foodborne pathogens and spoilage microorganisms associated with dairy products was evaluated through an overlay inhibition assay. Lactose oxidase generates hydrogen peroxide via lactose oxidation into lactobionic acid. Escherichia coli O157:H7, Listeria monocytogenes, Salmonella enterica ser. Typhimurium, Staphylococcus aureus, Pseudomonas fragi, and Penicillium chrysogenum were used as indicators. A commercially available solution of lactose oxidase was applied at different concentrations (0, 0.12, 1.2, and 12 g/L) in 4 types of media [brain heart infusion agar (BHI), BHI + sodium thiocyanate (NaSCN), BHI + lactose, and BHI + NaSCN + lactose] to evaluate the effect of lactose and thiocyanate on microbial inhibition. Lactose oxidase inhibited the growth of all the indicators at a concentration of 12 g/L of the enzyme solution in the presence of lactose alone and in combination with NaSCN. However, supplementation with NaSCN had no effect on the magnitude of microbial inhibition. Staphylococcus aureus was the most sensitive pathogen, and Ps. fragi was the most sensitive of all the indicators in general to lactose oxidase. Listeria monocytogenes and Ps. fragi showed higher susceptibility to the antimicrobial effect of lactose oxidase at 6°C than at their corresponding optimum growth temperature. The inhibitory effect was attributed to the generation of hydrogen peroxide from the oxidation of lactose. Findings from this study demonstrate that lactose oxidase could be used as a novel approach to inhibit the growth of mold and bacteria. It could also be applied as a label-friendly preservative in dairy foods.

Comparison of Controlling Capabilities of Lactobionic acid, Nisin and K-Sorbate against Dairy-borne Staphylococcus aureus, Escherichia coli and mold in soft cheese

“…Therefore, although a pH drop is present in our study, there could be a potential to use LBA as an alternative preservative method in further studies to reduce spoilage in cheese as well as its application to reduce pathogenic growth. Previous research has indicated that extended exposure to LBA leads to notable decreases in pH in fluid milk, as demonstrated by Lara-Aguilar and Alcaine (2019 ). However, it is worth noting that the sensory impact may be less pronounced in low-pH dairy products, topical or spray applications, or scenarios where the LBA can be removed or inactivated.…”

Evaluation of Lactose Oxidase as an Enzyme-Based Antimicrobial for Control of L. monocytogenes in Fresh Cheese

“…In both of These results suggest that the production of H 2 O 2 by LO is sufficient to inhibit L. monocytogenes counts at different concentrations in queso fresco. A previous study [23] tested the effect of LO as an antimicrobial against L. monocytogenes using an overlay inhibition assay, and microbial inhibition was observed. Catalase was added to the treatments, and then, L. monocytogenes growth occurred, suggesting that a primary cause of bacteria inhibition was the production of H 2 O 2 by the LO reaction in solution.…”

“…LBA and H 2 O 2 have been shown to be effective inhibitors of L. monocytogenes in dairy products, demonstrating that the production of these antimicrobial agents by LO itself may be an effective strategy to control L. monocytogenes in cheese. In a previous inhibition assay study, LO combined with sodium thiocyanate (TCN) was shown to inhibit the growth of L. monocytogenes [ 23 ]. TCN combined with hydrogen peroxide has been shown to be an effective activator of the lactoperoxidase system, which is a natural antimicrobial system present in raw milk [ 24 , 25 ].…”

Effect of Temperature at the Shelf Life of Yogurt and the Role of <i>Listeria monocytogenes</i> and <i>E. coli</i> Inoculated in Unflavoured and Flavoured Yogurts

“…One of the main losses of food in dairy industry is the contamination by the pathogens. In 2010, more than 10 million tons of dairy product wasted due to these pathogens [14]. The incubation temperature of E. coli is 37°C while the incubation temperature of L. monocytogenes is 6 and 37°C.…”