Enterococcal phages as biotechnological tools towards the reduction of biogenic amine accumulation in dairy products

Abstract

Biogenic amines (BA) are nitrogenous compounds with important biological activities. However, due to the metabolism of certain bacteria, BA can accumulate in high concentrations in food and its consumption constitutes a toxicological threat. Cheese is one of the foods that higher concentrations of BA can accumulate, being lactic acid bacteria (LAB) the main BA-producers. Consequently, most of the methods proposed for reducing BA in food, which are based on reducing the presence of BA-producing bacteria, have not only failed to completely solve the problem, they also affect non-BA producing LAB that are essential in the development of the organoleptic characteristics of cheese. Therefore, new and more specific solutions are needed. Bacteriophages have arisen, in recent years, as a promising antimicrobial weapon both in clinical and food safety applications. They present some properties that made them ideal biotechnological tools against food spoilage microorganisms such as BA-producing bacteria: they are extremely host-specific, are food-grade, have a long shelf life, are able to resist the environmental stresses encountered during food processing, are relatively cheap and easy to isolate and propagate, and since they are self-replicating and self-limiting, low dosages can be employed since they multiply only, and as long as the host is present. In this communication, we present the isolation and further characterization of dairy phages against Enterococcus faecalis, species mainly responsible of the accumulation of tyramine and putrescine in cheese. Among them, we have chosen phage Q69 for an in deep characterization and to perform a proof-of-concept challenge to reduce the presence of tyramine in a cheese experimental model. The addition of Q69 reduced the concentration of tyramine below its toxic threshold limit.