Natural microbe inhibitor is found by scientists in Cork

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Observing the ability of antibiotics to suppress the growth of troublesome microbes on a petri dish is an awe-inspiring sight for scientists.

Seeing Lacticin 3147, a tiny protein made up of just two peptide units, display its inhibitory powers evokes the same sense of excitement. Its remarkable abilities have been identified by a team at Teagasc's Dairy Products Research Centre at Moorepark, Co Cork, and UCC.

What's more, it is a natural inhibitor which can be easily introduced into dairy products, according to Dr Paul Ross, head of Moorepark's dairy quality department. This is a new approach to suppressing the growth of pathogenic organisms.

"We see it as having potential as an alternative to chemical preservatives in food, and in some instances as a natural alternative to antibiotics, at least in veterinary use," he said.

This stems from the discovery of a natural inhibitory agent secreted by a lactic acid culture. It is a collection of microbes which generate lactic acid and play a key role in the manufacture of some dairy products. They are called "starter cultures" as they trigger fermentation in cheese or yoghurt-making. The key organism involved is Lactococcus lactis.

Lacticin 3147, which kills "gram-postive" microbes by forming pores in their cell membrane, was found when the team went in search of bacteriocins, natural chemicals capable of suppressing microbes, and screened "buttermilk plants" used domestically to sour milk for bread-making.

It is effective against a range of problem organisms, including the notorious food pathogens Listeria monocytogenes and Clostridium botulinum, though it does not kill all microbes in such foods. It is particularly effective in cheeses.

"We can naturally transfer the ability to make Lacticin to dairy starter cultures. We now have a range of starters that produce it." Thus starters double up as protective cultures in the making of cheddar cheese, cottage cheese and surface-ripened cheeses.

Through work with Dr Colin Hill of UCC, a range of applications in dairy foods and beyond are being investigated. Already, it has been found that the lacticin-producing organism, commonly used in cheese manufacture, successfully prevents listeria bacteria growing in soft cheeses.

This allows an extra layer of protection in ensuring their safety, Dr Ross explained. It also plays a role in accelerating ripening of hard/semi-hard cheeses. It is a tool to control what grows in cheese, particularly its flora. It suppresses the growth of troublesome spoilage organisms, allowing the use of a higher ripening temperature and accelerated flavour development.

A dry whey-based powder enriched for Lacticin has also been produced, which could be used as a preservative in a variety of foods, especially tinned products.

The versatility of Lacticin 3147 is shown in its ability to suppress organisms causing mastitis in dairy cows. This application is the subject of a licence with an Irish veterinary products manufacturer, Cross Vetpharm, which has incorporated it into teat-seals in collaboration with Mr Billy Meaney at Moorepark.

It is combined with teat seal product and injected into the cow teat during drying off and it has successfully passed animal trials at Moorepark.

The Lacticin provides extra anti-microbial protection in addition to the physical barrier, and could lead to a reduction in prophylactic use of antibiotics in the control of this most persistent disease in dairy cows.

The possibilities of Lacticin working against human pathogens, particularly against bacteria resistant to drugs, is being examined - there are no indications of resistance to Lacticin building up, in the laboratory at least.

The Teagasc-UCC team has made a further progress by identifying, using gene-sequencing, the genetic determinants which encode and control the generation of the inhibitor. The potential applications of a substance with such diverse uses are patented and attracting international commercial interest.

The quality of their research shows Irish food scientists leading the move to greater use of natural components in food production. They are also opening up new possibilities in the preventative approach to disease in animals, if not yet humans.

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