A bacterium used to produce buttermilk has been given a new role by a research team in Cork. It is a powerful new weapon in the battle against the bacteria that cause food spoilage, the disease mastitis and even against the drug-resistant hospital "super bugs".
The organism produces a very effective bacteriocin, a substance that can kill off a wide range of bacteria. It can wipe out 95 per cent of the bacterial forms that cause mastitis and can extend the shelf life of a range of food products, keeping them safer for the consumer.
The work is by the Cork Bacteriocin Group, a co-operative venture between University College Cork and Teagasc's Moorepark research centre. The lactococcus bacterium was isolated from the extensive collection of lacto bacteria held at Moorepark, explained Dr Colin Hill of the Department of Microbiology at UCC.
"Every now and then we go in and mine that collection to see what we can find," he explained. They search on the basis of particular characteristics or attributes that can be applied in the general area of food science.
Dr Hill will be presenting some of the work done by the group at EuroLAB, a conference taking place at UCC from July 3rd-6th. It brings together researchers from all over Europe who work with lactic acid bacteria used in food fermentation and other food processing technologies.
These bacteria are central to many of the foods we eat, Dr Hill said, including yoghurt, processed meats and cheeses. "The main way they preserve foods is by acidification," he said, but some lactobacteria also produce bacteriocins. "They are very small peptides produced by the bacteria to kill other bacteria."
These peptides form a key defence in the "bacteria wars", the invisible battles that take place as one bacterium attempts to wrest control over a food source. Dr Hill joined Dr Paul Roos of Moorepark in a search that saw literally thousands of bacteria cultures studied for new bacteriocins.
They found what they were looking for in what is known as a "buttermilk plant", something that has nothing to do with vegetation. A buttermilk plant is a "complicated community" of different bacteria and sometimes yeasts that join together and coexist. They form a physical structure around themselves that looks something like a piece of cauliflower, hence the name.
The plant colony will convert fresh milk into buttermilk and buttermilk plants can be passed down through generations, Dr Hill said. They are still in widespread use in eastern Europe.
The group's new bacteriocin has been named Lacticin 3147. It involves a small chain of 30 to 40 amino acids, but it is a powerful agent against gram positive bacteria, punching holes in the cell wall to kill off the bug. "It is extremely active at low concentrations," Dr Hill said, and remains stable and effective even after the heat of processing and cooking.
The agent has a wide range of uses, Dr Hill said. "What we have been trying to do is explore as many applications as we could imagine." It is readily broken down in the stomach so it poses no threat if eaten but it plays havoc with competing bacteria.
It could be used in fermented foods where its bacteriocin will keep spoilage bacteria at bay, extending shelf life and safety, he said. If used to inoculate fresh milk destined for drying as milk powder, the lacticin remains active, continuing to protect the powder against bacterial attack.
"The mastitis angle is a very unusual one," Dr Hill said. Mr Billy Meaney of Moorepark, one of Ireland's leading mastitis research ers, had developed an anti-mastitis cream called a "teat seal" which provides a physical barrier against mastitis bacteria. Antibiotics have in the past been a mainstay in mastitis control and could be added to the seal "but the use of antibiotics is not being promoted very much any more", Dr Hill explained.
Instead the research group tried using lacticin with the teat seal and got much-improved results. In tests where researchers actively sought to cause infection, the teat seals proved 50 per cent effective but the seal with lacticin was 90 per cent effective, Dr Hill said.
One disadvantage of this versatile bacteriocin is that it is ineffective against gram negative bacteria, the rogues of food-borne bugs that includes E.coli, campy lobacter and salmonella. It destroys most gram positive bacteria, however, including the dreaded multi-drug resistant bacteria found in hospitals that can survive most antibiotics.