New strategy identified to fight bacterial cheese contamination

Friday 27 August 2010

Scientists have identified a way of using a virus to control levels of the Clostridium tyrobutyricum bacteria in cheese to prevent spoilage and minimise product waste.

Originating from the silage that cows eat, C. tyrobutyricum is a significant problem for cheese makers, especially manufacturers of hard or semi-hard cheeses. Even small amounts can produce butyric acid, which gives off a rancid taste, and result in an excess build-up of carbon dioxide causing cracks to emerge.

Writing in the journal Applied and Environmental Microbiology, scientists from the Institute for Food Research (IFR) claim to have identified and characterised a microorganism that specifically attacks the contaminant.

They concentrated their work on a bacteriophage (a type of virus that infects bacteria) called ΦCTP1. This produces a protein, called an endolysin, which recognises C. tyrobutyricum and breaks open its cells from the inside.

By sequencing the genome of endolysin, identifying the gene encoding it and then expressing this gene in E. coli, IFR research leader Arjan Narbad told that the team was able to produce endolysin and introduce it to break down C. tyrobutyricum from the outside.

Highly specific
In laboratory trials and in milk, Narbad said endolysin proved to be effective in reducing levels of C. tyrobutyricum and importantly their research suggests that it is highly specific. This means that using endolysin to control the bacteria may not interfere with the bacteria that ferment the cheese.

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