Preventing Spoilage in Cheese

NORWICH, United KindgdomBacteria, specifically Clostridium tyrobutyricum bacteria, are found naturally in soil, silage, hay and milk and contribute to contamination during the cheese-making process. Even small amounts of the bacteria alter fermentation, causing an excess build-up of CO2 and the production of butyric acid, which gives a rancid taste. Such spoilage has been difficult to control, as the spores of the bacteria are heat-resistant and can survive pasteurization.
Researchers at the Institute of Food Research identified and characterized a naturally occurring microorganism that specifically attacks C. tyrobutyricum: Bacteriophages. Bacteriophages are viruses that infect bacteria, and their use to control food spoilage bacteria.

In research published in Applied and Environmental Microbiology, the researchers demonstrated the potential use of this bacteriophage for controlling C. tyrobutyricum. The bacteriophage produces a protein, called an endolysin, which recognizes C. tyrobutyricum and breaks open its cells. The researchers sequenced the genome of the bacteriophage and identified the gene encoding the endolysin. By cloning this gene into E. coli, they were able to produce the endolysin protein to assess its ability to control C. tyrobutyricum levels.
The endolysin effectively reduced levels of C. tyrobutyricum in laboratory trials on cheese, as well as in milk. The endolysin showed strong specificity for C. tyrobutyricum, and did not interfere with the bacteria that ferment cheese.