Some microbes can reduce allergic reactions in many people – ScienceDaily

The solution to mitigate the unpleasant reactions resulting from the consumption of ripened cheeses could lie in the bacteria that populate the cheese crust, said Stephan Schmitz-Esser, badociate professor of zootechnics. Schmitz-Esser led a new study, published in the peer-reviewed academic journal on Tuesday Scientific reports, which closely examines the microbial communities that develop in cheese crusts, and research could pave the way for better cheese production techniques to reduce the compound responsible for these reactions.

Many varieties of hard cheeses, such as Comte and Gruyère, need several months of ripening to obtain the desired flavor and aroma. When the cheese matures, a biofilm of bacteria and fungi develops on the surface of the cheese. These microbial communities, which naturally form and are not inoculated by cheese producers, play a critical role in the ripening process and can protect the cheese against harmful pathogens, Schmitz-Esser said.

"We still know very little about these microbial communities that are growing on the skin of cheese," he said. "We know they work, but we do not know much more."

These microbes produce histamine, a compound involved in local immune responses, as a byproduct of fermentation, he said. Foods rich in histamine can cause rashes and other symptoms badociated with allergic reactions in approximately 1% of humans.

Schmitz-Esser and his collaborators decided to answer some of the cheese producers' questions about these microbes. The researchers sampled cheese crusts originating in Austria and isolated the strains of bacteria that they contain. They identified a particular bacterial genus, called Brevibacterium, and sequenced the genomes of three different species. These data allowed them to identify pathways in bacterial genomes likely to regulate histamine degradation. Finally, the researchers developed the bacterium in an experimental setting and demonstrated their ability to break down histamine.

Schmitz-Esser said that all the Brevibacterium strains that the team studied did not possess the genetic pathway that most likely reduces the histamine content, but that it might be possible to exploit strains that express this pathway in the maturation process.

"In the end, this could allow us to intentionally use such strains capable of breaking down histamine," he said. "These bacteria would promote the maturation process while reducing the production of histamine."

The research could allow diners sensitive to histamine reactions to taste refined cheese, and could also help cheese producers to normalize the ripening process and improve their effectiveness, said Schmitz-Esser. The maturation time of the cheese represents a major investment by the producers. Optimizing the process guarantees producers the best return on investment, he said.

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