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From soil to cheese: What is Penicillium roqueforti's amazing journey like?
Cheese often plays an important role in our daily diet, but few people know that there are amazing stories of microorganisms behind these delicious blue cheeses. Penicillium roqueforti, a ubiquitous fungus, makes a surprising journey from soil to cheese.
Classification and history of Penicillium roqueforti
Penicillium roqueforti is a common saprophytic fungus first described in 1906 by American mycologist Charles Thom. This fungus was originally classified as a heterogeneous species, divided into species based on their phenotypic differences. Later, with the development of molecular techniques, these fungi were reclassified as the same species by Kenneth K. Raper and Tom in 1949. In 1996, based on the analysis of ribosomal DNA sequences, this classification was adjusted again, and Penicillium roqueforti was reclassified into three different species:
"P. roqueforti, P. carneum, and P. paneum."
Biological characteristics and environmental adaptability
The appearance of Penicillium roqueforti is less noticeable. This fungus does not form visible fruit bodies, but relies on the macroscopic morphology of its colonies growing on different standard agar media. When it is grown in Czapek yeast self-solution agar or yeast extract sucrose agar, it means that the colony diameter is about 40 mm, and the surface is usually olive brown to dark green. These characteristics allow it to survive and thrive in a dairy environment.
Main use: production of blue cheese
The main industrial use of Penicillium roqueforti is in the production of blue cheese, such as the French Roqueforti to which its name refers. Additionally, it is used in other famous blue cheeses such as Stilton, Danish Blue, and Combezzola. The flavor of these cheeses comes from the active presence of P. roqueforti in cream, which when mixed with air creates a richly flavored blue cheese dressing.
Effects of secondary metabolites
Although Penicillium roqueforti is important in cheese production, some of its secondary metabolites may also have deleterious effects under certain growing conditions. Research shows that most strains produce harmful secondary metabolites such as alkaline-like substances and other mycotoxins.
"Aristolochene is a sesquiterpenoid produced by P. roqueforti and may be the precursor of PR toxin."
The toxin has been implicated in poisonings caused by eating contaminated grains, but the PR toxin is unstable in cheese and eventually breaks down into the relatively less toxic PR imine.
Diverse environmental adaptability
The fungus can tolerate low temperatures, low oxygen, and slightly acidic and alkaline environments, allowing it to survive in a variety of environments, especially dairy products. On the other hand, it can also cause spoilage of refrigerated foods and meat, bread and silage feed.
Penicillium roqueforti strains from different sources show significant genetic diversity, which may give them an advantage in a highly competitive environment.
Smell and other applications
Penicillium roqueforti is not limited to cheese, its microbial strains are also used to produce other antibiotics, flavors and spices. These uses do not require special regulations under the U.S. Toxic Substances Control Act. The resulting texture is chitinous, increasing its potential for widespread industrial applications.
Summary: The future of microorganisms
The story of Penicillium roqueforti reveals the profound impact microorganisms have on our daily lives. From soil to cheese, this tiny fungus not only changes the flavor of food, but may also affect our health and the environment. As our understanding of these microorganisms increases, can we expect better utilization and management of them in the future?
