Microbe Guide: Sporendonema casei

If you’ve ever spotted bright orange patches on the rind of a cheese, there’s a good chance it was Sporendonema casei. While orange may instill a sense a fear, this orange mold isn’t out to get you. It’s a benign mold species that contributes unique aesthetics and flavors in cheese rind ecosystems.

Sporendonema casei is one of two species in the fungal genus Sporendonema. The other species, Sporendonema purpurascens, is equally eccentric with it’s purple color and sometimes contaminates mushroom growing facilities.

Macro- and microscopic appearance:
The mycelium of this fungus is very slow-growing and is initially white (see photo below). As the fungus grows, it produces spores that create its orange color. In ideal conditions in the lab, this can take several weeks.

Orange patches are made up of mycelia that segment to form conidia (or spores) as shown below. This method of asexual reproduction is different from spore production in many other molds, such as Penicillium, which form spores on distinct structures called conidiophores.


Mycelium of Sporendonema casei growing in the lab (left). A microscopic view (400X magnificaiton) of the spores of this fungus (right).

Food habitat:
This mold is only found on the rinds of cheeses. According to recent work in France, it has never been found outside of the dairy environment. The fungus generally occurs after other fungi have colonized the cheese surface, although it has been observed growing on relatively young wheels of cheese. It is found on both European and North American natural rind cheeses.

Sporendonema casei growing on cheeses from Wisconsin (left), France (center), and the UK (right).

Sporendonema casei growing on cheeses from Wisconsin (left), France (center), and the UK (right).


It is important to note that Sporendonema casei does not cause the orange coloration of washed rind cheeses. Those cheeses get their orange colors from other bacteria, yeast, and molds.

Sporendonema casei, as with many naturally occurring cheese molds, has not been very well studied, so we know little about what it actually does to the cheese. Brian Ralph, the cave manager for Murray’s in New York City, has developed an aging technique where he inoculates Hudson Flower with Sporendonema casei. Brian notes that these cheeses have a deeper mushroom note compared to similar cheeses lacking the Sporendonema casei.

As far as we are aware, this fungus has never been reported to cause food-borne illness, infections, or produce mycotoxins, although there has not been a comprehensive assessment of the safety of this fungus.

Do you have interesting observations or questions about Sporendonema casei? If so, please leave a comment below to share with our web community.

There are 16 comments on this article

  • Lee Smith says:

    Unfortunately, in the United States, Sporendonema casei is often confused with red Pseudomonas. I see it much more often in Europe, especially on cave-aged sheep milk cheeses, where it is often an indicator of superior flavor. Typically, the cheeses seem to be more complex with exceptional nutty notes and balanced sweetness.

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    • Thanks for your observations, Lee! I agree that Sporendonema casei seems to be more abundant in Europe. In the US, I’ve noticed that it is especially abundant on natural rind cheeses in the Midwest. I don’t see a lot of it on the East or West Coasts. Does that align with your observations?

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  • Dan says:

    in France, Sporendonema casei is inoculated on Cantal cheese, Laguiole and Salers.
    The laboratory SAS LIP, in Aurillac is producer of this type of strains

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    • Bronwen Percival says:

      Hi Dan,
      I had the chance to visit LIP in Aurillac a few months ago and it was very interesting to see their approach to propagating and providing ripening microbes such as S casei to cheesemakers. It’s also possible to find this microbe occurring naturally on hard cheese rinds; we are seeing a lot of (uninoculated) Sporendonema on Berkswell at the moment. Thanks for your comment!

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  • Andrea says:

    just to tell that I had the occasin to isolate Sporendonema casei from the rind of a ewe’s cheese produced in Sardinia in the province of Cagliari – Italy; unfortunately the producer was not so happy about the bright orange colour. Greetings

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  • We’re happy to report that we have two cheese producers in whose cheeses we see the Sporendonema casei – Three Corner Field Farm and Bonnieview Farm. These are both sheep dairies – Three Corner Field is upstate NY and Bonnieview is in VT. Is there a higher instance of this mold occurring on the rinds of sheeps’ milk cheeses?

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  • Markus Femling says:

    Hello! I had my first encounter with Sporendonema a few weeks ago when i saw a most wonderful orange goat milk cheese from Jamtland in the north of Sweden. Apparently this mold is very common in the region. The cheesemaker is Skärvången and the cheese is called Källarlagrad Jämtländsk Vit Getost, which translates to “Cellaraged Jamtish White Goatcheese”. I will try to visit the cellars in a few months time.

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    • Hi Markus –

      Thanks for sharing your observations about Sporendonema! It is wonderful to hear about the molds people see in their journeys.


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  • Gwen says:

    Is this orange mold found only on the rind or does it grow throughout the cheese?I have half a wheel of cheese from Pennsylvania that just arrived with orange spots throughout.

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    • Hi Gwen –

      I’ve never observed Sporendonema casei growing within the paste of a cheese. If you have photos of this cheese, it would be great to send them along for us to see.

      Thanks for sharing your observations!


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  • Max says:

    Hi there,
    I have been to the Vanoise National park and spoke to a cheese maker at 2000m who showed me that when the “fleur rouge” appears on the cheeses it is a good sign of affinage. He took me outside with the cheese to show how what was growing on the cheese (which i had assumed was sporendonema) was also growing as a form of lichen all over the chalet and mountain. Please see the film I made about it here
    I would love to find out if someone knows if this is mould, or lichen, or both?!!?!?
    Max from London

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  • Paz Ardines lara says:

    Me gustaría saber si el Sporendonema puede comprarse para ponerlo en una cueva y la colonice a la vez que a unos quesos que maduran en ella, gracias

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  • Marcia B says:

    I was just looking at a photo from a new cheesemaker in South Australia (Lilyarra) ‘ Who’s making an Irish Style cheese – Càis Gabhar’ (Semi-hard Goat cheeses). He was rather excited to see Sporendonema casei, happily blooming on the rind.

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  • John says:

    I have a brie that has vegetable ash in the rind. The fungus mostly seems to grow on the cheese where the white rind is broken to expose the ash underneath

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  • Hello everyone!

    I am aging almost 2 tones of hard cheese which I made form the mixture of goats and sheeps milk which we collect from the Taurus Mountains at the south west coat of Turkey. I would love to share some pictures of the Sporendonema caseii growing on the surface our wheels. but I can not find a section to share photos.

    say cheese 🙂

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