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Why is malt extract preferred over yeast extract/nutritional yeast for LC?


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#1 potatoman117

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Posted 15 June 2020 - 04:13 PM

I've read through many many published articles about mycelium. Everywhere from biomass, enzyme production, mycelium mass, colonization speed, density, sporulation ect.

The vast majority of articles including very recent ones mainly use 5g/1L-10g/1L of yeast extract or peptone. When malt extract is used it is usually in combination with yeast extract/peptone. (For pyslocibe cubesence)

Also many positive correlations with ratios of carbon and nitrogen (something like 10:1) with fruiting body size. Glucose (dextrose) is usually the best carbon source. I understand this is for different species of mycelium but the vast majority prefer yeast extract for a nitrogen source. At least %80-%90 preferred these as C/N sources.

I guess I'm still a little confused as to why malt extract is the standard when %90 of clinical trials use yeast extract?

I'm not saying LME is bad by any means I just don't know if I am missing something? Even adding 1-2g of yeast extract and 1-10g of peptone had pretty significant effects on quality of mycelium for pretty much every single paper I read. Including positive correlations for most of what I mentioned in the first paragraph.

Anyway if you know something I don't about LME please share :)

Btw malt makes a great LC (I've made about 20), I'm just asking why it is the standard and not brewers yeast/nutritional yeast or peptone isn't.

#2 PJammer24

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Posted 16 June 2020 - 08:48 AM

I've read through many many published articles about mycelium. Everywhere from biomass, enzyme production, mycelium mass, colonization speed, density, sporulation ect.

The vast majority of articles including very recent ones mainly use 5g/1L-10g/1L of yeast extract or peptone. When malt extract is used it is usually in combination with yeast extract/peptone. (For pyslocibe cubesence)

Also many positive correlations with ratios of carbon and nitrogen (something like 10:1) with fruiting body size. Glucose (dextrose) is usually the best carbon source. I understand this is for different species of mycelium but the vast majority prefer yeast extract for a nitrogen source. At least %80-%90 preferred these as C/N sources.

I guess I'm still a little confused as to why malt extract is the standard when %90 of clinical trials use yeast extract?

I'm not saying LME is bad by any means I just don't know if I am missing something? Even adding 1-2g of yeast extract and 1-10g of peptone had pretty significant effects on quality of mycelium for pretty much every single paper I read. Including positive correlations for most of what I mentioned in the first paragraph.

Anyway if you know something I don't about LME please share :)

Btw malt makes a great LC (I've made about 20), I'm just asking why it is the standard and not brewers yeast/nutritional yeast or peptone isn't.

Someone may be able to chime in on this and shine more light than I am able... I am sciencey but there are guys on here who have knowledge far beyond my own when it comes to the "why" of things... I have the "how" down pat and most of the "why" but if I am wrong on this, I am sure someone will correct me...

 

Malt is a source of sugars so the mycelium will have a food source... Yeast, a single cell organism, has its own metabolism and like the mycelium we are cultivating, it will colonize a food source... Yeast is a contaminate of mushroom cultures. Adding yeast to the mix adds a competitor that not only consumes resources intended for the mushroom mycelium but also would leave you with a mixed culture of both mushroom mycelium and yeast... Any time you use that LC to inoculate a jar, you are also introducing yeast... The same thing would happen from a culture plate when starting an LC... You would be introducing a competitor to your grows rather than the mushroom mycelium on its own...

 

To get to the nuts and bolts... Malt is a nutrient source.... Yeast is a competitor for that nutrient source.... The goal is to isolate healthy mushroom mycelium, not add an organism that will compete with it for resources.

 

I would have to read the papers suggesting that yeast can be beneficial, to me it seems counter intuitive to include it and would result in contamination issues... All you really need in an LC or culture of any type is a nutrient source... I will also use bacterial resistant agar mixes but its all really just a nutrient source for the myc to consume, I certainly have no plans of intentionally adding competition for the sugars in my LCs...

 

 

• Yeasts

Yeasts are another common contaminant that, just like fungi or bacteria, can ruin mushroom cultures. Oftentimes, a yeast contamination will appear anywhere in your jar as small spots that can be white or yellow. Other types of yeasts may appear like a bacterial contamination. Substrates are usually not contaminated by yeast, but it can be present in the spawn from where it will grow. Yeast can have various odours. 

https://www.zativo.c...m-contamination

 

 

 

Have I ever mentioned that it really chaps my bottom that spell check labels "mycelium" as being missed spelled on a mushroom cultivation forum? There are a couple other common mushroom terms that according to spell check, I am spelling wrong...


Edited by PJammer24, 16 June 2020 - 08:52 AM.





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