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Mycotopia Web Archive Archive Liquid Culture: Karo/Honey/Dextrose Q&A series of dilutions of potato dextrose broth Previous Next

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Hippie3 (Admin)
Posted on Thursday, November 14, 2002 - 02:26 am:Edit Post Quote Text Delete Post Print Post Move Post (Moderator/Admin Only)

sez workman


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The impurities are likely adding to your success with pure sugar solutions. Mycelium needs trace elements and a nitrogen source to thrive, which are sorely lacking in carbon rich sugar solutions. I am suprised that there are any successes using pure dextrose or even relatively pure corn syrup. Also the sugar to water ratios are a bit high and can cause osmotic stress to the mycelium cells which will slow growth.

A few years ago I tested a series of dilutions of potato dextrose broth to see what the dilution was for best growth. I started with the below stock solution.

Stock solution (100%)
250ml potato water from boiled potatoes
1 tsp dextrose powder from the brew store

I then did rough serial dilutions of 50%, 25%, 12% and 6% as shown in the image. The blue things are magnetic stir bars. The jars are illuminated from the bottom to show detail.


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Suprisingly the 25% dilution was the thickest and fastest growing, but even the minimal dilution of 6% had good growth. More than enough to be used for innoculation purposes. It might even be better since the thinner mycelium is easier to draw up into a syringe without clogging and doesn't form the thick mat on the surface. The 25% eventually formed mushrooms on the floating mycelial mat, but I didn't take a picture

Currently I use a teaspoon of malt per 500 ml of water in a quart jar. Its a bit thick when colonized (like jello) but its an easy measure and it works fine for my purposes. Malt, like potato water is unrefined and contains all necessary elements for healthy fungal growth. It is no accident that you don't see recipes for honey water, dextrose or karo agars.

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