Fractional Sterilization

Original article: http://forums.mycotopia.net/showthread.php?t=14500

Cultivating mushrooms in containers on a BRF substrate requires an effective sterilization process to be successful. In order to quickly grow a healthy BRF cake, mushroom mycelia must be the only (significant) fast growing life form in the container/jar. Sterilization of the substrate before spores are introduced is paramount to success. Any bacteria or other microbial life in the jar will compete with the mycelia and slow (or prevent) full colonization.

A Pressure Cooker can be used to sterilize BRF substrate . Pressure cookers are also bulky, reasonably expensive and very difficult to locate for some (you can't go pick up a cheap Pressure Cooker from the local big ‘Mart or thrift store in many other countries).

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The thrust of this document is a sterilization process called Fractional sterilization (hereafter FS). This process is also called tyndallization (as it was discovered by J. Tyndall in the mid 1800's). This is not a new idea/process. The tyndallization process predates home pressure cookers by over 100 years.
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The ideas that make FS/tyndallization work are very easy to understand:

1. Virtually all living contaminants are killed by boiling/steaming temperatures. If it is alive/growing, 60 minutes exposure to steam temperatures will kill it.
2. Most endospores (contaminant “seeds”) are NOT killed by boiling/steaming temperatures. Four hours of steam (at regular pressure) will not kill some very common bacterial endospores.
3. Given time and proper conditions to “hatch” and begin growing, even the toughest endospore becomes a (relatively) delicate living microbe which can be destroyed by steam heat at regular atmospheric pressure.
4. A process that germinates endospores and then destroys the resulting living contaminants can actually be more effective than pressure cooking (some endospores can survive 60 minutes @ 15psi in a pressure cooker).

BRF will contain some endospore contaminants that can not be killed by boiling/steaming. In order to destroy these threats, the high temperature stable endospores must be allowed to germinate (begin growing). Once germinated, the living contaminants are far more sensitive to boiling temperatures and can be destroyed straight away.
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Boiling/steaming temperatures can't kill endospores, but once they germinate/hatch, boiling/steaming temperatures can easily destroy the resulting microbial life.

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Please pardon the

Abstract: Use Fractional Sterilization/tyndallization to sterilize PF recipe BRF jars and Popcorn jars. inoculate half the jars with spores. Incubate all jars at 82F and observe for 10 days.

Test group (20 jars total – 10 BRF , 10 popcorn). Everything was done in ½ pint Ball-Mason jars using tyvek vented lids and silicone injection ports. All inoculations were done with spore water previously tested and known to be contaminant free. All inoculation work was done in front of a flow hood.

• 5 BRF jars, standard PF 2-1-1 recipe
  1. Jars prepared 8/31/06 and left to sit overnight
  2. 60 minutes steamed 9/1/06
  3. 60 minutes steamed 9/2/06
  4. 60 minutes steamed 9/3/06

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• 5 BRF jars, standard PF 2-1-1 recipe
  1. Jars prepared 8/31/06 and left to sit overnight
  2. 60 minutes steamed 9/1/06
  3. 60 minutes steamed 9/2/06
  4. 60 minutes steamed 9/3/06

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• 5 Popcorn jars, (2 with very little corn for Fahster clone jars)
  1. Popcorn hydrated, drained and put in a plastic bag for 24 hours
  2. 90 minutes steamed 9/2/06
  3. 90 minutes steamed 9/3/06
  4. 90 minutes steamed 9/4/06

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• 5 Popcorn jars, (2 with very little corn for Fahster clone jars)
  1. Popcorn hydrated, drained and put in a plastic bag for 24 hours
  2. 90 minutes steamed 9/2/06
  3. 90 minutes steamed 9/3/06
  4. 90 minutes steamed 9/4/06

<O</OThe steaming of jars was done in a large soup tureen. An inverted aluminum pie plate was used to raise the jars off the bottom of the pot, allowing more water to be added and decreasing the chances of cracking a jar. I took pictures of this setup, but since everything is shiny aluminum, the pics aren't really very much more enlightening than simple text.
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The steaming process went as follows:<O</O

1. The soup tureen was filled with water (with jars in it), to a point where the water was about ½ way up the sides of the jars.
2. Jars were removed and tureen put on the stove over high heat, until a rolling boil was developed.
3. Heat was reduced to about 1/2, jars were put in and pot was watched until water started to boil again (water was not reheated to a rolling boil).
4. As soon as water started to boil, heat was reduced to a level already known to produce only a gentle simmer. Jars were NOT done over a continuous violent/rolling boil, just a gentle simmer.
5. Lid was placed on pot and timing of the steaming cycle was begun.
6. At the end of the cycle jars were removed (with lifting tongs to avoid burns) and set aside to cool for 24 hours.
7. This exact process was repeated on all jars. The only process change was steaming the Popcorn jars for 90 minutes (instead of 60).

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So, what were the success rates like you may ask? In a word, they were GREAT! 100% sterilization across the board (even in the Popcorn , which was suprising).

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Group 1 was 5 BRF jars incubated for 10 days @ 82F without being inoculated. Success rate was 100% with no visible contamination at 10 days. At 10 days, these jars were inoculated and are growing out now.

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Group 2 was 5 BRF jars incubated for 10 days @ 82F with spore water inoculation . Success rate was 100% with no visible contamination at 10 days. These jars are very nearly finished.

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Group 3 was 5 Popcorn jars incubated for 10 days @ 82F without being inoculated. Success rate was 100% with no visible contamination at 10 days. These jars have been inoculated and are growing out.

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Group 4 was 5 Popcorn jars incubated 10 days @ 82F with spore water inoculation . Success rate was 100% with no visible contamination at 10 days. These jars have already been spawned to a bulk sub!

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To push the Popcorn test a bit farther, four of the Popcorn jars were prepared with only a small amount (perhaps 4 tablespoons) of Popcorn . After these jars were fully colonized, 60mL of sterile water was injected, the jars were shaken violently and 55mL-57mL of mycelia slurry was removed (this is Fahtster's Tek, not mine). Each syringe of slurry was used to inoculate the Popcorn layer of a Buckaroo Bulk nugget bag.

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All four Bucky Bags colonized their Popcorn layer cleanly! All four Fahtster clone jars recovered cleanly (and were used again – Fahtster's Tek is really great for making mycelia slurry syringes) ! ! !

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Not only was there no visible contamination in the Popcorn , there were no contaminants at all. Had there been any latent bugs, the speed of mycelia on Popcorn might have overtaken them without my notice.

By doing the Fahtster Tek, I am assured that things were clean inside the jar. All that sterile water would have washed any latent nasties off the corn and then deposited them for growth in the bulk nugget bag.
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So, not surprisingly, FS proved to be highly effective with BRF substrate .

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Somewhat surprisingly, FS proved to also be highly effective with popcorn.

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It takes a lot longer and it is a good bit more finicky, but FS/tyndallization can be used effectively by the home cultivator without access to a pressure cooker.
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for all you beginning myc heads

 

just look at it this way. you dont have to go out and buy a $200 pressure cooker/canner now! you got pans in your cubboard, you got your tek, you got your spores, and the best part is its almost guaranteed better than pressure cooking in certain situations!!! for the poor myc heads!!!! YA!!!