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Paper on microwave sterilization


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#1 CatsAndBats

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Posted 05 August 2016 - 05:50 AM

So I found this paper on microwave sterilization, I chose to put it here because I am about to 'live' in mad scientists and will be testing all sorts of edgy methods. The paper is a reference and it was one of the more user friendly/easy reads that I found. Drink a cup of coffee to stay awake while reading. Page three is where it gets interesting. :tongue:

 

Summary:

 

The Effects of Microwave Radiation on Microbial Cultures Slobodan M. Janković, Milorad Z. Milošev, Milan LJ. Novaković Faculty of Medical Sciences, University of Kragujevac, Kragujevac, Serbia

 

SUMMARY Microwaves are non-ionizing electromagnetic waves with frequencies between 0.3 and 300 GHz. Both humans and microorganisms living on the human body are exposed to significant doses of microwave radiation in everyday life. Whether and how microwave radiation could influence the viability and growth of microorganisms is the subject of this educational paper.

 

Download of entire paper:

Attached File  microwaveSterile.pdf   128.12KB   81 downloads


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#2 PsyBearknot

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Posted 06 August 2016 - 09:45 PM

Nice find I'd like to read it one f these days!

#3 ShadyWays

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Posted 12 August 2016 - 10:58 AM

So I guess it stands to reason that you'd have to nuke the jars or substrate separate from the items used for housing the substrate.  For example, if using jars the metal lids would need to be sterilized independently.  I think vermiculite contains aluminum and iron minerals, which could produce some interesting outcomes.

 

There's definitely an attraction related to speeding up the sterilization process, though.  I can't wait to hear more!


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#4 CatsAndBats

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Posted 12 August 2016 - 11:10 AM

So I guess it stands to reason that you'd have to nuke the jars or substrate separate from the items used for housing the substrate.  For example, if using jars the metal lids would need to be sterilized independently.  I think vermiculite contains aluminum and iron minerals, which could produce some interesting outcomes.

 

There's definitely an attraction related to speeding up the sterilization process, though.  I can't wait to hear more!

I've sterilized vermiculite in the microwave tons of times, with no ill effects.


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#5 hyphaenation

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Posted 12 August 2016 - 11:28 AM

Sterlized without pressure?

#6 CatsAndBats

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Posted 12 August 2016 - 12:07 PM

There are methods of sterilization that do not involve pressure. Irradiation, UV light, chemical, etc.. 

 

Microwave sterilization:

 

http://jcm.asm.org/c...t/6/4/340.short

 

http://onlinelibrary...04.02406.x/full

 

Chemical:

 

http://www.ncbi.nlm....df/11294738.pdf

 

UV irradiation:

 

http://www.fertstert...1227-8/abstract


Edited by catattack, 12 August 2016 - 01:09 PM.


#7 hyphaenation

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Posted 12 August 2016 - 06:25 PM

Intersting , thanks. Was an honest question.
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#8 Microbe

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Posted 13 August 2016 - 05:25 AM

https://www.cdc.gov/...ionMethods.html

#9 LordRigel

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Posted 19 August 2016 - 05:05 PM

Maybe microwaves can considered as a dessinfection method instead a sterlization method, 2014 papper ask about yeast and fungis who are, at a simple look of the literature, the principal enemies at the moment of fungal culture with the words "VIABILITY OF FUNGI DECREASED, VIABILITY OF ACTINOMYCETES INCREASED". For me when something got decreased and reach a full nutrients substrate will be recovered. 77's paper dont ask nothing about this matter, only about bacterias, and now I know they can be avoided with the microwaves in a high range. My knowleadge of phisics are very limited and cant uderstand how can work the another energy, the "non-thermal".

 

Thanks for the pappers, I read many experiencies with a microwave dessinfection vermiculite and maybe it work because vermiculite get a very high temperature, dont know rlly. I'll try an experiment with some strains of yeast and other ambient fungus like Aspergillus sp. in a vermiculite medium. How much time you put you vermiculite to "sterilize"?

 

Cheers.



#10 CatsAndBats

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Posted 19 August 2016 - 05:17 PM

I only use the microwave in a pinch if I'm pressed for time. I do three 2min runs with vermiculite that's at "field capacity", shaking in between runs with the lid on (lid is on loosely on top during the microwaving).



#11 goodnightmoon

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Posted 20 August 2016 - 06:03 PM

Eh, today I checked the resurrected shroom-site of my country (http://www.exkalapalatt.com/) and wondered, how many technologies to do sterilization with. 

UV-C germicid lights are used in hospitals, but if anyone are so eager to try that I should warm that one of the forum members really hurted oneself with that with just 2 mins of light on his eyes. I mean I doesn't get why anybody want to because there are easier methods, just saying. Be safe! :)


Edited by goodnightmoon, 20 August 2016 - 06:13 PM.

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#12 LordRigel

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Posted 21 August 2016 - 10:26 AM

Eh, today I checked the resurrected shroom-site of my country (http://www.exkalapalatt.com/) and wondered, how many technologies to do sterilization with. 

UV-C germicid lights are used in hospitals, but if anyone are so eager to try that I should warm that one of the forum members really hurted oneself with that with just 2 mins of light on his eyes. I mean I doesn't get why anybody want to because there are easier methods, just saying. Be safe! :)

 

These lights are very harmfull for eyes and skin if get exposed. I use one to sterilize a biosafety cabinet surface, completly closed and await from the room, the spectrum irradiate for 15min. These light cant be used to sterilize solid things, I guess only surfaces and some flats things.

 

That site is in which language? Look interesting, chinese for me.

 

Cheers.



#13 goodnightmoon

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Posted 21 August 2016 - 10:46 AM

@LordRigel:


 

Hungarian :)


Edited by goodnightmoon, 21 August 2016 - 10:46 AM.


#14 CatsAndBats

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Posted 19 April 2017 - 08:20 PM

This is a great little paper that I found today, it has very clear pros and cons of various disinfection, sterilizing, and sanitizing techniques.

 

Disinfection and Sterilization in Health Care Facilities:
What Clinicians Need to Know

 

Attached File  sterilization.pdf   242.57KB   45 downloads

 

 

 

 



#15 Ferather

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Posted 20 April 2017 - 01:01 PM

You can get microwave pressure cookers now, unless you get the expensive one the cheaper ones work ok.

Not a massive amount of internal pressure, but microwave + some pressure is still better  :)

 

MPC.png


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#16 CatsAndBats

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Posted 20 April 2017 - 01:02 PM

pressure, heat AND irradiation! cool!



#17 OysterFarmer

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Posted 07 November 2017 - 06:27 PM

Sterlized without pressure?

Depending on the level of sterility.  I've had good results achieving at least pasteurization with the water only method with straw.  Soak your straw until anaerobic bacteria predominates then pull it out and oxygen becomes the sterilant.  I've not done this with manure based substrates though.  Only straw.  Works great though.


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#18 Ferather

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Posted 07 November 2017 - 07:02 PM

@OysterFarmer, Interesting I've heard of this but never seen it. You should put out a write up, I know some people who would be interested.


Edited by Ferather, 07 November 2017 - 07:04 PM.

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#19 coorsmikey

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Posted 07 November 2017 - 07:56 PM

We need to split the topic I think if we are going venture into a new topic. But Check out this thread on cold fermentation/pasteurization.

cold-fermentation-an-alternative-for-heat-straw-pasteurization



cold-water-straw-fermentation

Cold Water Straw Fermentation

Cold water fermentation is an easy, fun, DIY technique for treating straw or other substrates for cultivation that doesn’t require the needless waste of wood or fossil fuels!

Simple and scalable, this method is a great technique to have in your toolbox if you’re doing low-tech cultivation. It prevents the cultivator from having to use fossil fuels and emit CO2 and doesn’t require any fancy equipment. Essentially a fermentation process, this method kills off competitors to your spawn by the simple act of submersion in water over a period of days. During the submersion process the anaerobic microorganisms live and grow while all the aerobic (oxygen loving) microorganisms die. When the water is removed after a week, the anaerobic bacteria die as soon as they are out in the open, leaving “clean” straw to use for inoculation. The process is quite simple and goes as follows:

1. Line a garbage can (or any hard, upright container) with a heavy duty (3 mil) trashbag, or find a big barrel that you’ll be able to dump.

2. Fill the bag with dry straw that has (ideally) been chopped with a weed whacker. I don’t personally have a weed whacker so I just break the straw up with my hands. But the increased surface area and smaller pieces provided by the use of this machine will enable better colonization and make handling easier later on.

3. Fill the can with water, covering the straw.

4. Add a weight on top to of the straw to keep it submerged. Big rocks and concrete blocks work well.

5. Put a lid on the can and keep it warm place, ideally in the sun.

6. Wait 7-12 days. If you’re in a warm environment, it’ll go a lot quicker than if you’re in cold environment.

7. At this point the water should be discolored and stinky. This is good, hopefully only anaerobic bacteria are still alive, and these will die when you expose the straw to air. You will now want to extract the straw from the water. If you decided to use a plastic bag inside of the barrel, twist up the top of the bag, poke some holes in it, and let the water drain out.

8. Inoculate your straw with Oyster, Shiitake, King Stropharia, Shaggy Mane, Blewit, or Elm Oyster spawn.



post-105498-0-65683400-1510103841.jpeg

More info compliments of barefoot Foods
cold-water-fermentation-pasteurizing-straw-without-heat/

COLD WATER FERMENTATION: PASTEURIZING STRAW WITHOUT HEAT
Straw is a very common commercially popular substrate for the cultivation of a wide variety of different edible and medicinal mushroom species, and thanks to the folks over at Radical Mycology, I am now aware of an alternative method of preparing the straw for colonization with mycelium. There are many fungi that grow well in pasteurized straw, including but certainly not limited to many species comprising the oyster mushroom genus (Pleurotus spp.) as well as paddy straw mushrooms (Volvariella volvacea) and shaggy manes (Coprinus comatus) among others. For the most part, straw is easy to obtain and process and this has made it one of the ideal material choices for commercial mushroom growers. To the opportunistic and innovative mushroom grower, straw makes a prime candidate for experimenting as a suitable substrate for mushroom cultivation. In order to successfully grow mushrooms using straw, it must be pasteurized or ‘cleaned’ of most if not all harmful fungal spores, bacteria or other pathogens before it can be mixed with mushroom spawn.

Now before I can continue there is a discrepancy which must be firmly addressed. Pasteurization and sterilization, despite sounding like quite similar processes, are in reality fundamentally different and result in different outcomes. By sterilizing a substrate (if the process was successful) you have managed to kill every living thing on the surface of that material that you have sterilized. This can be compared to starting off with a ‘blank canvas’ where anything that you introduce onto the substrate ought to be the only living thing in contact with that material. Pasteurization, on the other hand, is slightly different. Renowned mycologist Paul Stamets says it best in his book Growing Gourmet and Medicinal Mushrooms: “Pasteurization selectively kills off populations of temperature sensitive microorganisms. The population intact represents little competition to the mushroom mycelium for approximately 2 weeks, giving ample opportunity for the mushroom mycelium to colonize.”

Essentially, pasteurization removes many of the harmful bacteria and fungal spores that may compete with the fungi that you are attempting to introduce to the substrate. Additionally, the heat-tolerant microorganisms remaining in the straw after pasteurization help to prevent contamination from unwanted microorganisms (a.k.a. ‘baddies’) because their niches are already being occupied by the harmless or inert populations of microorganisms. These remaining ‘goodies’ may even aid in/assist with the growth and development of the fungus itself. There are three different methods that I will discuss here that can be done to pasteurize straw: hot water immersion, steam pasteurization and pasteurization through natural fermentation.

Hot water immersion involved steeping the straw (often pre-cut to approximately 1-4 inch lengths to make handling easier) in 160-180 °F water for at least 1 hour but not more than 2. It helps to have something weighing down on the straw to help keep it submerged. The temperature of the water, as discussed above, kills heat-sensitive fungi and bacteria that may be harmful to your mycelium but leaves beneficial or inert microorganisms unscathed. After the hot water bath, the straw is transfered to perforated racks where it can cool and drain before it can be further processed. Steam pasteurization results in exactly the same outcome except that high-pressure steam is released into heavily insulated rooms or containers containing pre-moistened straw arranged in layers on drainage racks. This option, in my humble opinion, is the least practical for the home mushroom grower as specialized equipment is pretty much entirely necessary. Considering that hot water immersion can be performed in a pot, on any stove or heat source, in any home (or fire pit) I believe it to be the more economical and less labor-intensive method. Edit: another important piece of information: after being pasteurized, the straw can be safely handled with your hands (as long as they are reasonably clean) to be drained and stuffed into containers without overly increasing the risk of contamination. If you want to be extra careful you could wear rubber/latex gloves although either way you should expect not to have perfect but still fairly high successful colonizations.

The last technique, pasteurization through natural fermentation, is by far the least energy intensive but takes considerably longer than the other methods. (Check out the original article right here by Radical Mycology for more information) The principal here is that by immersing the straw in cool, fresh water (chlorinated tap water is not recommended to be used when working with fungi due to it’s anti-microbial and anti-fungal properties; rain, well or filtered water is preferred) for 3 or 4 days which allows anaerobic microorganisms to flourish and multiply on the substrate, creating a rich biological complexity which kills fungal spores or aerobic bacteria. Don’t worry too much about the ‘appetizing’ (hint extreme sarcasm) aroma that emanates from the container after this fermentation period as straining the soaking straw and exposing it to oxygen not only gets rid of the odor but also then kills all of the oxygen-hating anaerobic microorganisms, leaving you with a ‘blank canvas’ which you can then inoculate with your mushroom mycelium.

This last method seems the most sustainable and energy efficient option for pasteurizing particularly large volumes of straw or other bulk substrates for the purpose of mushroom growing, but as Stamets once again says later on the same chapter “I hesitate to recommend it [pasteurization through natural fermentation] over the other procedures described here.” Staments makes this comment on the basis that this method may not be as successful to ‘clean’ the straw and subsequently result in more contamination than the two other heat-treatment methods. Despite this, depending on the condition of your substrate, your working environment and your personal view of cleanliness when working with mushrooms, your results may vary. I would still consider this just as much of a legitimate method as all the others purely on the basis that it can be conducted by virtually everyone living anywhere and therefore makes the possibility of growing mushrooms for food or medicine more plausible for the average individual; a principal that I am pretty much all about promoting.

For additional information pertaining to pasteurizing straw and other bulk substrates for mushroom culture, check out this and this. Earlier this week I tried out the hot water immersion method (being careful to watch the thermometer to make sure the water temperature didn’t leave the 160-180 °F range) and will report on the results as soon as they happen. I mixed the pasteurized straw with an old jar of Pleurotus columbinus mycelium which I broke into pieces with my clean hands (I washed them several times with soap every few minutes during this whole procedure) and mixed them with the drained and cooled pasteurized straw before packing the mixture into jars and topping them with a double layer of aluminum foil. They will now incubate at room temperature (roughly 70 °F) and I’ll await some mushroom magic.


Edited by coorsmikey, 07 November 2017 - 08:29 PM.


#20 OysterFarmer

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Posted 07 November 2017 - 08:03 PM

@OysterFarmer, Interesting I've heard of this but never seen it. You should put out a write up, I know some people who would be interested.

I was actually doing it before Paul Stamets did a piece on it.  I moved away from it because I thought my results were just coincidence or a fluke.  Then I saw him posting videos of it and was kicking myself I didn't do a write up before that!

 

That's the gist of it though.  Only a couple more fine points that people would need a full write up to understand.  I'll probably have time in a few days to write it out.






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