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Thread: autoclave vs pressure cooker for lab

  1. #1
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    autoclave vs pressure cooker for lab

    We have an old autoclave that was given to us when we began our lab program about a year ago. I think it is about to die and I need to replace it, but can't afford a new autoclave right now. I am looking into pressure cookers, but I cant find any clear guidance on the pressure/temp requirements for sterilizing, so I am unable to evaluate if a $100 pressure cooker will do the job. Can anyone out there offer some guidance on if a pressure cooker (seems like most are limited to 10-12psi) will suffice for sterilization, and if so, what the time requirements are?

    Alternatively, if anyone has any good leads on affordable/used autoclaves, I am all ears.
    Kevin Drake
    Alibi Ale Works
    North Lake Tahoe

  2. #2
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    I'm not sure what pressure you need off the top of my head. I know you need a minimum temp of 250 oF or 121 oC for 15 min to be considered sterile (that seems to be the standard for bio lab work)
    I would guess that a steam table could get you the info on what pressure that is, I think its right around 15 but I'm not sure anymore.
    Manuel

  3. #3
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    Palatine, IL
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    What do you plan on sterilizing?

    I use a pressure cooker as our autoclave. It's a Presto 01781 23qt. No complaints after 2 years of use. It can fit 2L Erlenmeyer flasks.

    Sterilization is most commonly done at 121C for 15min. This is 15psi of steam pressure. A quick google search will give you sterilization times at given temperatures.

    The big drawback to pressure cookers is the inability to dry items in the pressure cooker. I had to give up on glass petri dishes because of condensation in the dishes. This was solved with sterile disposable petri dishes (nobody uses glass petri dishes anyways).

  4. #4
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    Thanks Jeff. We are using it in our lab to produce sterile media for basic brewery micro work. I think I'm going to go for a pressure cooker like the one you have (with a pressure gauge) and buy an electric hot plate for it, rather than getting an electric plug-in type pressure cooker, since none of them seem to have a PSI read-out anywhere. And like you, we are big fans of sterile disposable petri dishes and other lab-ware.
    Kevin Drake
    Alibi Ale Works
    North Lake Tahoe

  5. #5
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    Quote Originally Posted by thedrake View Post
    Thanks Jeff. We are using it in our lab to produce sterile media for basic brewery micro work. I think I'm going to go for a pressure cooker like the one you have (with a pressure gauge) and buy an electric hot plate for it, rather than getting an electric plug-in type pressure cooker, since none of them seem to have a PSI read-out anywhere. And like you, we are big fans of sterile disposable petri dishes and other lab-ware.
    Kevin,

    Sounds like that will do the trick. I use a very cheap Aroma brand 1000Kw hot plate. It works well for the pressure cooker/autoclave, boiling media, diacetyl tests, etc. A stirring hot plate would be a good idea but I've gotten away without one.
    Last edited by AT-JeffT; 03-19-2017 at 12:56 PM.

  6. #6
    Join Date
    Oct 2013
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    Calgary, Alberta, Canada
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    Hi Kevin,

    When we setup our lab a few years ago we purchased an electric sterilizer form Cynmar. We purchased back in 2013 and have only had to replace the the thermostat since then. other than that it's been pretty low maintenance. I like it as I can make larger batches of media per run and sterilize a lot of sample jars as per run. I also use it for dilution blanks and swabs. It has a gauge for pressure/temperature as well. Here is a link to the model we purchased.

    http://cynmar.com/autoclaves-accesso...1-qt-120V.html


    Wendy

  7. #7
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    United States
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    I use an All American pressure cooker. I bought some autoclave tape to help me make sure I get up to temp. I rock out at 15 psi for 10 minutes when I'm doing media. If I'm sterilizing stainless it's 15 psi for 15 minutes. Going on 4 years with this thing, and so far so good. I use a propane burner like you would deep fry a turkey with to heat it. The only thing is that sometimes folks walk away and keep it unattended. So it's constant nagging about safety.

  8. #8
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    St Louis, MO
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    Quote Originally Posted by upakriek View Post
    The only thing is that sometimes folks walk away and keep it unattended. So it's constant nagging about safety.
    This is one of the strongest benefits to getting an autoclave. You can press a button and come back when it's done. A pressure cooker will be capable of sterilizing, but it really boils down (pun intended) to how much time in your day you have available to commit to sterilization.

  9. #9
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    Dec 2015
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    Raleigh, NC, USA
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    Pressure cookers work fine, but they do have the aforementioned lack of drying problem, and I also find space to be an issue. I generally have to lay my flasks down to get everything in there.

    The steam function for 15 minutes on mine does the trick. You can get autoclave tape to make sure you are meeting the proper temp/pressure guidelines.

  10. #10
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    milwaukee
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    autoclaves have filters for the air that comes in to break the vacuum that will form during cool down.

    a presto 23q is a great tool but understand that room air will be drawn in from the jiggle weight on the top. this may require filtered gas exchange lids on media rather than being just loosened lids. Mycologists will cover with an alcohol rag when making spawn so air drawn in is "cleaner"

    a All American sterilizer is a bit different it uses a toggle valve rocker rather than the weight. it will hold a vacuum. you can break the vacuum in front of a flow hood to suck in clean air. also with say a presto pressure cooker you could put it in front of a hood to cool down immediately after the cycle.

    They both lack a dry cycle but they are great for sterilizing media

    The most important thing about using a pressure cooker or sterilizer rather than an autoclave is the need to vent

    you need to vent your cooker / clave at least 10 minutes to remove air. if you pressurize air daltons laws take effect and you will not be at 15psig of steam pressure thus not at 250F or 121C if even 5% air is entrapped you will see 15psi on your gauge but the temperature inside will be a few degrees lower.
    I hope I encouraged you!

  11. #11
    Join Date
    Apr 2013
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    monmouth, IL USA
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    parts for autoclave

    manual autoclaves are almost always repairable Parts are fairly available for even older autoclaves.

    What brand is it and what is the problem?

    s

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