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Using a soft, non-abrasive cloth, antibacterial dish soap and warm water, gently clean and rinse the plastic Petri dishes. The Petri dishes should be free of all debris, including any soap residue. Place the Petri dishes into the sterile bleach solution, one at a time, for approximately two minutes each.The process of killing or removing all microbes capable of reproduction is called sterilization, and it can be accomplished by both physical and chemical methods. For pre-wrapped petri dishes, however, the most effective technique is exposure to ionizing gamma radiation or electron beams.But where organisms are isolated and grown as pure cultures, sterile containers are required. For this kind of work, many schools cannot afford glass petri dishes and an autoclave or hot-air oven. Disposable plastic petri dishes are considerably less expensive than glass, but they cannot be sterilized by heat.
Contents
Which technique is used to sterilize plastic petri plates?
The process of killing or removing all microbes capable of reproduction is called sterilization, and it can be accomplished by both physical and chemical methods. For pre-wrapped petri dishes, however, the most effective technique is exposure to ionizing gamma radiation or electron beams.
Can I autoclave plastic petri dishes?
But where organisms are isolated and grown as pure cultures, sterile containers are required. For this kind of work, many schools cannot afford glass petri dishes and an autoclave or hot-air oven. Disposable plastic petri dishes are considerably less expensive than glass, but they cannot be sterilized by heat.
Can you pressure sterilize plastic petri dishes?
There are many heat resistant containers that can withstand being pressure cooked, but disposable plastic petri dishes are not one of them. You could use glass or pyrex petri dishes, baby food jars, or you could use any food grade plastic container that are made to heat food in the microwave.
What temperature do plastic petri dishes melt at?
The melting temperature of the raw material used during their manufacture is approximately 250°C. This is considered to be sufficient to destroy bacteria. The dishes are packed under very strict aseptic conditions. Sterilised petri dishes are recommended for microbiological tests.
How many hours should the petri dishes be sterilized?
Petri dishes in polypropylene bags, exposed to 250°F for 70 minutes, required more than 65 minutes to reach temperature. The corresponding time for petri dishes in polyethylene bags was 48 minutes.
Can you microwave petri dishes?
The case for using microwave ovens for decontamination of cultures or materials was made back in 1977 by Latimer and Matsen. They showed that 1-5 minutes in a conventional microwave was sufficient to decontaminate 5mL cultures or petri dishes of common clinical pathogens including E. coli, S.
Are petri dishes dishwasher safe?
Excellent for general laboratory applications, including cell culturing, plant germination, precipitate drying and solvent evaporation, home or classroom science experiments, crafting, small storage solutions and more. Reusable and simple to clean. Top rack dishwasher safe.
Do you have to autoclave petri dishes?
Standard protocol requires the use of autoclaves to sterilize petri dishes, as only high heat and pressure can effectively kill the full range of microorganisms, which can persist even under unusually harsh conditions.
Why must petri dishes be Sterilised before use?
Glass petri dishes and agar gel must be sterilised before use by using an autoclave , or pre-sterilised plastic petri dishes can be bought. Reason – this will kill any unwanted bacteria that are present in the solution or on the petri dishes.
What can I use instead of autoclave?
- Ionizing Radiation.
- Dry-Heat Sterilizers.
- Liquid Chemicals.
- Performic Acid.
- Filtration.
- Microwave.
- Glass Bead “Sterilizer”
- Vaporized Hydrogen Peroxide (VHP®)
Can you autoclave plastic?
Safe plastics to autoclave include polycarbonate, polypropylene, polypropylene copolymer, and fluoropolymer containers; however, few types of resins must be sterilised with gas and not through autoclaving.
Can you sterilize agar in a microwave?
While wearing heat- protective gloves, carefully remove the hot bottle and let it cool to between 75–55°C before pouring. c) Microwave: Loosen the cap on the agar bottle before microwaving. Heat in one minute intervals on low power until all of the agar is melted.
Why is autoclaving the best method for sterilization?
Autoclaving is better than boiling because it can generate much higher temperatures where microbes that are boiling-resistant cannot survive. Steam sterilisation is highly efficient, making it one of the most reliable forms of sterilisation. Autoclaving can be used on various instruments.
Why petri dishes must be sterilized?
Glass petri dishes and agar gel must be sterilised before use by using an autoclave , or pre-sterilised plastic petri dishes can be bought. Reason – this will kill any unwanted bacteria that are present in the solution or on the petri dishes.
Can you autoclave agar?
Autoclave
Autoclave your medium for 25 minutes. After autoclaving, you can of course store the medium-agar mix in a toughened glass bottle then melt it in a microwave or water bath when needed. Make sure you use toughened glass bottles, or disaster (see #2) can strike.
What is the process of sterilization?
Sterilization describes a process that destroys or eliminates all forms of microbial life and is carried out in health-care facilities by physical or chemical methods.
How to Sterilize Petri Dishes | Sciencing
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- Summary of article content: Articles about How to Sterilize Petri Dishes | Sciencing Updating …
- Most searched keywords: Whether you are looking for How to Sterilize Petri Dishes | Sciencing Updating Petri dishes are a common item found in both professional and educational science labs. Unfortunately, budget restrictions force companies and educational establishments, such as high school and college biology labs, to reuse the Petri dishes. The disadvantage of reusing Petri dishes is the increased ability to …
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What Could Be Used to Sterilize Plastic Petri Plates in a Plastic Wrapper? | Sciencing
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- Most searched keywords: Whether you are looking for What Could Be Used to Sterilize Plastic Petri Plates in a Plastic Wrapper? | Sciencing Updating When scientists conduct microbiology experiments, they need to make sure that no unexpected microorganisms are growing in their petri dishes and test tubes. The process of killing or removing all microbes capable of reproduction is called sterilization, and it can be accomplished by both physical and chemical methods. …
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Shooting for Sterilization
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how to sterilize plastic petri dishes at home
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🔬 How to sterilize equipment such as petri dishes | Amateur Microscopy – YouTube
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- Most searched keywords: Whether you are looking for 🔬 How to sterilize equipment such as petri dishes | Amateur Microscopy – YouTube Updating There are different ways of sterilizing labware and culture media. I want to give an overview here.🎈 SUPPORT THE CHANNELBecome a Patron: https://www.patreon…microscope, microscopy, microbehunter, microbes, microorganisms, sterilization, culture media, microbiology, petri dish
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EdvoTech Tips: Sterilization without an Autoclave – YouTube
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- Most searched keywords: Whether you are looking for EdvoTech Tips: Sterilization without an Autoclave – YouTube Updating In our first EdvoTech Tip video, we describe an easy and cost-effective way to sterilize media, reagents, and equipment in the teaching laboratory! This sim…Edvotek, biotechnology, education, biology education, Biotechnology education, autoclave, microbiology, molecular biology, sterilize, sterilization, bacteria, instant pot, pressure cooker, lab hack, laboratory hack, low cost laboratory, tech tip, technical tip, biology teacher, science teacher, science education, homeschool, homeschool science, bacterial transformation, sterile media, bacteriology, low cost, bacteria media, nutrient agar, nutrient broth, agar plates, life science
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TEK: Sterilizing Plastic Petri Dishes – Mushroom Cultivation – Shroomery Message Board
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- Summary of article content: Articles about TEK: Sterilizing Plastic Petri Dishes – Mushroom Cultivation – Shroomery Message Board put water bleach solution in a container large enough to fit the petri dishes. also make sure the water is warm enough but not too hot to melt … …
- Most searched keywords: Whether you are looking for TEK: Sterilizing Plastic Petri Dishes – Mushroom Cultivation – Shroomery Message Board put water bleach solution in a container large enough to fit the petri dishes. also make sure the water is warm enough but not too hot to melt … I know its not practical but I got myself in a situation where I got stuck with plastic petris and had no choice but to experiment. here’s what i did so far. what i used: 12 used petri dishes with
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how to sterilize plastic petri dishes at home
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- Summary of article content: Articles about how to sterilize plastic petri dishes at home noticed that the plastic Petri dishes melt when I put them into the … biohazard bag and place it in the autoclave to be sterilized, … …
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US4417926A – Method for cleaning and disinfecting used plastic Petri dishes
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– Google Patents Contaminated plastic waste material in the form of used Petri dishes, so-called agar plates, is rendered harmless and cleaned by placing the agar plates in … … - Most searched keywords: Whether you are looking for US4417926A – Method for cleaning and disinfecting used plastic Petri dishes
– Google Patents Contaminated plastic waste material in the form of used Petri dishes, so-called agar plates, is rendered harmless and cleaned by placing the agar plates in …
Contaminated plastic waste material in the form of used Petri dishes, so-called agar plates, is rendered harmless and cleaned by placing the agar plates in a bacterium-tight heating chamber maintained substantially at atmospheric pressure and contacting them with water at an elevated temperature, preferably 90°-98° C. for a predetermined period of time. After the predetermined period the agar plates are rinsed with water which is then drained off through an outlet in the bottom of the heating chamber. The agar plates to be treated are loaded into the heating chamber in batches contained in bags wholly or partly consisting of a plastic sheet material which is solid and substantially insoluble in water at room temperature but soluble in water at the elevated temperature. Invention makes use of a property of agar plates, namely that the dishes and/or lids thereof warp due to internal stresses in response to the heated water to thereby open them up in the bacterium-tight heating chamber to enable internal cleaning and rinsing. - Table of Contents:
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how to sterilize plastic petri dishes at home
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- Summary of article content: Articles about how to sterilize plastic petri dishes at home LINCOLN, P. A., G. D. BREACH, and J. G. DAVIS. 1965. The ac- tivity of sodium hypochlorite against Canda albicans in milk suspensions and … …
- Most searched keywords: Whether you are looking for how to sterilize plastic petri dishes at home LINCOLN, P. A., G. D. BREACH, and J. G. DAVIS. 1965. The ac- tivity of sodium hypochlorite against Canda albicans in milk suspensions and …
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How to Sterilize and Dispose Plastic Agar Plates and Petri Dishes
Last Updated on June 24, 2022
A Messy Affair: Sterilizing and Disposing of Used Agar and Petri Dishes
Agar plates, otherwise known as Petri dishes, serve as an integral and irreplaceable part of microbiological research, particularly in their functional and utilitarian role in culturing bacteria, fungi, and other microorganisms.
Though relatively easy to prepare and requiring a minimal amount of equipment to culture, clean-up and disposal can be a messy affair, requiring the user to undertake procedures to sterilize and minimize the risk of potentially harmful microorganisms contaminating both inside and outside the laboratory environment.
Standard protocol requires the use of autoclaves to sterilize petri dishes, as only high heat and pressure can effectively kill the full range of microorganisms, which can persist even under unusually harsh conditions. Alternative agar petri dish sterilization methods not requiring the use of autoclave sterilizers, such as microwave ovens or caustic chemicals, have been recommended in place of using autoclaves. However, these methods have been proven ineffective because of the resistance of certain microorganisms.
The method in which we place petri dishes in bio-waste/biohazardous waste bags and sterilized them in autoclaves has become the standard protocol at many laboratories. However, this method comes with downsides, as liquified agar mixed with biomaterial can easily leak and cause an enormous mess within the laboratory or on its way to waste disposal areas and beyond. When paired with the correct autoclaving accessories, the autoclave sterilization method for plastic agar plates/Petri dishes can be both effective in deactivating harmful microorganisms and preventing an enormous mess.
Please find below the following plastic petri-dish agar plate sterilization and disposal method using an autoclave sterilizer, broken down into a few easy steps.
1. Collect Used Plates
Collect used Petri dishes/culture plates with agar. Cultured agar plates/Petri dishes should be left as is with agar and covered to prevent the spread of microorganisms and reduce the risk of contamination.
2. Load Agar Plates/Petri Dishes
Load used culture plates in the plastic petri dish/agar plate sterilization basket. Removing covers and placing them aside before loading the agar-filled portion into the specialized perforated basket. Place dish/plate covers on top of the agar-filled portions at the end.
3. Set Up Bucket and Stand
Set up the stand inside the specialized solid bucket and fill it with water to prevent melted media from solidifying inside the bucket. The stand will place the specialized perforated basket on top of the water to allow the melted media to fall through. Fill water to about half of the height of the stand.
4. Load Bucket with Stand
Place the water-filled bucket inside the autoclave. Next, place the perforated basket with disassembled plastic Petri dishes/agar plates, resting the basket on the stand.
5. Run Cycle
Close autoclave and run a normal sterilization cycle for at least 20 minutes. Please note that the sterilization time differs with the number of plastic Petri dishes/agar plates.
6. Unload
After the sterilization cycle is complete and the autoclave temperature has cooled down to a safe level, remove the perforated basket. Even though the temperature is registered at a safe level, please be mindful of hot steam, liquids, and media.
7. The Chunk
Note that the plastic Petri dishes/culture plates and lids have melted and re-forged into a sizeable chunk. Some of the agar material has been trapped/fused into the plastic, and though it should be sterile, avoid touching parts where agar is exposed to prevent a mess. Most of the agar has melted and mixed with the water inside the bucket.
8. Throw Away- No Mess!
Dispose of the plastic chunk and pour water into a biohazardous liquid receptacle or a drain where it can be safely disposed of and eventually processed. Safe, easy, and no mess!
A Means to a Mess
Agar plates, otherwise known as Petri dishes, serve as an integral and irreplaceable part of microbiological research, particularly in their functional role in culturing bacteria, fungi, and other microorganisms. Though relatively easy to prepare and requiring a minimal amount of equipment to culture, clean-up and disposal can be a messy affair, requiring the user to undertake procedures to sterilize and minimize the risk of potentially harmful microorganisms contaminating both inside and outside the laboratory environment.
Standard protocol requires the use of autoclaves to sterilize Petri dishes, as only high heat and pressure can effectively kill the full range of microorganisms, which can persist even under unusually harsh conditions. Alternative agar petri dish sterilization methods not requiring autoclave sterilizers, such as microwave ovens, have been recommended in place of using autoclaves. However, these methods have been proven ineffective because of the resistance of certain microorganisms. The method by which we place Petri dishes in bio-waste/biohazardous waste bags and sterilize them in autoclaves has become the standard protocol at many laboratories. However, this method comes with downsides, as liquified agar mixed with biomaterial can easily leak and cause an enormous mess within the laboratory or on its way to waste disposal areas and beyond. When paired with the correct autoclaving accessories, the autoclave method is the most effective agar dish and plate sterilization method.
As you can see, petri dish sterilization can be done safely and easily with little mess, decimating the risk of contamination.
If you are interested in the aforementioned agar sterilization accessories or the compatible TOMY SX-Series autoclaves,
please fill out a contact form and one of our sales representatives will get back to you shortly.
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TEK: Sterilizing Plastic Petri Dishes
Some of these posts are very old and might contain outdated information. You may wish to search for newer posts instead.
I know its not practical but I got myself in a situation where I got stuck with plastic petris and had no choice but to experiment.
here’s what i did so far.
what i used:
12 used petri dishes with the opened plastic bag/wrap that came with it.
95% isopropyl alcohol
bic lighter
dinner plate
allot of napkins/ paper towels
microwave
a. clean
open the lid of the petri dishes and pour some h2o2 over the used up agar. close lid.
wait for bubbles to subside. open the lid and remove the agar from the petri dish.
i used a butter knife to lift the sides then throw them in the garbage.
dispose agar properly in a closed plastic bag. (or incinerate/ dump in hot water)
b. soak
put water bleach solution in a container large enough to fit the petri dishes. also make sure the water is warm enough but not too hot to melt the plastic. i used “almost” boiling water and added some normal temp water to control the heat.
soak empty petri dishes in a container with water bleach solution. make sure the petri dishes are separated from the top and bottom parts. and make sure you have enough water/bleach to cover the petri dishes.
cover container to maintain temp until water comes to room temp.
drain water from container and rinse petri dishes with a wash of lukewarm water to remove soap, suds or excessive bleach.
drain lukewarm water and get ready to assemble dishes.
c. re assembly/ drying
put the petri dishes back together while using a cotton ball dabbed in some alcohol (not too wet, just enough to sanitize) to dry the inside parts of the petri dishes. (i prefer to do this in still air)
i wipe the petri dishes’ inside part facing down as to be careful not to expose the inside to falling contaminants (if that makes sense?).
close petri dishes right after you dry the inside with cotton. stack them up nicely and from this point on, we will be calling this “the left stack”
d. alcohol blasting
this is the tricky part. you would need high 95% alcohol or higher.
the prep:
prepping is key as i stack them at a manageable height, i put them on my left side so i can use my left hand to bring the petri dishes over to my middle where my alcohol sanitized dinner plate is (this is where we will do the blasting). i also make sure that i have space to my right where i can stack them after i alcohol blast them.
put the alcohol in a clean container where a syringe can be loaded in place and suck some alcohol in.
for visual pusposes i shall name the objects in this process
left stack: this stack is where you will be getting your petri dishes FROM
middle: this is where you will transfer petri dishes one plate at a time and do the blasting
right stack:from the middle stack, this is where you will be moving the petri dishes TO
here is the diagram:
[image] [/image]lets do this:
using left hand, get one petri from left stack and place the in the middle plate. with your right hand,get the alcohol loaded syringe and point it to the inside part of the petri while you slightly lift the cover from the petri dish. lift cover just enough to spray alcohol inside to put enough alcohol(doing it just like innoculating lc to agar). no need to spray all over insides as next step will cover that. close the lid.
after the lid is closed, shake the petri dish so that the alcohol will uniformly be coating the inside. excess alcohol can be drained from the sides of the petri dish. just tilt it so you can remove excess alcohol. wipe the outside with alcohol dabbed clean cotton and remove excess alcohol. wipe the plate dry as well and then, put the petri dish back at the middle plate.
now… get a bic lighter.. you know where im getting at here? this stuff needs more practice than any of the things weve done here so far.
same motion as innoculating lc to agar, but this time well blow things up. for those who do not know, this will create a small gas explosion as we light up the lighter next to a semi opened petri dish cover.
so… using your left hand, lift the cover enough for an gap to light the gas inside with a lighter on your right hand.
be aware that after the explosion, you have a millisecond the put the flame out by replacing the lid to cut air and kill the flame. the longer you kill the flame with the lid, the more chances of you melting your PLASTIC PETRI dish.
as a tip i would advice to lift te cover slightly but still close enough to make sure that when you release the cover, it sill still fall alligned to the bottom dish therefore shutting it without aiming. i used my ears more for this drill as when i hear the poof, i release the cover and shutting it.. once done, move the blasted perti to the right stack.
REPEAT until finished.
e. microwave drying
now you have your right stack, hopefully your left with a most of your plastic petris intact. ( i lost 2 out of 12)
if you still have the plastic sleeve/ container of your plastic petris i would put them back now but i suggest you put a layer of clean/ sterile cloth in between the plastic container and the petri dish. assuming that you follow how the others do it, you should end up with the open side of the plastic bag at the bottom and the sealed part at the tom part of the stack. now place it inside the microwave, make sure the plastic open side is facing up (top side down). you want to do this so the hot gases escape while we heat the petris.
heat at medium until no more water is visible inside the petris. id suggest you open the mocrowave and check on your petris every now and the to monitor heat build up.
VOILA.
next logical step is to fill it with weak peroxide/agar solution.
will post pics soon.
Extras: Top
Probably would have been better off not even trying to resterilize them. Unless they were contaminated with mold or around the edges with bacteria you probably could have gotten away with reusing them as is just by removing the old agar.
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Extras: Top
thanks for the feedback, are you saying that if the agar is not that contaminated on the side, you can get away with just washing it? or dou you just remove the agar and re pour agar on them? thats good info..
on my case it is contaminated with allot of diff contams. ill try that sometime though. thanks.
Extras: Top
I haven’t actually reused a plastic dish, just theory. But the agar I use sticks together well enough I can remove it pretty thoroughly just with my scalpel so dish is pretty much empty. Assuming it is still sterile I don’t see any reason you couldn’t pour new agar in… depending on what you were using it for I suppose, there could still be some traces of mushroom mycelium in it.
BTW, if you have some polypropylene containers they can be pressure cooked and used as dishes or you could use mason jars. They’re a pain in the ass when trying to cut small wedges, but it’s an option to consider.
——————–
Edited by Kizzle (04/23/14 01:58 AM)
Extras: Top
If that works for you and you don’t mind doing it, great but I wouldn’t suggest this technique to anyone.
There seems to be a lot of unnecessary steps like pouring peroxide over the old agar before removing it. Wiping the petris down with alcohol after they’ve already been soaked in bleach also seems pointless. The crazy part is where you suggest lighting the alcohol on fire to create an “explosion”. Aside from being dangerous, it basically provides no benefit as far as sterilization goes since the only thing burning is the alcohol vapors and not the alcohol itself or possible contaminants present in it. If you were to accidentally spill your bottle of alcohol or aren’t paying attention while creating these explosions you could catch your work area, clothing or even your house on fire. Microwaves are likely to melt petris if not monitored carefully and they aren’t a clean environment for drying anything.
I’d look into purchasing glass petris if you absolutely need reusable ones or just buying more. This tek is super sketchy all around.
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Quick WBS Prep
Extras: Top
just buy them by the case. or use pasty white tek with snap top pp5
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A few thoughts on cultivation
MICROBIAL HUSBANDRY!!!!
The whole is greater than the sum of its parts
Extras: Top
fyi: in case your thinking of trying it. plastic petri plates are presterilized with uv light or irradiation. they will warp and melt at about 12 psi or 245 degrees F. At 15 psi, they become a big ass mess. In other words, dont bother trying to pc them.
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All this to save 25 cents, which is the most I’ve ever paid for pre-sterilized petri dishes.
RR
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Download Let’s Grow Mushrooms
semper in excretia sumus solim profundum variat
“I’ve never had a failed experiment. I’ve only discovered 10,000 methods which do not work.”
Thomas Edison
Extras: Top
Quote:
RogerRabbit said:
All this to save 25 cents, which is the most I’ve ever paid for pre-sterilized petri dishes.
RR
I searched for about an hour and the cheapest ones I could find cost me a buck a piece after shipping. The only way I could get them cheaper than that would be to order 500 at a time.
——————–
AMU
Bottle Tek
Liquid Inoculant Tek
Extras: Top
Its probably just because I live in Canada. every time I found a good price they either didn’t ship to Canada or the shipping was three times the price of the dishes.
——————–
AMU
Bottle Tek
Liquid Inoculant Tek
Extras: Top
even when u order a case of 100 they are that expensive?
——————–
A few thoughts on cultivation
MICROBIAL HUSBANDRY!!!!
The whole is greater than the sum of its parts
Extras: Top
I was looking for cases of 100 but ended up only getting 60 because I couldn’t find them cheep enough. I found a decent price at one of the sponsers but they don’t take MasterCard and I just cancelled my Visa.
——————–
AMU
Bottle Tek
Liquid Inoculant Tek
Extras: Top
…this was my first time with plastics…had no clue you couldn’t fill with agar,then PC. At 15 psi for half hour…wasn’t really thinking!!!…
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…I’d much rather be fishing,!!!
Extras: Top
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I t d o e s n ‘ t m a t t e r w h a t i t h i n k o f y o u . . . a l l t h a t m a t t e r s i s c l e a n s p a w n
I’m tired do me a favor
Extras: Top
is this a new tek?
——————–
A few thoughts on cultivation
MICROBIAL HUSBANDRY!!!!
The whole is greater than the sum of its parts
Extras: Top
Quote:
BennD.42 said:
…this was my first time with plastics…had no clue you couldn’t fill with agar,then PC. At 15 psi for half hour…wasn’t really thinking!!!…
Yup, that’s why they’re called disposable
There are some that can be resterilied though.
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Extras: Top
My plastic petri dish sterilization tek
light a fire
get it real hot
throw the petri dishes on
job done!
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T h e n e a r e s t w e e v e r c o m e t o k n o w i n g t r u t h i s w h e n w e a r e w i t n e s s t o p a r a d o x .
Extras: Top
Quote:
MudaFuka said:
Quote:
RogerRabbit said:
All this to save 25 cents, which is the most I’ve ever paid for pre-sterilized petri dishes.
RR
I searched for about an hour and the cheapest ones I could find cost me a buck a piece after shipping. The only way I could get them cheaper than that would be to order 500 at a time.
Same down here mate… EBay has got a bit cheaper this year though (halved in price actually), about 7 bucks for 10 delivered. Still pretty steep.
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T h e n e a r e s t w e e v e r c o m e t o k n o w i n g t r u t h i s w h e n w e a r e w i t n e s s t o p a r a d o x .
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I’ve had success with resterilizing plastics with chlorine gas.
I place them face down on a cookie cooling rack in side a SAB to allow the gas to contact the underside of the first layer, you can stack them a few high as long as they’re staggered to allow the gas to enter each dish. Add a glass jar with a bit of TCCA (available at a pool store and Wal-Mart during the summer) and just add a couple drops of hcl and close it up. After a hour your dishes are sterile, open the arm ports and reassemble the plates and store.
Reduce. Reuse. Recycle. Only trash goes in the trash. To each his own though
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AMU Q&A Thread because questions deserve answers.
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Quote:
Is that a metal one piece lid used as a petri?
Boom, 25 for $10.95 shipped
also 25 for $9.50 plus shipping
Also
Pastywhyte’s “Easy Agar” Tek using $3 for 8 miniglads that can be PCed and reused. Point being, all that you just went though was a whole lot of (potentially dangerous) work, for little benefit and saved very little cash. I’d rather pay for the dishes and save my time.
The lid makes up part of one yeah.
What’s potentially dangerous about reusable petris?
$10 isn’t a lot of money but 25 dishes aren’t going to go very far either. You’ll probably be ordering more in a few months. They run out at the worst times. They need special storage considerations since a sleeve can be damaged or opened by accident. If you do anything that might compromise the sterility of a disposable dish your only option is to throw it out or to risk using it anyway.
Cleaning out petris dishes is extremely easy as is sterilizing them.
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Quote:
Kizzle said:
Quote:
Is that a metal one piece lid used as a petri?
Boom, 25 for $10.95 shipped
also 25 for $9.50 plus shipping
Also
Pastywhyte’s “Easy Agar” Tek using $3 for 8 miniglads that can be PCed and reused. Point being, all that you just went though was a whole lot of (potentially dangerous) work, for little benefit and saved very little cash. I’d rather pay for the dishes and save my time.
The lid makes up part of one yeah.
What’s potentially dangerous about reusable petris?
$10 isn’t a lot of money but 25 dishes aren’t going to go very far either. You’ll probably be ordering more in a few months. They run out at the worst times. They need special storage considerations since a sleeve can be damaged or opened by accident. If you do anything that might compromise the sterility of a disposable dish your only option is to throw it out or to risk using it anyway.
Cleaning out petris dishes is extremely easy as is sterilizing them.
Nothing is dangerous about reusable pp5 or glass petris (I was’t talking about your pp5 dishes, i use them), but lighting alcohol on fire in a SAB with a bottle of alcohol in there is pretty fucking silly to do in an attempt to reuse disposable petris as per the OPs “tek”. I edited my original post to make it easier to understand I wasn’t talking about the reusable petris (per Pastys tek, it’s the same tek I use). I think there was a little miscommunication on that Kizzle.
Edited by MrGiraffe (06/15/14 05:30 PM)
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Oh yeah, you’re talking about OP’s post
Obviously I wouldn’t do that. I didn’t even bother criticizing it. I think lighting plastic petris on fire to sterilize them speaks for itself
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…what about soaking in 95 percent ISO???…do any labs re sterilize them if you send them to them?
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…I’d much rather be fishing,!!!
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it would probably be cheaper to just but more than send them somewhere to br re sterilized. just use pp5’s/pasty plates if u want successful reuse of plates, or buy more if u using petris. i feel like any attempts at resterilizing the plastic petris would be too much of a hassle.
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A few thoughts on cultivation
MICROBIAL HUSBANDRY!!!!
The whole is greater than the sum of its parts
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…right-on…just a waste…
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…I’d much rather be fishing,!!!
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…what if you run a torch back and forth over them in front of a flow hood…if you keep it moving,it shouldn’t melt them-much…then dip in ISO,dry,and seal??
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…I’d much rather be fishing,!!!
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i still don’t get it?? petris are really cheap dude, order 100 of them for cheaper pricing (or 500 for even less). or use the pasty plate pp5’s for reusable. in the time it take to re sterilize them each, u could have poured a few sleeves.
u can always order the glass ones too, they are re usable and u PC them, but they slippery as shit in an SAB
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A few thoughts on cultivation
MICROBIAL HUSBANDRY!!!!
The whole is greater than the sum of its parts
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Quote:
BennD.42 said:
…what if you run a torch back and forth over them in front of a flow hood…if you keep it moving,it shouldn’t melt them-much…then dip in ISO,dry,and seal??
Seriously a blow torch over a .50 plastic disposable dish . Either roll with the pp5 plastics or invest in some glass petris.
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Quote:
blindingleaf said:
i still don’t get it?? petris are really cheap dude, order 100 of them for cheaper pricing (or 500 for even less). or use the pasty plate pp5’s for reusable. in the time it take to re sterilize them each, u could have poured a few sleeves.
u can always order the glass ones too, they are re usable and u PC them, but they slippery as shit in an SAB
What if you’re using rubber gloves as opposed to alcohol cleaned bare hands?
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well…im using alcohol cleaned gloves… shouldn’t we all be so lucky?
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A few thoughts on cultivation
MICROBIAL HUSBANDRY!!!!
The whole is greater than the sum of its parts
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Quote:
blindingleaf said:
well…im using alcohol cleaned gloves… shouldn’t we all be so lucky?
Ehh so slick as owl shit no matter what you do huh. I had a glove bag that came with thin plastic almost lunch lady type gloves, talk about slippery. When I started wearing vinyl medical gloves over top of those, stuff got a little easier to handle. I want to add some glass petris to the toolbox though, the pp5s are awesome (and cheap), but I want to feel like a mad scientist with all sorts of fancy glassware ahahah, nah but I like the thought of being able to use them for a long time as long as I take care of them.
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bodhisatta said:
Polystyrene dishes cannot be re sterilized except by gamma. Alcohol after heat sterilization is like putting shit on your body after showering. You can re sterilize glass andsome special expensive plastic dishes made of less clear plastic
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The goal of spiritual life is not altered states, but altered traits
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Polystyrene starts to warp above 90c which is hot enough to kill just about everything but endospores. Maybe you could get away with “sterilizing” it at 90 if you were also using antibiotic agar. But it’d make 100x more sense to just use a plate that doesn’t warp at sterilization temperatures if you want something you can reuse.
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…thanks fer every werd!!!…I’ll have to invest!,I’m starting my farm on cans n bottle money-and scrap metal money…just a few weeks away from 19 blocks ready to fruit…once they hitting the market-I’ll have some funds to play with!!!…
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…I’d much rather be fishing,!!!
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I t d o e s n ‘ t m a t t e r w h a t i t h i n k o f y o u . . . a l l t h a t m a t t e r s i s c l e a n s p a w n
I’m tired do me a favor
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to be clear, I’m not trying to make u feel down or discouraged dude…im just saying…if u trying to grow at first…do it right, if u trying to re invent the way we do culture storage….then have a field day…
if u growing shrooms, edible/active/medicinal, i will whole heartedly support it, no matter the procedure
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A few thoughts on cultivation
MICROBIAL HUSBANDRY!!!!
The whole is greater than the sum of its parts
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I’ve always wondered why nobody doesn’t just wash their used petri dishes in soapy water
and rinse them in cold water to remove the soap. Then afterwards soak the petri dishes in
30% hydrogen peroxide overnight. That stuff will kill anything.
I’m not sure if anything can live exposed
to 30% hydrogen peroxide for more than a
few minutes let alone an overnight soak.
What do you guys think?
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Peroxide certainly doesn’t kill everything, in fact it pretty much useless on most of the ones we’re concerned about. If you ever wondered what that bubbling is when you put it on something, that’s the organisms instantly breaking it down into harmless oxygen and water.
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just use pasty plates mindblowing how complicated people try to make things
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PussyFart said:
Quote:
spore baby said:
I’ve always wondered why nobody doesn’t just wash their used petri dishes in soapy water
and rinse them in cold water to remove the soap. Then afterwards soak the petri dishes in
30% hydrogen peroxide overnight. That stuff will kill anything.
Try it and let us know how it turns out.
This fall when I start up again I will and will post it.
At least, I think it’s a valid idea.
I poured some 30% hydrogen peroxide once on peat moss
and you could hear and smell the burning. I don’t think the
bacteria in there lived.
I just hope the plastic petri dishes don’t melt.
I’ll let you all know how it goes.
Maybe, somebody will try it before me.
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Quote:
Kizzle said:
Peroxide certainly doesn’t kill everything, in fact it pretty much useless on most of the ones we’re concerned about. If you ever wondered what that bubbling is when you put it on something, that’s the organisms instantly breaking it down into harmless oxygen and water.
In acidic solutions, Hydrogen peroxide is one of the most powerful oxidizers known—stronger than chlorine, chlorine dioxide, and potassium permanganate.
http://en.wikipedia.org/wiki/Hyd rogen_peroxide
I’m not talking a 3% solution.
Get some 30% hydrogen peroxide and pour that on any bacteria slime and see if it lives. I don’t think it will.
Edited by spore baby (07/31/14 01:33 AM)
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Hydrogen peroxide doesn’t come in 30%, at least not at any store I’m aware of. You’d have to order it. In which case you might as well just order more petris.
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PussyFart said:
You could buy a case of 500 petris for the same price as 500ml of 30% hydrogen peroxide…..is it really worth it?
I can get 29% hydrogen peroxide at my local hydroponic store.
Look this is a store in my city.
It’s listed as O2 but take my word it’s hydrogen peroxide.
O2 29% 1L $14.95. I’m pretty sure 500 petri dishes cost a whole lot more than that.
http://www.greenandclean.ca/hydr oponic-products/ec-ph-testing-wat er-treatment/
Actually you can get quite a few nice chemicals at a hydroponic store.
I can get 85% phosphoric acid at mine, potassium hydroxide, dilute nitric acid,etc.
Go check out one near you and you may see something nice.
Edited by spore baby (07/31/14 03:54 AM)
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That’s overkill. Anything ACS is too much $$$.
Look at mine 1 liter of 29% for $14,95 Canadian
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Quote:
tombosley8 said:
just use pasty plates mindblowing how complicated people try to make things
Pasty plates are awesome, and serve a purpose, but eventually you’re going to want to get some legit petris and learn how to pour. The visibility is way better with legit petris. I’m pretty sure Pasty himself uses mainly petris now. Pasty plates were my first adventure into agar, and I still try to use them when I put known contaminated tissue (such as from wild collected mushrooms), no need in wasting a disposable if I know it’s contaminated. AFter the 2nd or 3rd transfer, then I put it to a disposable petri.
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For the sake of arguments, let’s say you can sterilize petris with peroxide.
How would you do it? You would need to soak them in a sterile container in a sterile environment and maintain sterility while putting them in a sterile storage container. Seems like a lot of effort for little, if any, reward.
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The Basics
A little civility goes a long way
The Noob Forum
The Hammock Hangers’ Forum
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Yeah, but the ability to sterilize petri dishes would be nice at times.
For example: When you need some for expanding your cultures and run out.
Mycelium grows faster than the mail man can deliver.
I’m not saying it’s an end all. I’m just saying it would be nice
to have an option for those times when your supplies run low.
I imagine having a small tub with a lid inside
a glove box with the peroxide solution would
work fine.
Oh yeah, anyone of you see the 99% hydrogen peroxide video yet?
You can start fires with it. I need to get some. Talk about flame sterilizing.
Just watch what it does to leather,sugar and flour.
Edited by spore baby (07/31/14 09:56 AM)
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Quote:
Yeah, but the ability to sterilize petri dishes would be nice at times.
That’s why they have glass petri dishes. They can pressure cooked or oven sterilized.
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Yeah, those are sure really nice.
I will get a dozen of those pyrex petri dishes someday.
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yup, I thought my tek where you just throw them on the fire was best for sterilizing petris.
edit: dammit there was loads of posts in between… the one I was referring to said it was more effort than it was worth.
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T h e n e a r e s t w e e v e r c o m e t o k n o w i n g t r u t h i s w h e n w e a r e w i t n e s s t o p a r a d o x .
Edited by Northerner (08/01/14 01:58 AM)
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Spore baby, ever get around to those experiments?
Also, does anyone know if the pyrex petri dishes have tighter tolerances than the cheaper flint glass ones? That’s my main issue with the glass dishes… I worry that the larger opening leaves them more susceptible to contamination. Not to mention that sometimes the parafilm cracks without me noticing it until I see a fruit fly munching down in there.
This supports your hypothesis to some degree:
“Vaporized Hydrogen Peroxide (VHP®). Hydrogen peroxide solutions have been used as chemical sterilants for many years. However, the VHP® was not developed for the sterilization of medical equipment until the mid-1980s. One method for delivering VHP to the reaction site uses a deep vacuum to pull liquid hydrogen peroxide (30-35% concentration) from a disposable cartridge through a heated vaporizer and then, following vaporization, into the sterilization chamber. A second approach to VHP delivery is the flow-through approach in which the VHP is carried into the sterilization chamber by a carrier gas such as air using either a slight negative pressure (vacuum) or slight positive pressure. Applications of this technology include vacuum systems for industrial sterilization of medical devices and atmospheric systems for decontaminating for large and small areas853. VHP offers several appealing features that include rapid cycle time (e.g., 30-45 minutes); low temperature; environmentally safe by-products (H2O, oxygen [O2]); good material compatibility; and ease of operation, installation and monitoring. VHP has limitations including that cellulose cannot be processed; nylon becomes brittle; and VHP penetration capabilities are less than those of ETO. VHP has not been cleared by FDA for sterilization of medical devices in healthcare facilities.
The feasibility of utilizing vapor-phase hydrogen peroxide as a surface decontaminant and sterilizer was evaluated in a centrifuge decontamination application. In this study, vapor-phase hydrogen peroxide was shown to possess significant sporicidal activity 941. In preliminary studies, hydrogen peroxide vapor decontamination has been found to be a highly effective method of eradicating MRSA, Serratia marcescens, Clostridium botulinum spores and Clostridium difficile from rooms, furniture, surfaces and/or equipment; however, further investigation of this method to demonstrate both safety and effectiveness in reducing infection rates are required942-945.”
However I found this to be more interesting:
“Ozone. Ozone has been used for years as a drinking water disinfectant. Ozone is produced when O2 is energized and split into two monatomic (O1) molecules. The monatomic oxygen molecules then collide with O2 molecules to form ozone, which is O3. Thus, ozone consists of O2 with a loosely bonded third oxygen atom that is readily available to attach to, and oxidize, other molecules. This additional oxygen atom makes ozone a powerful oxidant that destroys microorganisms but is highly unstable (i.e., half-life of 22 minutes at room temperature).
A new sterilization process, which uses ozone as the sterilant, was cleared by FDA in August 2003 for processing reusable medical devices. The sterilizer creates its own sterilant internally from USP grade oxygen, steam-quality water and electricity; the sterilant is converted back to oxygen and water vapor at the end of the cycle by a passing through a catalyst before being exhausted into the room. The duration of the sterilization cycle is about 4 h and 15 m, and it occurs at 30-35oC. Microbial efficacy has been demonstrated by achieving a SAL of 10-6 with a variety of microorganisms to include the most resistant microorganism, Geobacillus stearothermophilus.
The ozone process is compatible with a wide range of commonly used materials including stainless steel, titanium, anodized aluminum, ceramic, glass, silica, PVC, Teflon, silicone, polypropylene, polyethylene and acrylic. In addition, rigid lumen devices of the following diameter and length can be processed: internal diameter (ID): > 2 mm, length ≤ 25 cm; ID > 3 mm, length ≤ 47 cm; and ID > 4 mm, length ≤ 60 cm.
The process should be safe for use by the operator because there is no handling of the sterilant, no toxic emissions, no residue to aerate, and low operating temperature means there is no danger of an accidental burn. The cycle is monitored using a self-contained biological indicator and a chemical indicator. The sterilization chamber is small, about 4 ft3 (Written communication, S Dufresne, July 2004).
A gaseous ozone generator was investigated for decontamination of rooms used to house patients colonized with MRSA. The results demonstrated that the device tested would be inadequate for the decontamination of a hospital room946.”
http://www.cdc.gov/hicpac/disinf ection_sterilization/13_10otherst erilizationmethods.html
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Chris893 Trade List <-- click to see what I have for trade Looking for <-- click to see if you have something I want Extras: Top Quote: Also, does anyone know if the pyrex petri dishes have tighter tolerances than the cheaper flint glass ones? That's my main issue with the glass dishes... I worry that the larger opening leaves them more susceptible to contamination. Not to mention that sometimes the parafilm cracks without me noticing it until I see a fruit fly munching down in there. Some are like that intentionally it's not just because they're cheap. You can find others though, just look at what you're getting before you buy it. Look for ones with beaded edges. Edited by Kizzle (10/14/14 07:28 PM) Extras: Top Thanks, I'll look around. I usually get my glass petris as well as culture tubes from cynmar. Their prices and shipping are pretty competitive, no beaded dishes though. -------------------- Chris893 Trade List <-- click to see what I have for trade Looking for <-- click to see if you have something I want Extras: Top wow... 4 pages before we realized this post was absolute trash in this community. If you need to reuse plastic petri dishes, you need change hobbies. Besides, who doesn't have jars kicking around? Or cups? OR PP5 lunch containers? jesus... Extras: Top Quote: SpitballJedi said: I notice the parafilm doesn't crack nearly as much if I put the petri in a ziplock while colonizing and/or don't over stretch it. I was hoping it wouldn't come to that. I'm going to try not stacking them to see if that is a contributing factor, making weak spots when they stick to one another. But, if it is just because of drying out or temperature changes, then I'll definitely be using the bags. Kizzle, Can you upload a pic showing what you are talking about? When I look them up I can't tell the difference, I just see petri dishes. -------------------- Chris893 Trade List <-- click to see what I have for trade Looking for <-- click to see if you have something I want Extras: Top You can see how the glass sort of bulges out at the rim. That can help center it so the lid slide around as much when they're closed. There'll always some kind of gap on the sides though. It's meant to reduce contamination and make them easier to open and close quickly because the sides aren't scraping together when you put the lid on. -------------------- Extras: Top It's not like they take a lot of PC space. What's with people washing dishes when plastic forks and paper plates are so cheap? -------------------- Extras: Top Quote: RogerRabbit said: All this to save 25 cents, which is the most I've ever paid for pre-sterilized petri dishes. RR where do you buy your pre-sterilized petri dishes? Extras: Top Quote: dehingoli said: I know its not practical but I got myself in a situation where I got stuck with plastic petris and had no choice but to experiment. here's what i did so far. what i used: 12 used petri dishes with the opened plastic bag/wrap that came with it. 95% isopropyl alcohol bic lighter dinner plate allot of napkins/ paper towels microwave a. clean open the lid of the petri dishes and pour some h2o2 over the used up agar. close lid. wait for bubbles to subside. open the lid and remove the agar from the petri dish. i used a butter knife to lift the sides then throw them in the garbage. dispose agar properly in a closed plastic bag. (or incinerate/ dump in hot water) b. soak put water bleach solution in a container large enough to fit the petri dishes. also make sure the water is warm enough but not too hot to melt the plastic. i used "almost" boiling water and added some normal temp water to control the heat. soak empty petri dishes in a container with water bleach solution. make sure the petri dishes are separated from the top and bottom parts. and make sure you have enough water/bleach to cover the petri dishes. cover container to maintain temp until water comes to room temp. drain water from container and rinse petri dishes with a wash of lukewarm water to remove soap, suds or excessive bleach. drain lukewarm water and get ready to assemble dishes. c. re assembly/ drying put the petri dishes back together while using a cotton ball dabbed in some alcohol (not too wet, just enough to sanitize) to dry the inside parts of the petri dishes. (i prefer to do this in still air) i wipe the petri dishes' inside part facing down as to be careful not to expose the inside to falling contaminants (if that makes sense?). close petri dishes right after you dry the inside with cotton. stack them up nicely and from this point on, we will be calling this "the left stack" d. alcohol blasting this is the tricky part. you would need high 95% alcohol or higher. the prep: prepping is key as i stack them at a manageable height, i put them on my left side so i can use my left hand to bring the petri dishes over to my middle where my alcohol sanitized dinner plate is (this is where we will do the blasting). i also make sure that i have space to my right where i can stack them after i alcohol blast them. put the alcohol in a clean container where a syringe can be loaded in place and suck some alcohol in. for visual pusposes i shall name the objects in this process left stack: this stack is where you will be getting your petri dishes FROM middle: this is where you will transfer petri dishes one plate at a time and do the blasting right stack:from the middle stack, this is where you will be moving the petri dishes TO here is the diagram: [image] [/image] lets do this: using left hand, get one petri from left stack and place the in the middle plate. with your right hand,get the alcohol loaded syringe and point it to the inside part of the petri while you slightly lift the cover from the petri dish. lift cover just enough to spray alcohol inside to put enough alcohol(doing it just like innoculating lc to agar). no need to spray all over insides as next step will cover that. close the lid. after the lid is closed, shake the petri dish so that the alcohol will uniformly be coating the inside. excess alcohol can be drained from the sides of the petri dish. just tilt it so you can remove excess alcohol. wipe the outside with alcohol dabbed clean cotton and remove excess alcohol. wipe the plate dry as well and then, put the petri dish back at the middle plate. now... get a bic lighter.. you know where im getting at here? this stuff needs more practice than any of the things weve done here so far. same motion as innoculating lc to agar, but this time well blow things up. for those who do not know, this will create a small gas explosion as we light up the lighter next to a semi opened petri dish cover. so... using your left hand, lift the cover enough for an gap to light the gas inside with a lighter on your right hand. be aware that after the explosion, you have a millisecond the put the flame out by replacing the lid to cut air and kill the flame. the longer you kill the flame with the lid, the more chances of you melting your PLASTIC PETRI dish. as a tip i would advice to lift te cover slightly but still close enough to make sure that when you release the cover, it sill still fall alligned to the bottom dish therefore shutting it without aiming. i used my ears more for this drill as when i hear the poof, i release the cover and shutting it.. once done, move the blasted perti to the right stack. REPEAT until finished. e. microwave drying now you have your right stack, hopefully your left with a most of your plastic petris intact. ( i lost 2 out of 12) if you still have the plastic sleeve/ container of your plastic petris i would put them back now but i suggest you put a layer of clean/ sterile cloth in between the plastic container and the petri dish. assuming that you follow how the others do it, you should end up with the open side of the plastic bag at the bottom and the sealed part at the tom part of the stack. now place it inside the microwave, make sure the plastic open side is facing up (top side down). you want to do this so the hot gases escape while we heat the petris. heat at medium until no more water is visible inside the petris. id suggest you open the mocrowave and check on your petris every now and the to monitor heat build up. VOILA. next logical step is to fill it with weak peroxide/agar solution. will post pics soon. You should just put them in the microwave for 45 minutes. Extras: Top I think they would melt in the micro for that long. Just keep plenty of fresh petris to spare and the problems solved. Quote: PussyFart said: Quote: BLMP5 said: where do you buy your pre-sterilized petri dishes? ebay by the case Great advice.... still I enjoy prepour much better than petris Pastyplates for the win. -------------------- Extras: Top This is what i found in a website Sterilizing Plastic Petri Dishes Mix 1/2 cup of Clorox (any 10 percent bleach solution will work) with 4 1/2 cups of warm tap water. You can mix more or less of the sterilization solution by remembering it one part bleach to nine parts water. Set the mixture aside. Using a soft, non-abrasive cloth, antibacterial dish soap and warm water, gently clean and rinse the plastic Petri dishes. The Petri dishes should be free of all debris, including any soap residue. Place the Petri dishes into the sterile bleach solution, one at a time, for approximately two minutes each. Using sterile lab tongs, remove the Petri dish from the solution. Allow it to air drip for a few seconds; place it in a bowl of rubbing alcohol. Immediately remove the Petri dish from the rubbing alcohol with another pair of sterile lab tongs and place it on a sanitary surface to air dry. Store the sterilized Petri dishes in a sterile area until next use. Extras: Top Two minutes is a surprisingly short time. I would also suggest not mixing unknown disinfectants, so just use plain dish soap. (It's also not a proper tek if it can't say which antibacterial soap to use.) Using alcohol is clever, since that will both rinse it and help it dry, and that's actually harder than just disinfecting with chemicals. Last, I would use acidified dilute bleach (pH: 5-7) rather than just dilute bleach. More hypochlorous acid, less hypochlorite. I haven't tried any of this, though. I will do this if I can ever convince myself that I don't hate cleaning. Extras: Top
US4417926A – Method for cleaning and disinfecting used plastic Petri dishes – Google Patents
BACKGROUND OF THE INVENTION
1. Field of the Invention:
This invention relates to a method and apparatus for the rendering harmless and cleaning of infectious plastic waste material, namely, used Petri dishes made of plastic. In this context, the term “rendering harmless” is to be construed as meaning “disinfection”, i.e. killing pathogenic organisms to the extent required for practical purposes.
2. Prior Art:
Petri dishes are shallow round flat-bottomed dishes of transparent material which are used for microbiological culture processes, e.g. for culturing specimens of bacteria or other microorganisms. The microorganisms are cultured on a substrate which may be in the form of sterilized agar-agar that has been heated and poured into the dish and allowed to solidify therein to form a solid flat plate; the agar-filled Petri dishes are commonly referred to as agar plates. After the specimen to be cultured has been applied to the substrate, a close-fitting lid is placed on the agar plate which is then inserted in an incubator where a controlled atmosphere is maintained. When the culturing process is completed, the cultured specimen is examined while still on the substrate.
Present-day Petri dishes are almost always produced by injection molding of plastic (clear polystyrene) and used as a disposable article. It is presumed herein that the Petri dishes are made of plastic.
Since the cultured specimens may be pathogenic, the used agar plates must be handled such that the danger of transmission of infection is minimized. The handling therefore is rather laborious. Most microbiological laboratories consume large quantities of agar plates and in some laboratories the disposal of used agar plates is more or less a full-time occupation of one person.
The disposal of used agar plates often comprises collection of the lid-bearing agar plates in bags which are closed and placed in an autoclave in which the bag is subjected to a high temperature (well above 100° C.) at elevated pressure. The bag with the now hopefully disinfected agar plates then is carried away to a refuse incinerating installation where it is burned. This way of disposing of the used agar plates not only is laborious and energy-consuming, but also leads to air pollution and destruction of valuable reusable plastic material.
SUMMARY OF THE INVENTION
The principal object of the invention is to improve the disposal of used agar plates and at the same time provide a possibility to recycle the plastic material. The problem to be solved thus is to render pathogenic organisms in or on the agar plates harmless without decomposing or otherwise destroying the plastic material and to remove the culture substrate and specimen residues.
In accordance with the invention, the agar plates are rendered harmless by heating to a temperature that is sufficient to bring about disinfection. However, in contrast to the prior art techniques, the agar plates are heated in water or other suitable fluid at a temperature below the boiling point and substantially at atmospheric pressure. In a preferred embodiment the heating serves not only to bring about disinfection and cleaning without destruction of the plastic, but also to bring about a desired but random, i.e. uncontrolled, distortion of the agar plates, including the lids, so that the interior becomes freely exposed to the water, and to liquefy the substrate (agar-agar and any added nutrient substance).
The preferred embodiment thus includes taking advantage of mechanical stresses which are accidentally or deliberately introduced in the Petri dishes during their manufacture to cause the agar plates to open themselves and thereby provide unobstructed access for the water to the interior of the agar plates so that the water can reliably effect the disinfection and the liquefaction of the culture substrate and so that the liquefied substrate can readily be washed out of the agar plates.
Heating to a temperature of about 90° C.–and sometimes even heating to only about 80° C.–is sufficient in practice (this temperature of course has to be maintained for a certain period of time to ensure killing of the pathogenic organisms to a sufficient extent), and the heating therefore can be effected in water and at atmospheric pressure. The used agar plates thus may be placed in a vessel with their lids still on and subjected to the action of hot water, preferably under agitation, for a predetermined time that is sufficient to bring about disinfection (the time is dependent on the temperature). After that, the water is drained off together with the liquefied substrate–the water may be passed into the public sewage system–and the disinfected and cleaned agar plates may then be kept and recycled without any particular measures being necessary to prevent transmission of infection.
It is preferred in carrying the invention into effect to handle the used agar plates in batches. In accordance with a preferred embodiment of the method of the invention, the used agar plates are collected in a bag which is made at least partially of a material that is solid at room temperature but soluble in water at the disinfection temperature. When the bag has been filled, it is placed in the heating vessel and subjected to the action of the hot water which thus dissolves or at least opens the bag and thus can contact the agar plates.
Available on the market are various materials which may be used for bags and which have the above-mentioned properties. One example of such a material is the plastic sheet or film material sold under the designation Kuraray Poval Film (polyvinyl alcohol film) by Kuraray Co. Ltd., Kurashiki-City, Japan, and recommended for use e.g. as a mold release agent and as a food or textile packaging material. This material is rapidly dissolved in hot water and may be allowed to go into the public sewage system.
In the above-mentioned preferred embodiment, the used agar plates may be collected in bags of a suitable size which are made wholly or partly of a material having the aforesaid properties and which are thus dissolved or at least opened when heated in water. As the bags become filled with the used agar plates, they are closed or sealed. They may then either be stored, pending transfer to the heating vessel, or immediately placed in the heating vessel to be stored there until the vessel has been filled with bags. The manual handling of the used, unprotected agar plate thereby is limited to the transit from the place of examination to the bag. The bag may suitably be small enough to make it convenient to have it at or near the place of examination so that the person making the examination can directly throw the agar plates into the bag upon completion of the examination. Thereby the danger of transmission of infection is minimized.
The method of the invention and an apparatus for carrying it into effect are described hereinafter with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagrammatic view in axial cross section of a disinfecting and cleaning apparatus embodying the invention;
FIG. 2 is a cross-sectional view taken on line II–II of FIG. 1.
DETAILED DESCRIPTION
In carrying out disinfection and cleaning of used agar plates by means of the illustrated apparatus, the used agar plates are collected in bags of the afore-mentioned kind with, say, about 100 agar plates in each bag. The apparatus may be dimensioned for simultaneous disinfection and cleaning of about 400 agar plates, corresponding to four bags with 100 agar plates each. Before the filled bags are transferred to and loaded into the apparatus, they have been closed in a suitable manner, preferably through sealing or by means of a closure device made of the same water-soluble material as the bags.
The apparatus comprises a perforated cylindrical drum 10 journalled for rotation about a horizontal axis in a heating vessel 12 which is hereinafter referred to as a “housing”. The housing is adapted to be closed in a bacterium-tight manner so that any bacteria present within the housing cannot escape therefrom into the surrounding atmosphere. However, even when the housing is closed, fluid communication between the interior of the housing and the surrounding atmosphere may take place by way of a bacterial filter 11. A frame 13 encloses the housing 12 and also has a charging and discharging door 14, an electric drum drive motor 15, water supply and discharge conduits 16 and 17, respectively, provided with suitable valves, as well as other elements, some of which are referred to hereinafter and some of which are omitted both from the drawings and the following description because they are not believed to be relevant to the invention.
The drum 10 is open over the entire cross-section at one end, and at the other end is secured to a shaft 18 which is rotatably supported by the housing 12 and connected with the motor 15 through a belt transmission 15A. At the point where the shaft 18 is passed through the vertical rear wall of the housing 12 and journalled in a bearing sleeve 18A attached to the housing, a seal 18B is provided to prevent water from leaking from the housing along the shaft. Moreover, means (not shown) are provided adjacent the seal which serve to lead any water accidentally leaking past the seal into a separate collecting vessel. The water may be infectious and therefore must not be allowed to escape in an uncontrolled manner from the housing. Presence of water in the collecting vessel signals that the seal is faulty and should be replaced or repaired. The circumferential wall of the drum 10 is perforated to permit virtually unrestricted fluid communication between the interior of the drum and the surrounding regions of the housing but retain the agar plates within the drum.
As shown in FIG. 1, the front wall of the housing 12 is provided with an opening in front of the open end of the drum 10. This opening, which can be closed in bacterium-tight manner by the door 14, is somewhat larger than the open end of the drum. When the door is open, the drum is thus accessible over the entire cross-section thereof to facilitate the insertion of the filled bags. The bags are shown in phantom lines at 19.
Below the drum 10, the space between the housing 12 and the circumferential wall of the drum has an enlarged region 12A in which an electrical heater 20 is provided. The water supply conduit 16, which includes a solenoid valve 16A, opens into the enlarged region 12A. The water discharge conduit 17, which likewise includes a solenoid valve 17A, is connected to the enlarged region 12A through the bottom wall of the housing. Moreover, the enlarged region houses a coiled metal tube (not shown) extending between the journal sleeve 18A and the afore-mentioned vessel for collecting any leaking water.
The operation of the disinfection and cleaning apparatus is controlled by a device that has been omitted from the drawings in the interest of clarity and is monitored by means of various safety devices which are also omitted for the just-mentioned reason.
After the bags 19 have been placed in the drum 10, the door 14 is closed whereupon the disinfection and cleaning process may be initiated. Initially, the housing 12 is filled with cold or preheated water up to a predetermined level. The water is then heated to a predetermined set temperature, e.g. 90° C., by means of the heater 20 and maintained at that temperature for a predetermined time, e.g. 30 minutes, sufficient to ensure disinfection. During this time, and possibly also during the filling of the housing with water, the drum 10 is rotated slowly in one direction by the motor 15 to cause the agar plates to tumble.
When the temperature of the water has been raised to 40°-80° C., the water dissolves the water-soluble bag material and contacts the agar plates. The consequent heating of the agar plates in many cases leads to a considerable and irregular distortion of the agar plates so that large openings are formed between the agar plates and their lids to give the water virtually unobstructed access to the interior of the agar plates. The rotation of the drum and the resulting agitation also assist in bringing the hot water into contact with every part of the agar plates. The agar substrate is melted and mixed with the water together with the residues of the cultured specimens and the dissolved bag material.
When the predetermined time has elapsed, the agar plates are washed free of the substrate and the pathogenic organisms are killed to the required extent. A predetermined quantity of additional water is then fed into the housing to lower the agar concentration and improve the washing. After a brief period of continued agitation of the agar plates and the water, the water is drained off through the discharge conduit 17 and led to the public sewage system. The rotation of the drum is continued during the draining off of the water to continue the tumbling of the now cleaned agar plates and thereby ensure that the agar plates are completely emptied of water. When the water has been drained off, pure water is again fed into the housing and the drum is rotated to ensure a thorough additional rinsing of the agar plates. The rinsing water, which need not necessarily be heated, is then drained off while the rotation of the drum is continued.
The agar plates are now rendered harmless and freed of the agar substrate. Accordingly, the door 14 may safely be opened so that the agar plates can be removed from the drum 10. The removal is effected by rotating the drum in the opposite direction. An inclined ridge 10A on the inner side of the circumferential wall of the drum assists in feeding the agar plates through the open end of the drum into a chute 22 positioned beneath the door leading to a bin 21. Alternatively, the agar plates may be discharged into a feed hopper of a mill in which they are comminuted. The now cleaned plastic material may be reused.
If the agar plates are not sufficiently clean after the above-described treatment, e.g. in view of requirements for cleanliness that have to be met to permit recycling of the plastic material, the above-mentioned rinsing step may be followed by one or more additional rinsings with cold or hot water.
The drawings show the preferred embodiment of the disinfection and cleaning apparatus. However, other embodiments are also within the scope of the invention. For example, although the illustrated horizontal disposition of the drum is believed to be preferable, it is also possible to journal the drum for rotation about a vertical axis and charge and discharge the agar plates through the top end of the drum. It may also be possible to effect agitation of the agar plates and the water in the drum in ways other than by rotating the drum.
The bacterial filter 11 may be of any suitable type available on the market. After the door 14 has been closed and sealingly engages the frame 13, the only path of fluid communication between the interior of the housing 12 and the surrounding atmosphere is formed by the bacterial filter 11. The bacterial filter 11 permits air and steam to pass relatively freely from the housing to the surrounding atmosphere but forms a barrier to bacteria. Hence, the bacterial filter 11 ensures that the interior of the housing 12 is always substantially at atmospheric pressure. The filter 11 has very fine pores and may therefore be unable to always prevent a certain overpressure to develop inside the housing as a result of the heating, but such overpressure is very small and need hardly be taken into consideration when designing the apparatus. It is proper, therefore, to regard the pressure differential between the interior of the drum and the surrounding atmosphere as a substantially zero pressure differential.
The temperature of the water should be as high as possible during the disinfection, i.e. as close to 100° C. as possible. At the same time, however, boiling of the water has to be avoided, and as a practical matter the temperature has to be kept slightly below 100° C., suitably between 90° C. and about 98° C. In the illustrated embodiment, a temperature control device (not shown) is set to keep the temperature at 95° C. so that an adequate margin to the boiling point exists. A temperature sensor (not shown) provides a warning signal if during the disinfection step the temperature should drop below the preferred lower temperature limit of 90° C.
Some types or makes of plastic Petri dishes do not have as marked a tendency as others to distort when heated in accordance with the invention. The distortion is caused by the relieving of internal stresses in the plastic material resulting from the heating. These stresses are brought about during the die-casting of the Petri dishes as the plastic material solidifies in the mold. During the actual use of the Petri dishes, the stresses are not harmful. It is therefore possible in those cases where sufficient stresses are not brought about anyway to modify the production process such that sufficiently heavy stresses are built into the Petri dishes to effect the desired distortion when the method of the invention is carried out. However, although the distortion of the agar plates is very advantageous, absence of distortion need not mean that the disinfection and cleaning will be insufficient.
Although the bags in which the used agar plates are collected may consist exclusively of a material that is soluble in hot water, it is within the scope of the invention to use bags which only partially consist of such a material. For example, the bags may be made largely of insoluble material but be provided with seams and/or closures which are dissolved by the hot water to open the bags. After completed treatment of the agar plates within the housing, the undissolved bag material can readily be separated from the disinfected and cleaned agar plates if desired or required.
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