Sterilising agar without autoclave?

Is there a way of sterilising agar without using an autoclave or pressure cooker? We don't have the funds for an autoclave and no hob to use the pressure cooker.

I read on a website:
"(a) By a single exposure at 100°C for 90 minutes.

(b) By intermittent exposure at 100°C for 20-45 minutes on each three successive days.

(a) Single exposure at 100°C for 90 minutes-is not suitable as the spores of thermophilic and some mesophilic bacteria can survive this exposure.

(b) Intermittent exposure at 100°C for 20-45 minutes for three successive days is also known as “Tyndallisation“. In this method one exposure will destroy all the vegetative organisms between the heating’s, the spores in favourable nutrient medium become vegetative forms which are killed during the subsequent heating."

would this be a suitable method for sterilising agar?

Thanks
 
I haven't come across that method so I do not know if it is suitable. My question would be, What are you using the agar plates for? If this is for microbiology, then without an autoclave or pressure cooker how will you dispose of the waste afterwards? I would suggest purchasing a pressure cooker and electric hot plate/stove to heat it on. It will save you a lot of time and effort, especially if the alternative involves three successive days of heating.
 
Yes it would be for microbiology. I had assumed if that was suitable to sterilise the agar the same method could be used for disposal. The hot plate and pressure cooker seems like a good idea. My head of department is reluctant to get a pressure cooker because of the added H&S concerns but I'll suggest it to him again. Thanks
 
Yes it would be for microbiology. I had assumed if that was suitable to sterilise the agar the same method could be used for disposal. The hot plate and pressure cooker seems like a good idea. My head of department is reluctant to get a pressure cooker because of the added H&S concerns but I'll suggest it to him again. Thanks
I think it will make your life much easier to have one, though you do need to bear in mind that pressure vessels need to be serviced annually. We buy a new pressure cooker each year, as it is probably cheaper than getting someone in to service it. If you get one, go for a high dome one, as I ordered a regular one by accident one year and struggled to put my agar bottles in.
 
Let us know if you find out. Does it refer to putting something in an oven to maintain that temperature? I think the three days sterilising followed by three days for disposal would be enough to put me off.
 

CovTech

Lvl 37 Alchemist
COMMITTEE
CLEAPSS has two ways of sterilising nearly all liquids for microbiology:
  • Wet Sterilising - 121 degrees at 15PSI for 15mins with steam (pressure cooker)
  • Dry Steriising - 160°C for 2 hours or 180°C for 35 minutes (oven)
Can't see them going for anything else (assuming you're a CLEAPSS member)
 
CLEAPSS has two ways of sterilising nearly all liquids for microbiology:
  • Wet Sterilising - 121 degrees at 15PSI for 15mins with steam (pressure cooker)
  • Dry Steriising - 160°C for 2 hours or 180°C for 35 minutes (oven)
Can't see them going for anything else (assuming you're a CLEAPSS member)
I'm not sure Food Tech would be happy with me sticking my bacterial plates in their oven either.
 
Is there a way of sterilising agar without using an autoclave or pressure cooker? We don't have the funds for an autoclave and no hob to use the pressure cooker.

I read on a website:
"(a) By a single exposure at 100°C for 90 minutes.

(b) By intermittent exposure at 100°C for 20-45 minutes on each three successive days.

(a) Single exposure at 100°C for 90 minutes-is not suitable as the spores of thermophilic and some mesophilic bacteria can survive this exposure.

(b) Intermittent exposure at 100°C for 20-45 minutes for three successive days is also known as “Tyndallisation“. In this method one exposure will destroy all the vegetative organisms between the heating’s, the spores in favourable nutrient medium become vegetative forms which are killed during the subsequent heating."

would this be a suitable method for sterilising agar?

Thanks
Then you don't do microbiology practicals I assume?
 
I certainly wouldn't advise intermittent exposure as that would seem to be a recipe for producing some thermophillic strains... CLEAPSS advise suggests a higher temperature is needed to kill stuff off too.
I'm not sure Food Tech would be happy with me sticking my bacterial plates in their oven either.
The canteen here wouldn't either - they have their own strains to look after in there...
 
For the cheapest, easiest option, you need a pressure cooker. Cleapss only recommend the Prestige 5L High Dome. No pressure cooker, no practicals. You will need a WSE if you carry on using it after a year. I used a company called Mandate Systems who provided an annual WSE for around £25.

A hotplate is the safest way to heat it but make sure it is a good one. I had a cheap one that would not raise the pressure enough for the valve to raise! Ended up resorting to Bunsen burners and tripods which is less than ideal!
 
Is there a way of sterilising agar without using an autoclave or pressure cooker? We don't have the funds for an autoclave and no hob to use the pressure cooker.

I read on a website:
"(a) By a single exposure at 100°C for 90 minutes.

(b) By intermittent exposure at 100°C for 20-45 minutes on each three successive days.

(a) Single exposure at 100°C for 90 minutes-is not suitable as the spores of thermophilic and some mesophilic bacteria can survive this exposure.

(b) Intermittent exposure at 100°C for 20-45 minutes for three successive days is also known as “Tyndallisation“. In this method one exposure will destroy all the vegetative organisms between the heating’s, the spores in favourable nutrient medium become vegetative forms which are killed during the subsequent heating."

would this be a suitable method for sterilising agar?

Thanks
To sterilise agar you need the working temperature to be 121 degrees which can only be achieved by using a pressure cooker. You can buy a single electric hotplate below for £11.95 on Amazon


The pressure cooker is around £52. My thoughts are that if the school cannot buy this then maybe you tube videos are best. There are some agars which are specific to certain bacteria that only need boiling. Having worked in a micro lab for some years we only used one such agar for (VRBNA) which if I recall correctly was for enterobacter. Seems a shame to not do this topic properly
 
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