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Using UV light for sterilization


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#21 Needles

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Posted 25 March 2016 - 11:33 AM

so I mounted the UV lamp from the EPROM eraser into my flow hood. I don't know why I wanted to mount the controls for it on the front of this thing. Would have been so much easier just to move the bulb. Especially if it doesn't work. My main concern is with the concentration of the light and the distance to the work area.
I took the flow hood for a test drive and just used isopropyl alcohol to sanitize the inner surface. So far no contamination on any plates.
To test the UV light I am starting with molds. Once I have a culture plate growing out I will expose new plates inoculated with mold spores to various time levels of UV exposure and see if anything grows.
image.jpeg image.jpeg image.jpeg

#22 Needles

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Posted 29 March 2016 - 07:06 PM

Now it's time to see if the UV light out of a EPROM eraser will prevent mold spores from germinating. From this plateimage.jpeg I looped and inoculated four plates of PDA and exposed three plates to UV light. One received no exposure the others at ten, twenty and thirty minuets. image.jpeg image.jpeg We're leaving town for work and will return next Sunday. By then the results should be in.
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#23 GadgetGuy

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Posted 29 March 2016 - 08:42 PM

Sweet!



#24 Needles

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Posted 30 March 2016 - 11:13 AM

No need to wait until Sunday. All four plates are showing some contamination. The 30 minute plate is showing less then the others but still infected. I can't say if it's just a old bulb or to far from the work area maybe just not enough time idk. It was a good experiment that wasn't to much of a loss. The flow hood works fine without it so still good to go. If I ever try something new with UV I'll bump this thread. .....

#25 Needles

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Posted 13 April 2016 - 10:15 AM

Found a interesting result yesterday as I was working with bactiria. I was doing some live mount micrographic studies and wondered about the effects of the UV light on living bactiria. After positioning the slide six inches from the uv light for fifteen minutes of exposure I checked the sample under the microscope. There was no movement by any bactiria cells. Although my UV light had very little effect on mold spores it was deadly to bactiria.
All in all with this experiment I would say adding UV light is not something that I would do if building a new flow hood. By using proper aseptic procedures a steril environment can be achieved with great results.

#26 phantasmal_undertow

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Posted 20 June 2016 - 01:19 AM

I thought about all the problems of sterilizing grain with uv -c and figured a pc would be easier. I initially thought of cooking the grain ,spreading it out so every kernel would be exposed, but it would be so bulky in a sab that it would be more trouble than its worth.

I bet it would work for agar plates and might be able to resterilize  plastic petri dishes.

 

 

If you really wanted to incorporate a uv-c light to have some effect maybe consider having one over the grains while they dry after being boiled but before being loaded into jars. Just a thought but they'd still get exposed to air before being loaded into jars and pressure cooked.



#27 TVCasualty

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Posted 20 June 2016 - 08:56 AM

No need to wait until Sunday. All four plates are showing some contamination. The 30 minute plate is showing less then the others but still infected. I can't say if it's just a old bulb or to far from the work area maybe just not enough time idk. It was a good experiment that wasn't to much of a loss. The flow hood works fine without it so still good to go. If I ever try something new with UV I'll bump this thread. .....

 

In any clump of opaque material (which would include a few mold spores stuck together) there will be a "shadow" under which there will be no UV exposure and so no germicidal effect.

 

Such a clump could be too small to see with the naked eye, which is why UV is really only a supplement to proper technique and cleanliness and can't act as a replacement for them (and why irradiating air -or water- after it's been mechanically filtered is far more effective than exposing it beforehand).



#28 CatsAndBats

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Posted 20 June 2016 - 10:13 AM

I am in contact with a microbiologist that works at the NIH. They said minimum of 60 min for sterilization using UV. IMHO, I think it would be an excellent way of (pre)treating a well constructed SAB/GB.  Just my .02

 

Oh and that bleach or h2o2 > alcohol in its effectiveness of one working aseptically.


Edited by catattack, 20 June 2016 - 10:14 AM.

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#29 TVCasualty

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Posted 20 June 2016 - 11:41 AM

I am in contact with a microbiologist that works at the NIH. They said minimum of 60 min for sterilization using UV. IMHO, I think it would be an excellent way of (pre)treating a well constructed SAB/GB.  Just my .02

 

Just be sure it has no plastic parts that will be exposed to the UV light! It will weaken and ultimately destroy any plastic in short-order at that level of exposure.


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#30 CatsAndBats

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Posted 20 June 2016 - 12:02 PM

I have two more cents.

 

I think the word 'sterile' is thrown around the OMCs a little too loosely. Aseptic is a much more accurate word to be used not only as a goal, but also more precisely how most of us actually work. Personally I try to manage the 'spore load' in an all encompassing way. Cleanliness might not be next to godliness, but it sure helps when attempting to grow entheogens (word origin, the god within). Patience, READING (sorry new kids, if you think you are reading enough, you aren't  :biggrin: ), and cleaning are the keys to this hobby IMHO. So examining and utilizing all  methods of aseptic work that we can, will improve our grows and the knowledge base in our community.

 

end catRant

 

carry on



#31 TVCasualty

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Posted 22 June 2016 - 09:58 AM

Yeah, most of what we do is "aseptic" work and not really "sterile" in a technical sense, but the degree of asepsis we must achieve is critical to success.

 

That's why UV by itself is not sufficient for tissue-culture work; unless one is using an insanely-powerful UV source (like from plasma-arc lights) then the strongest bulbs typically available only claim up to a 99% efficiency in terms of killing airborne microbes from a single pass (of air or water passing by the bulb).

 

The rating system for mechanical filters doesn't apply to germicidal UV "filters" (and vice-versa; the ratings systems are apples-and-oranges, which may lead to some confusion for those just starting to look into this stuff). For example, a true-HEPA filter is rated at 99.97% @ 0.3 microns, which means for every 10,000 particles that enter the filter that are 0.3 microns or larger, around 3 make it through.

 

UV bulbs are not rated for particle size like HEPA filters are, they're instead rated for their single-pass effectiveness against airborne (or waterborne) microbes. So a "99%" UV bulb kills 99% of microbes in a single pass, but only if they are directly exposed to the UV-C light. If larger particles are not filtered out before the air is irradiated with UV then a "99%" rating is meaningless. And even if all the large particles are mechanically filtered out of the air, a 99% rating still means that 100 out of every 10,000 microbes survive.

 

That's over 30 times as many surviving contaminants in the air as can slip through a HEPA filter, and that assumes the UV bulb is still working within spec, which after a few months may not not be the case. A HEPA filter actually tends to get more efficient over time due to clogging up with particles (which also gradually increases its static resistance until the flow is restricted too much and it's time to replace it).

 

Using UV after HEPA filtration means the UV would be killing 99% of the microbes that made it through the HEPA, so if all particles passing through a HEPA were microbes, a pass-through survival rate of 3 per 10,000 could drop to ~0.03 per 10,000 when UV is added. Since 3/10000 is perfectly adequate for tissue culture work with fungi, it appears to be unnecessary to combine UV with a HEPA filter.

 

But when UV is used to reduce the ambient spore load in the air throughout our whole house (such as by installing a light in our central HVAC duct), it can have a profound effect on our contamination rates once the cakes or trays are transferred to the FC and the misting/fanning starts. So I'm a big fan of UV, but only in a very specific context.


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#32 JACKOLANTERN

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Posted 22 February 2017 - 08:01 AM

Small UV C bulbs can be obtained at big box home improvement outlets such as the "blue store" in the outside lawn and garden department in the pond supplies for around 10 bucks. You just need to take it over to the electrical department and ask for the ballast for it and a way to wire it up. Also PLEASE PLEASE PLEASE, I can not stress this enough that staring at the light from one of these can definitely damage your eyes. Its kinds like staring at a welding arc though not as bright as one and it can cause temporary blindness. Be safe!871980400636.jpg


Edited by JACKOLANTERN, 22 February 2017 - 08:10 AM.

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#33 Justintime

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Posted 06 August 2017 - 11:26 PM

I picked up a UV box used by nail technicians to harden nail polish. Got it from my local recycling centre. Second hand. I don't think it works tho. I put syringes of spores inside it. Still contammed tho. Maybe the UV isn't strong enough or the bulbs are old.




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