Heat inactivation of viruses

[estación seca]

Tobacco Mosaic Virus is very similar to Cymbidium Mosaic Virus and Odontoglossum Ringspot Virus. I was looking for how to treat old LECA for safe reuse to prevent unrecognized viruses from spreading. I found the following. My conclusion is that pressure-cooking LECA at the high setting for 30 minutes (equivalent to 250 degrees F / 121C) should be more than enough.

http://www.jbc.org/content/140/2/509.full.pdf

THE DENATURATION OF TOBACCO MOSAIC VIRUS AT HIGH PRESSURES BY MAX A. LAUFFER AND R. B. DOW (From the Department of Animal and Plant Pathology of The Rockefeller Institute for Medical Research, Princeton, and the School of Chemistry and Physics, the Pennsylvania State College, State College) (Received for publication, May 19, 1941) Tobacco mosaic virus nucleoprotein (14), in common with many proteins, can be denatured by various means. A neutral [in pH] solution of the virus heated to about 70 [degrees C, 158 degrees F] will lose its infectivity rapidly and gradually become insoluble in dilute salt solutions.... If the virus solvent is made alkaline to a pH value of 10.5 or 11, this reaction will proceed at an appreciable rate even at room temperature.

[hypostatic]

If you "bake" your LECA, it should also denature any proteins or nucleic acids that would be of worry. You would just have to cook it for longer, so that the heat penetrates through the substrate fully.

For a pressure cooker, 5-10 min on high should be enough really

[estación seca]

I was thinking back to autoclave days. Irregular substances with various small nooks and crannies need very much more time at high heat to sterilize than smooth glass.

[hypostatic]

yeah, I guess it depends on how "thick" your sample is also.

LECA is fairly heat stable right? If you wanted to be super sure, you could do 500F in the oven for like an hour. Nothing should survive that

[Mr.Fakename]

Wet heat gives better results than dry heat.

More volume = more sterilising time indeed, but as LECA is very airy, 30 minutes probably is enough for a full batch.

I think pre-soaking the pellets might make the process even more effective.

[Orchidtinkerer]

viruses are all very simliar, freezing temps preserve them, heat kills them but viruses also can't survive drying out completely.

Dry any virus and it cannot survive more than 17 days at most.

[estación seca]

Tobacco mosaic virus survives in dry soil for decades. There are many references available. Different strains of cold viruses (coronavirus) have been reported to survive between 2 and 72 hours on dry surfaces in various studies.

[hypostatic]

Originally Posted by Mr.Fakename

Wet heat gives better results than dry heat.

More volume = more sterilising time indeed, but as LECA is very airy, 30 minutes probably is enough for a full batch.

I think pre-soaking the pellets might make the process even more effective.

Wetting the substrate would actually make the process to take longer, as the substrate would not reach a high enough temperature until the water boils away. Until that point, the LECA would stay at 100C.

Using a pressure cooker (or autoclave) allows you to bring that temperature up to 121C (250F). This is ONE of the reasons why food cooks much quicker in a pressure cooker.

[SouthPark]

Originally Posted by estación seca

My conclusion is that pressure-cooking LECA at the high setting for 30 minutes (equivalent to 250 degrees F / 121C) should be more than enough.

Definitely. Thirty minutes in a pressure cooker at high heat setting will do the trick.