Antifreeze in stool/FMT capsules, glycerol vs maltodextrin, -80 (medical freezer) vs -20 (home freezer)

SFBayFMT5

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I was reading through the published information on how OpenBiome processes their stool samples into FMT preparations. They state that the stool is dissolved in a glycerol/saline solution, consisting of 12.5% glycerol in 0.9% NaCl, before storing in a -80C freezer (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8082449/, see second paragraph under heading "Manufacturing").

I surmise that this solution plays the role of an antifreeze, similar to the antifreeze that HMorg offers to be added to their orders, although the HMorg antifreeze consists of maltodextrin and glycerol instead of glycerol and saline. Am I correct in inferring this?

If so, does adding antifreeze to capsules have any effect on their ability to stay preserved in a normal freezer? or are they still preserved just as well, only the bacteria do not sustain damage from ice formation the way they would if frozen without antifreeze?
 
although the HMorg antifreeze consists of maltodextrin and glycerol instead of glycerol and saline. Am I correct in inferring this?
No. Openbiome and most other places use glycerol. But glycerol can be a laxative, so HMorg uses maltodextrin by default instead, but gives the option for recipients to choose glycerol.

-80 (medical freezer) generally preserves better than -20 (standard freezer). Glycerol & maltodextrin are very similar.

You can search the FMT page https://humanmicrobiome.info/fmt/ for "maltodextrin" for more info. And the "freezing" section https://humanmicrobiome.info/fmt/#freezing for general info on that.
 
No. Openbiome and most other places use glycerol. But glycerol can be a laxative, so HMorg uses maltodextrin by default instead, but gives the option for recipients to choose glycerol.
What I meant was, does the antifreeze HMorg is using serve the same purpose as the glycerol other places are using? It sounds like the answer is yes.
-80 (medical freezer) generally preserves better than -20 (standard freezer). Glycerol & maltodextrin are very similar.

You can search the FMT page https://humanmicrobiome.info/fmt/ for "maltodextrin" for more info. And the "freezing" section https://humanmicrobiome.info/fmt/#freezing for general info on that.
My question was, does having antifreeze added negatively affect (i.e. reduce) how long stool lasts in a standard freezer (either from an effectiveness/efficacy or a safety standpoint), by interfering with the preserving effect of cold? Or does it actually have a positive effect because the beneficial microbes don't get stressed as much?
 
What I meant was, does the antifreeze HMorg is using serve the same purpose as the glycerol other places are using?
Yes.

My question was, does having antifreeze added negatively affect (i.e. reduce) how long stool lasts in a standard freezer (either from an effectiveness/efficacy or a safety standpoint), by interfering with the preserving effect of cold?
No, it's protective.
 
Do you know which other providers use/did use antifreeze vs. which don't? Taymount says on their website that they do, I don't know about other sources.
 
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