Dunder Pit Starter Culture...

[der wo]

AFAIK the shizosacch. is relative neutral, has a high temperature resistance, ferments slower and works in a similar pH range like the bacterias.

I think with the high pH also the normal yeast doesn't have a problem. But schizosacch. would have a problem in a normal (very acidic) brandy mash.

But yes, I think, because of the slower fermentation speed, the overall process with the bacterias has to be controlled different. Perhaps you have to introduce the bacterias more carefully/later.

Only very few distilleries use this special yeast. It's not like this is the one and only Rum yeast. All cheap and midprice Rums are made with fast fermenting normal yeast. Or a few of them perhaps are flavored a bit with a small amount of schizosacch.-Rum.

[Single Malt Yinzer]

get a large crock and put your rum backset into it and cover with a cheesecloth. Set it in your basement and wait.

^That. Dunder is an expression of terroir. It will be the bacteria/yeast/etc that is around you. Give it a week and you'll have a party in there even if you don't know it. You might see stuff happening at that point. After a month you'll have a good pellicule or other stuff on the top of the dunder. The types of funky stuff that lives in there will be your mix. No one else will have that same proportions. Typically one type of bacteria/yeast will dominate but there will always be a grand mix of everything.

I use a 5 gallon plastic carboy with a couple paper towels over the top. I leave it half full for ease of movement. For a 5 gallon wash a cup or two 24-48 hours after you start to ferment is more than enough.

And I would avoid Malic acid or Malic acid fermentation. I've read it can reduce esters. I'm not quite sure the exact way it does it but it seems to reduce fatty acids somehow. Fatty acids lower the pH and are precursors to esters. Without them you don't get the funky stuff.

i have started my first dunder pit (controlled?)

I get that you're attempting to isolate your specific bacterial mix, but in the end once exposed to the environment you're going to get a mix anyhow. If you want to only have specific bacteria in your wash use the starter cultures from the lab directly, the same as pitching yeast. There is no real control with dunder. The dominant yeast/bacteria/etc will be a factor of the environment and the feedstock remnants (sugars, nutrients, pH, etc) of the stillage put in it. Even if you put equal amounts of 5 different cultures nature will favor some over the others. That mix will not remain the same. It will change anytime you add something back into it, or the temp changes, or the pH changes. This is terroir. It is what will make your rum your rum, and your neighbors will be just slightly different, and someone from across the continent (or island, in your case) will be entirely different.