I just looked after my drying cactus.
There is white mold.
How to remove the mold and do an extraction anyway?

kill the mold with some hydrogen peroxide...

and if you are doing an extraction...just make sure you filter your d-limonene and your vinegar after all pulls...and you should be fine

just remember we breathe mold spores constantly...but you just want to keep them to a minimum...but overall i think you should be ok to continue...just use the hydrogen peroxide

If you're going to extract the dried cactus i wouldnt worry about the mould too much, the basic conditions re adding lye will kill it off anyway. Besides, if you havent pre-washed/cleaned your dried cactus there's goin to be dust, dirt & all kinds of bacteria on the surface so its not that big of a deal.
Cactus teas are a different matter as you're going to be ingesting the solution that the cactus has been soaking in, so cleanliness is of a much higher priority (but if you're boiling/simmering down your tea the heat will destroy most bacteria!).

What I have found to work pretty effectively for gettin rid of most moulds on fresh cacti has been to douse the infected site in some kind of alcohol (IPA, ethanol, methanol). If that doesnt quite get rid of it you can rub off the mould and then douse it to prevent infection again.

Hope that helps

MIST it down with a weak hydrogen peroxide solution as Jorkest suggested OR lower the humidity to levels that do no accommodate the mold colonies ie go buy some damp rid(calcium chloride) at wallmart and put it in a sealed container with the cactus it will suck the water out in NO TIME.

PEACE
MV

I'd just cut the affected area out, or if it is wide spread, h2o2 sounds like a good idea.

FYI Drying a cactus should only take 1 day. Simply cut into 1/4" slices or thinner, put on cookie sheet(s) and point a fan at it. Flip after 6-10 hours, or whenever top feels dry. Done after 24-32 hours, sometimes less depending on thickness of slices. No heat required.

Even without a fan, cut into 1/4" slices, stand them up and wait 2-3 days......but a fan really helps.

Do be careful, A FEW molds give off waste that IS highly toxic (from experience growing mushrooms, but they are not white, but rather black or yellow molds), so killing the mold does not always = safe for consumption. It is not the mold in these cases that is deadly, but the molds waste. Killing the mold does not destroy these toxins.

Though, I'm not sure any toxic molecules would a) survive the B/A extraction b) be carried over to the NS solvent layer and end up in the final product....so you are probably 100% fine using the molded over cactus...