[Hnrobert42]

Maybe it’s because you have to ship stainless steel from Earth. Maybe the mass of the fungus can be grown from CO2 from respiration. The carbon originally coming from food, which has to be shipped up. Lots of maybes, but you know, maybe...

[dnautics]

> Maybe the mass of the fungus can be grown from CO2 from respiration.

That's not a thing. Fixing carbon to a usable form [0] using "general biological energy source" to the carbon pool is extremely difficult (there are only four and a half, counting c3 vs c4 as a half, pathways known) and requires complex machinery to achieve.

[0] assimilating carbon dioxide in general is not difficult, even humans do it but it does not enter the general carbon pool and is effectively only transiently converted out of CO2, and net does not contribute to biomass.

[lowdose]

Zeolites can do this. https://en.m.wikipedia.org/wiki/Zeolite

[DuskStar]

Either you ship steel, or you ship biological material - you're shipping things either way. (And if you can do ISRU, then steel or just plain cast iron is available)

[_emacsomancer_]

Steel doesn't reproduce though.

[DuskStar]

Reproduction doesn't create matter ex niliho, either. And in space, organizing the matter is far easier than getting the matter in the first place.

[lopmotr]

To grow fungus from CO2, don't you first have to grow a plant then let the fungus eat dead plant? Plants require (heavy) equipment to support them.

[labawi]

If it can photosynthesise (on gamma rays no less), then perhaps not. Mold can grow on concrete walls and stuff, so not sure what it needs.

[lopmotr]

It sounds like this fungus only produces energy, and doesn't fix carbon like photosynthesis does.

Mold growing on concrete walls is actually living off the dust and other organic debris that accumulates on the surface if you don't clean it.