First question I have is what kind of nutrient base conditions can we expect to start from? Should it be like Earth, or somewhere a bit more resource constrained (and how would it be constrained)?
I’d like to imagine solar reactors mimicking primordial goo to synthesise the essentials for these materials.
"A key unknown in creating such bio-mechanical structures in space is how the structure would be assembled. Feedstock must be provided (and relocated if necessary) to the growing edge, or to the area from which biological materials are being extruded. If aerobic organisms or mechanisms are required (grown in space and then desiccated by exposure to vacuum when growth is complete), the methods and support equipment required to preserve key aerobic variables (e.g., atmosphere, pressure, temperature) must be part of the biomechanical assembly system design."
Lots of nuanced details around your question in the doc! EDIT: I stupidly copy and pasted my local link to the PDF -- it appears this listing has been removed since posted. Here's another link to it https://govtribe.com/file/government-file/darpa-sn-25-51-dot...
Seems they're interested in precisely the question you pose, but coming at it from a few different directions
Anything you want and can launch into space. The program goal is being able to grow large structures. The intent seems to be using biology as a means to more efficiently transform launched mass into big structures.
I’d like to imagine solar reactors mimicking primordial goo to synthesise the essentials for these materials.