Spawn is mycelium grown on sterilised grain, usually wheat, in bottles or bags. The grain is only a carrier. The living part is the white mycelium wrapped around each grain.
A laboratory keeps a pure culture of the fungus on a jelly called agar. From that it grows mother spawn on grain, then multiplies it into the commercial spawn you buy. This needs a pressure steriliser called an autoclave and a clean-air cabinet. The MIDH spawn unit norm lists sterilisation, inoculation and incubation rooms, an autoclave and a laminar flow chamber. NHB gives 25 to 27 degrees for incubation and cold storage for finished spawn.