Why is dung and straw better pasteurized than sterilized?
There are several reasons for this. Dung and straw are used as so called bulk substrates. This means you are usually working with a greater quantity of those substrates and inoculate it with grain spawn. The second, probably more important reason is the contamination risk of sterilized substrates. When you pasteurize substrates at 160-170?F (71-77?C) some beneficial micro organisms, mainly bacteria, stay alive, inhabit the substrate and ?guard? it against other more aggressive micro organisms. Mushroom mycelium is still able to grow on this substrate though. This is the reason why you can inoculate bulk substrates with spawn in open spaces without taking special sterile precautions. If you sterilize the bulk substrate it becomes as much susceptible to contaminants as for instance rye grain or whole rice. This means that you would have to inoculate the big amount of bulk substrate in sterile conditions, in front of a HEPA hood. And this is not practicable if you have big amounts of the
