Check this out: http://www.thefreshloaf.com/node/37259/mythbusters-grain-yeast-or-air-yeast http://www.thefreshloaf.com/node/37259/mythbusters-grain-yea... It

Check this out: http://www.thefreshloaf.com/node/37259/mythbusters-grain-yeast-or-air-yeast http://www.thefreshloaf.com/node/37259/mythbusters-grain-yea... It seems like the source of microorganisms is from the input grain itself, not what's in the air.