if you are REALLY interested in fermenting, try this

here is the daddy of all fermented products, imo. it has not only just the few strains of probiotics that bio-k has, but a whole host of others. its very powerful, and you can ferment small amounts of it and thus the bottle can last a long time.

you can add a bit of this to some milk, add a little black strap molasses, and then leave it ferment. its best if you keep it warm, as with a yogurt maker. allegedly, this is the product that turned jordan rubin onto soil based organisms and cured him of chrones disease and inspired him to start the "garden of life" company.

if you want to culture your own bacteria, this is the way to go.

http://www.livesuperfoods.com/store/agora.cgi/00100/1a