The simple answer is you can use it in anything that uses yeast, as well as in things that use other forms of leavening. HOW you use it is where the art is. 🙂
Most instructions for maintaining a sourdough starter at home basically go like this:
Divide in two
Throw half out (or find something to do with it)
Feed other half, possibly using some to make bread tomorrow
Most commercial sourdough instructions go like this:
Feed
Divide in two
Use half to make bread
With the former, you have to find things to do with the half you throw out, for example, use it in pancake batter. With the latter, it assume every time you feed it you're also planning on baking with it shortly thereafter.
A sourdough culture is generally most active during the period from a few hours to a day after it's been fed. If you're a commercial baker, you're probably baking sourdough every day anyway, and you have the space available to feed your starter without throwing half of it out.
One exception is if you follow the Chad Robertson's (Tartine Bakery) method. He has you use just 5% of the starter to start the next batch, so it is what he calls a 'young' starter, meaning it isn't as acidic. He also talks about how refrigeration of a starter changes the bacteria composition to favor ones that produce more acid. I doubt that he throws out 95% of his starter in his bakery on a regular basis, so I suspect that the routine he gives for home use is different than the one he uses for mass production.
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