-Bread Machine CB: A true sourdough starter is nothing more than the flour and milk or water which sits at room temperature for several days and catches live yeast bacteria from the air. Most starter recipes today include yeast as an original ingredient as it is much easier and less time consuming. In addition, many sourdough bread recipes also indicate usage of yeast itself as it does provide a higher rising, lighter loaf. A sourdough starter should be kept in a glass or plastic bowl which has a tight fitting lid. I recommend a bowl instead of a jar as you can "feed" your starter right in the bowl easily.
Bread Machine Pizza Crust recipe