First, adding yeast to plain sugar water will reduce its ability to consume maltose. THis is bad. If you want to harvest from a bottle, first let the bottle settle in your fridge for several weeks, then open and pour all but the last oz or so into a glass. Then flame the bottle opening and pour into a 1.030 starter made with dme or lme. You will have to step up the starter several times in order to grow enough yeast for a 5 gallon batch. Also keep in mind that professional breweries don't necessarily bottle with the same yeast they use for fermentation.