With the design of the WW system would it be easy to create a yeast culture by decanting the yeast from the sediment jar, storing it in the fridge, then adding some wort/yeast nutrient for a yeast starter for the next brew (assuming you want to use that type of yeast in the next brew) ?
I’ve also thought about the possibility of this however I think when the Sediment bottle is released the pressure change makes it impossible to get a pure yeast culture as it bubbles up. Also if you find a good yeast from a reputable supplier it should give you the same results always.
Good breweries will re-use yeast about 5-8 times. The best yeast is in the middle. The bottom yeast is dead, the top yeast was slow to flocculate to some extent and so you want the 1/3rd in the middle. For wet yeast you pitch with about 1% of the wort volume and it grows to 3%. So if you can take it off and get the middle 230 ml out that’s good but because it expands when the pressure is off you get a bit of mixing. In any case 230ml of that yeast all mixed up is pretty fine yeast anyway. So what you could do is keep 230ml of that in the fridge for no more than 7 days and re-use it. However in this case you need to aerate the next wort, to allow the yeast to make sterols and fatty acids in order to divide and grow again in the next fermentation. You need 8ppm oxygen in the wort which is hard for a homebrewer to measure. So either bubble air in with a fish-tank air pump or stir the hell out of it. But to reduce the risk of a ferment not going all the way, aerating in a yeast starter on a stir plate for a few hours in 1L of wort would do it. It doesn’t need to be over night like when you get wet yeast from Wyeast or White labs because that stuff is extremely weakened by being wet for so long (they’ve used up all there energy reserves) and because you have 230ml of it, it needs to be in a fully aerate wort for a while. So to avoid all this hassle we use dry yeast as they’re grown in a way that they don’t need a starter. Much easier. But to answer your question, yes, it can be done, but aerate the wort really well or the 230ml of yeast you need to add won’t grow well and fermentation will stop halfway. Cheers. Ian