What other sources are there for yeast without purchasing specific supplies of any kind?
I’ve done several lactose fermentation experiments and am currently playing with figurative fire by washing and running fruits through a food processor, letting them go active in a (burped) container and then adding them to other fruit juices. Currently I have a small apple for yeast that I added to pealed lemons and some lemon juice. I have no expectations for the results, and intend on buying nothing.
The fresh fruit should work. Are you asking if a bottle of wine would give you yeast? The answer is generally no. Most wine has stuff added to stop fermentation. It may also be filtered to remove yeasts, etc.
What about when the wine has some extra bubbly? I thought that was due to post bottling activity. Would that also mean some live activity potential?
Maybe! I don’t know enough about making champaigne to be able to say.