What fundamentally separates a mature sourdough starter from pure baker's yeast?

Answer

The presence of bacteria creating acids

A mature sourdough starter contains a stable, symbiotic ecosystem including wild yeasts and lactic acid bacteria, whereas commercial yeast is primarily a single, concentrated strain of *Saccharomyces cerevisiae* without the necessary bacterial population for acid production.

What fundamentally separates a mature sourdough starter from pure baker's yeast?
culturefermentationbreadmicrobeyeast