35. What happens if I start my starter with commercial yeast?

Many people believe that a starter started with commercial yeast will
eventually be "taken over" by wild yeast.  This is a good thing, and
the quality/predictability of the resultant bread should improve as
this happens, since commercial yeast isn't really designed to be used
that way.  Until that process is completed, the starter is in a state
of transition toward a desired end-state where wild yeast and
bacteria maintain a balanced, stable, symbiotic relationship.  It
follows that an evolving starter will produce breads with differing
characteristics as the nature of the starter changes.  Only a stable
starter will produce consistent results.

It can actually take quite a while for a starter (even one that began
without commercial yeast) to reach a good balance of microbiological
life.  This is one of the reasons why many bakers use cultures from
long-established starters (why go through all the time and trouble to
nurse your starter to a balanced state when there are lots of
already-balanced starter cultures out there with proven
characteristics?).

-Sam

There was an experiment done by a Dutch group: baker's yeast didn't
survive more than two refreshments of a sourdough culture. I think
that it's the acetate that kills the yeast as it is less acetate
tolerant than sourdough yeasts.

-Michael