Here's an interesting study that challenges the practice we homebrewers use of not re-using yeast after just a few times.
They report no changes after 13 serial re-pitches and in another study, they found no appreciable difference after re-pitching a lager strain 135 times.
Also mentioned is that shape of fermented doesn't really effect the beer.
http://www.scientificsocieties.org/jib/papers/2009/G-2009-0730-597.pdf
from the journal of the institute of brewing. Vol 115 No 2. 2009
this seems to be further backed by this study from 2007:
http://www.scientificsocieties.org/jib/papers/2007/G-2007-0420-478.pdf
They report no changes after 13 serial re-pitches and in another study, they found no appreciable difference after re-pitching a lager strain 135 times.
Also mentioned is that shape of fermented doesn't really effect the beer.
http://www.scientificsocieties.org/jib/papers/2009/G-2009-0730-597.pdf
from the journal of the institute of brewing. Vol 115 No 2. 2009
this seems to be further backed by this study from 2007:
http://www.scientificsocieties.org/jib/papers/2007/G-2007-0420-478.pdf