Note that Denny is now using SNS starters. That process gives the yeast oxygen before pitching it into the beer. Is it enough oxygen? The inventor of the SNS method says yes, but I am not convinced. I think that some kind of aeration during the transfer from kettle to fermenter is still worthwhile. I have a wine-type aerator that I put on the end of my transfer hose. I no longer use oxygen except for very high gravity beers.
Anybody that knows biochemistry and yeast (and any cell) aerobic metabolism can tell you that there won't be any significant yeast growth if you don't oxygenate at pitching.
If you have enough viable and vital cells at pitching (whatever the method used to produce the cells) to carry the fermentation, then the wort will ferment, if not, it won't ferment completely.
Yeast growth produces secondary flavor compounds, so beer from a fermentation with yeast growth will taste differently from beer produced with no yeast growth.
Better or worse is for the brewer to decide.
Is it enough oxygen?
It depends.
Is NOT enough to produce significant growth during the main fermentation.
It may be enough to produce sufficient cells in your starter depending on many factors including initial count and vitality, nutrients provided and oxygen provided.
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If by metabolism you mean respiration, then brewers yeast can't be put in the same category as "any cell". Yeast in beer wort do not use the oxygen for aerobic respiration because of the Crabtree effect. At the sugar concentration found in even weak beer wort, yeast will always use the anaerobic fermentation pathway to multiply, regardless of how much oxygen is present. Oxygenating the wort, whether via splashing or stone, does not necessarily result in more cells, it results in stronger cells that can more easily cross the finish line.
That was not my point.
Cells, including yeast, don't have the ability to store oxygen.
So, you can't give the oxygen "in advance".
The statement "yeast will always use the anaerobic fermentation pathway to multiply" is incorrect.
You can easily disprove this by weighing the yeast biomass pitched and the final yeast biomass after fermentation under different oxygenation rates.
That's why we shake or use stir plates or bioreactors.
Can yeast multiply anaerobically? Yes, of course. But you produce much more yeast with oxygenation.
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