- Jun 8, 2010
- Reaction score
- Houston, TX
First yeast do not want to procreate, they are reacting to external stimuli. Second, your example is describing Lamarckism which does not apply here. What is actually occurring when you grow yeast in sucrose, glucose or any other sugar is that you are expressing the genes for to import and use these sugars. It will take many generations for these cells to become adapted to using only one type of sugar efficiently. I would expect it would take thousands of generations under highly controlled conditions and population sizes to evolve strains to that lose their efficiency to use maltose.Think about it.
A cell eats a little nutrient and a little food. It wants to procreate. It splits. Using the supplied foods it has, the next cell will be able to use those same foods a little better. The new cell does this same thing. Now this continues for several generations with each new cell being able to use the foods that are available to it better than the previous.
What is actually occurring when you grow yeast in sucrose, glucose, or other sugar sources for a starter is that you are encouraging the yeast to express the genes to take in the sugar and use that sugar for energy. The lag time that occurs after pitching is due to the lack of transporters for other sugars in the cell membrane and the necessary enzymes for use in fermentation. The longer you grow the yeast in the non maltose sugar media the longer it will take for the maltose specific enzymes to be produced.
Actually, brewer's yeast is not haploid. It is actually polyploidy and/or a aneuploid. Strains used for brewing sporulate poorly and many of them that are formed are nonviable. These strains may have evolved this polyploidy genome structure for gene dosage. Incomplete cell division may have occurred during a fermentation and thus the yeast cell had twice as many copies of the genes for transport metabolism of maltose. These cells proliferated and the duplicated genes were retained. This actually creates a situation where recessive mutations will be highly masked in the genome and you will less likely to see mutations in a few generations.The issue isn't actually mutation. The commercial yeast cultures we're using are very pure in terms of containing only haploid cells, and even if they weren't, there wouldn't be enough generations for mutation to be a concern.
I'd highly recommend against that. You would be breeding your yeast to digest table sugar and they won't be able to make the enzymes required to break down maltose as well. So, you'd be pitching a weaker yeast and could have fermentation issues. Given the choice, I'd rather just pitch what you have without a starter and aerate really well before using a table sugar starter.
I think an experiment is in order. The wort in your beer contains small amounts of glucose and sucrose. When yeast are pitched they will first go into lag phase. They do this because most pitched yeast come from a nutrient deficient fermentation media. They are faced with three main stressors, glucose, oxygen, and osmotic pressure. After growing in maltose rich environment they will have lost most of their ability to transport glucose into their cells. In the presence of glucose the cells will use this molecule and the cells will start to create the proteins needed to transport and metabolize glucose. Then when the glucose becomes depleted the enzymes for sucrose need to be created. Then sucrose becomes depleted and now the genes to metabolize maltose are expressed. I would feel that growing yeast in a starter under aerobic conditions in a glucose media would actually reduce the lag phase. A shorter lag phase will mean the yeast will have higher vitality and viability than yeast with a longer lag phase. In the next month or so I will try pitching from yeast grown in a few different media and see what happensAll published and all conspiring to spread propoganda that sucrose alone does not make a good starter for beer fermentation.
But please, do prove them wrong.