« on: August 27, 2010, 10:53:49 AM »
Tom,That will be totally fine, although I'm not sure you even need the mix.
What do you think about doing the first and second step ups for a big starter with a glucose/dme mix and then the final starter with all DME? I have been considering ways to reduce the cost of making large starters, short of doing a mash just for starter wort.
Basically, high levels of glucose repress the expression of maltase regardless of the presence of maltose, and it happens quickly - in less than 20 minutes IIRC, the levels of maltase are falling. The yeast will preferentially ferment the glucose, then when that drops below some threshold they will turn on the maltase genes and go after the maltose. So by doing a mix for the first couple of steps they'll essentially be yo-yoing between the two sugars. This is not especially stressful for the yeast though, they're fine - the only difference is the expression of all of the maltase genes. I don't remember how many there are in the cascade . . . ok, according to SGD there are 10 that are directly involved in maltase, but only 2 are the actual enzymes themselves. But that doesn't include all of the genes needed, because there are maltose permease genes. Anyway, I wouldn't worry about these details much, I just thought you'd be interested.
Bottom line, supplementing your starters with glucose is fine, especially if the last step before pitching is all DME. You could use sucrose (table sugar) for that matter, maltase can invert that too, it's cheaper than glucose, and won't suppress maltase the way straight glucose does.