help please

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MIKKI020490
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help please

Post by MIKKI020490 » Thu Apr 26, 2007 11:36 am

hi does anyone know what the ph needs to be in the tempreture yeast enzyme planning exercise
please help :D

blcr11
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Post by blcr11 » Thu Apr 26, 2007 3:33 pm

Yeast media recipes I've seen adjust to pH 7.2--if that helps.

But I really suspect anything between 5.5 and 7.8 will do for this experiment. You adjust the pH of the culture media when you're trying to grow things for more than an hour or two. You're not trying to get the yeast to grow at all, neccessarily, never mind for more than a few hours. You just want any metabolic enzymes that may remain active after heat treatment to keep on working for pehaps another 30 minutes.

I guess if I had to cheat towards acidic or basic conditions, I would go down in pH rather than up. Adjusting media to pH 7.2 probably anticipates that metabolism will acidify the solution to some extent. CO2 production should acidify media and since yeast normally make ethanol and CO2 out of sugars, I would guess yeast would be happy in at least slightly acidic media (certainly pH 6-6.5, maybe even lower).

Mind you, I don't think it's a bad idea to adjust the pH to 7 or 7.2 (with what, phosphate buffer? or PBS? or something like that?). I just don't think it's super-important for the experiment. Of course, I can always be wrong.

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