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Yeast Fermentation - Bio EE

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So I am on my analysis for the Bio EE and I'm stuck. I did yeast fermentation but the problem is the yeast fermented fructose faster than glucose. From research, it seems glucose should be faster than fructose. Of course, this could have been due to uncertainty or lab error but I'm not sure how to explain either phenomenon. How could they be fermented differently if they're both monosaccharides?

Thanks! :D

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Well I googled it, and I found a PDF that said

INTEREST in the phenomena of selective fermentation of mixtures of sugars

by yeast has been revived in the last decade, following the more precise

measurements of Willstiitter and Sobotka [1922]. The facts are briefly as


(1) That separate solutions containing more than 1 % of glucose or fructose

are fermented at equal rates by living yeast.

(2) That glucose and fructose in mixtures are fermented at unequal rates,

glucose being fermented faster than fructose by most yeasts, including

S. cerevisiae, while fructose is fermented faster than glucose by some yeasts,

among which are Sauterne yeast, S. pombe and S. exiguus.

I didn't read most of it, and it can be found here.

It also said

...he also estimated the rates at which these two yeasts ferment separate solutions containing glucose and fructose. These

separate rates of fermentation are of particular interest since Hopkins found

that, at concentrations of sugar below 1 %, brewer's yeast fermented glucose

faster than fructose. The Sauterne yeast, on the other hand, fermented

fructose faster than glucose at all concentrations of sugar tested, the effect

being more marked in dilute sugar solutions. According to the ideas to be expressed

in the present paper, the explanation of the phenomena of selective

fermentation is to be found in the relative rates of fermentation of solutions

containing low concentrations of the separate hexoses.

So perhaps more research on selective fermentation is in order?

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Although I don't know much about yeast, this sounds to me like an enzymic thing. I can't say for sure, but to point you in a direction where you might be able to figure it out, google "km and vmax" (Link) and you might consider whether one of the enzymes involved in fermentation of fructose perhaps has a low km and vmax, whereas one of the enzymes involved in fermenting glucose has a high km and vmax. Of course your results could be due to lab error, but if they're all saying the same thing (and I assume you've done plenty of repeats!) it seems unlikely.

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