Conversion of Sugar to Alcohol

This page shows the entire series of chemical reactions that take place in the conversion of sugar to alcohol in the production of grape wine. I do not pretend to understand any of this. This entire page is taken from Fig. 52 (page 165) of the book Technology of Wine Making by M. A. Amerine, PhD. and W. V. Cruess, PhD., published by the Avi Publishing Company, Inc. in Westport, CT, copyright 1960. For my purposes you start with a solution containing sugar and water along with yeast and things that make yeast happy. The end result is that every two sugar molecules are converted into one molecule each of ethanol and carbon dioxide. I have seen several requests, however, on newsgroups for the complete set of reactions and coments like "It's not that hard, is it?" when no one posts an answer. Well, the answer is "Yes," it is that hard, particularly to display this in text on a newsgroup. I finally broke down and decided to put it up on a web page where the formating was still difficult, but not impossible.

As I have said, I am not an organic chemist, nor a professional enologist. I do not pretend understand these reactions. Please don't e-mail me with questions about them. On the other hand -- I have done my best to transcribe this correctly from the book, but it is possible that I have made errors in the transcription, or that there were errors in the printing of which I am unaware. If, therefore, you are trained in either of these fields and spot an error, please e-mail me and let me know so that I can correct the error!

1. glucose1 (hexokinase)
(Mg++, ATP -> ADP)
2a. glucose-6-phosphate (glucose-6-phosphate dehydrgenase)
(TPN -> TPNH + H+)
6-phosphogluconate -> hexose monophospahte shunt system
2. glucose-6-phosphate (phosphohexoisomerase)
2b. fructose (hexokinase)
(Mg++, ATP -> ADP)
3. fructose-6-phosphate
(Neuberg ester)
(Mg++,ATP -> ADP)
4. fructose-1,6-diphosphate
(Harden-Young ester)
(Zn++, Co++, Fe++ or Ca++)
D-glyceraldehyde-3-phosphate + dihydroxyacetone phosphate
5. D-glyceraldehyde-3-phosphate
(Fischer-Bare ester
(triosphosphate isomerase)
5a. dihydroxyacetone-phosphate (a-glycerolphosphate dehydrogenase)
(H+ + DPNH -> DPN)
L-a-glycerol phosphoric acid
5b. L-a-glycerol phosphoric acid (phosphatase)
6. D-glyceraldehyde-3-phosphate + H3PO4 (triosephosphate dehydrogenase)
DPN -> DPNH + H+
7. 1,3-diphosphoryl-D-glycerate (phosphorylglyceryl kinase)
Mg++, ADP -> ATP)
8. 3-diphosphoryl-D-glycerate (phosphorylglyceryl mutase)
9. 2-phosphoryl-D-glycerate (phosphoenolpyruvic transphorylase)
10. phosphorylenolpyruvate (phosphoenolpyruvic transphosphorylase)
Mg++, K+, ADP -> ATP)
11. pyruvate (carboxylase)
acetaldehyde + CO2
11a. pyruvate (lactic dehydrogenase)
DPNH + H+ -> DPN
lactic acid
12. acetaldehyde (alcohol dehydrogenase)
DPNH + H+ -> DPN

ADP, ATP Di- and Triphosphates of adenosine. DPN+, DPNH. Oxidized and reduced diphosphopyridine nucleotides. (Also called coenzyme I and II.)
TPN+, TPNH. Oxidized and reduced triphosphopyridine nucleotides.
TPP. Thiamine pyrophosphate.
  1 Starch is converted to glucose-1-phosphate (the Cremer-Cori ester) with phosphoric acid and phosphorylase. Glucose-1-phosphate plus the enzyme phosphoglucomutase and magnesium ions is converted to glucose-1,6-diphosphate.
  2 Fructose-1,6-diphosphate is also converted to fructose-6-phosphate in the presence of fructose diphosphate, magnesium ions, and water.
  3 Phosphorenolpyruvate plus phosphorenolpyruvate enolase and ITP and TTP (Inosine di- and triphosphates) may also produce oxaloacetate.
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This page last updated on March 2, 2000