Expert: Walter Hintz - 2/17/2008

Question
Dear Mr. Hintz

Thank you very much for reading this message. I am planning an experiment into the rates of fermentation by yeast using different concentrations of the same substrate in my college and I was wondering if you could offer any advice to aid my investigation.

I understand the basics of how yeast ferments sugars but I'm getting a bit confused into the more in-depth explanation as to how this happens (i.e. pyruvate converted to ethanal and then reduced etc). If you could put the explanations into steps of how fermentation actually happens it would be hugely appreciated!

secondly, my experiment at the moment is to measure the levels of carbon dioxide evolved from the reaction at regular intervals, with different concentration substrates being fermented. it's a basic experiment and i am hoping you could think of a more scientifically accurate way of measuring rates of fermentation by yeast.

Thank you so much for any advice you can offer, it will be massively helpful!

Thanks again,
Adam Shellard

Answer
Hi Adam
During alcoholic fermentation 2 molecules of three carbon pyruvate are split (with water) into 2 molecules of acetaldehyde and 2 molecules of CO2 The acetaldehyde then accepts H and electrons from NADH and becomes ethanol.
 There are methods of measuring the fermentation using special instruments to measure enzyme activity but I am not an expert in this process. I googled measuring yeast fermentation and there is some information there.