Becker's World of the Cell 9th Edition by Lewis Kleinsmith, Jeff Hardin, Gregory Paul Bertoni

Exercise 7

Propionate Fermentation. Although lactate and ethanol are the best-known products of fermentation, other pathways are also known, some with important commercial applications.
Swiss cheese production, for example, depends on the bacterium Propionibacteriumfreudenreichii, which converts pyruvate to propionate
Fermentation of glucose to propionate always generates at least one other product as well.
(a)Why is it not possible to devise a scheme for the fermentation of glucose with propionate as the sole end-product
(b)Suggest an overall scheme for propionate production that generates only one additional product, and indicate what that product might be.
(c)If you know that Swiss cheese production actually requires both propionate and carbon dioxide and that both are produced by Propionibacterium fermentation, what else can you now say about the fermentation process that this bacterium carries out