Sciencemadness Discussion Board

products produced through yeast fermentation

Yttrium2 - 14-9-2018 at 21:28

whats been produced since sugar to alcohol, and who studies , or knows how to deal with producing products through yeast fermentation. Can other microorganisms also

j_sum1 - 14-9-2018 at 22:49

Ethanol and carbon dioxide are the main products. But this varies. Not all microorganisms metabolise the same way. And not all behave the same under all conditions (availability of oxygen being one of the chief variables.)

Other products can include lactic acid, acetone, butyric acid, hydrogen gas and probably a bunch of other things. Then, given a but of oxidation you can have acetaldehyde and acetic acid which then lead to a bunch of byproducts: esters included.
Of course in the world of fermentation it is not just sucrose that is used and then you have whole fields of possible products which give a variety of flavours to your beverages.

Any yes, other organisms can be used for fermentation including some bacteria and various other non-yeast fungi.

Big field. I'm no expert. I'll shut up now.

Ubya - 15-9-2018 at 00:29

a few weeks ago i was intrested in butanol production using fermentation,
https://en.wikipedia.org/wiki/Acetone%E2%80%93butanol%E2%80%... this is just an idea of what can be done

markx - 17-9-2018 at 06:27

Even the most common bakers yeast fermentation of simple sugars produces a whole collection of different substances besides the ethanol and carbon dioxide being the main components:

Acetone, methanol, aldehydes, ethyl acetate (also acetate esters of higher alcohols), amyl alcohols (pentanol isomers), furfural, organic acids....just to name some.

The main problem is that one needs a very good fractionating column to separate just some of them out the main stew and it is quite a complicated mix.
For example a quite reasonably pure ethyl acetate fraction can be separated from the heads of a distillation run.
Methanol content is usually very low (but remarkable in products that are fermented using apples).
Amyl alcohols can be separated from congener fraction (tails) and furfural from the very end of the tail fraction if grains are used as the source of sugars. It is a lot of work and usually not worth doing on small scale, but for the fun of it I have separated the amyl alcohol fraction, concentrated it by leaching out the residual water with a saturated brine and used it to produce a sample of amyl acetate. Quite a flavorful ester....smells of pears, banana, and a whole lot of something else that I really can't place.

Yttrium2 - 27-9-2018 at 07:53

why does the yeast produce those compounds though?

macckone - 27-9-2018 at 10:54

Ethyl acetate is nearly impossible to separate from ethanol.
Ethyl acetate has a bp of 77C
Ethanol has a bp of 78C

Yes given enough reflux and enough runs you can get it out but it isn't easy. It is easier to decompose it with sodium carbonate or sodium hydroxide. If you are making ethyl acetate, the usual method is absolute ethanol and acetic acid over sulfuric acid or sodium bisulfate at reflux with an acid water scavenger (sulfuric acid acts as a scavenger).

unionised - 27-9-2018 at 11:20

Quote: Originally posted by macckone  
Ethyl acetate is nearly impossible to separate from ethanol.
Ethyl acetate has a bp of 77C
Ethanol has a bp of 78C

Yes given enough reflux and enough runs you can get it out but it isn't easy. It is easier to decompose it with sodium carbonate or sodium hydroxide. If you are making ethyl acetate, the usual method is absolute ethanol and acetic acid over sulfuric acid or sodium bisulfate at reflux with an acid water scavenger (sulfuric acid acts as a scavenger).


The azeotrope boils at 71.8C

Fulmen - 27-9-2018 at 11:47

Quote: Originally posted by Yttrium2  
why does the yeast produce those compounds though?


It's food. In the absence of oxygen they extract energy from converting sugars into other compounds.

macckone - 28-9-2018 at 06:41

Unionized, yes ethanol and ethyl acetate form an azetrope as well. But I can assure you that if you have significant ethyl acetate in your ethanol the only way to get it out is by using sodium hydroxide or carbonate.

And it is undrinkable if there is too much ethyl acetate.