Does all Yeast Create Alcohol when Sugars are Present?

[Bassman2003]

Hello,

This is a question for the biologists on the forum. I was wondering about yeast behavior. Does yeast always produce alcohol or are there strains that produce other substances or flavors?

Can yeast be engineered to not produce alcohol or to produce other flavors?

I know there are a ton of different yeasts in the world but just wondering. Thanks for your input.

 

[corax]

The Saccharomyces-related yeasts we all know and love are specialized sugar fermenters. Non-Saccharomyces yeasts ferment sugars to ethanol with varying levels of success. Traditionally there were groups of yeasts known as "non-fermentative", but most can apparently be coaxed into fermenting, albeit less thoroughly than Saccharomyces.

But note that when oxygen is present and the sugar concentration is low, Saccharomyces will switch from fermentation to respiration and consume any available ethanol.

As for what can be engineered, the sky's the limit.

 

[Bassman2003]

Thanks for your reply. I was just wondering if yeasts could be made to eat the sugars, create the flavors but not create alcohol. Sort of like a true non-alcoholic beverage creator.

 

[corax]

If you keep it oxygen-free, then yeast will ferment sugar to alcohol. If you add oxygen, it will eat up the alcohol when the sugar is used up, but in the process will probably create flavors you don't want. And many flavors you do want would be destroyed by oxidation in such an environment.

In order to preserve desired flavors and avoid off-flavors, the usual method of producing alcohol-free beer is to remove the alcohol after a normal fermentation, either by heat, vacuum or reverse osmosis.

 

[Bassman2003]

Yes, thanks. Having a strain of yeast that created great flavors without alcohol would be pretty interesting. Could this be achieved biologically or through engineering? I am not a biologist so I am asking towards anybody you is a biologist.

 

[Kent88]

I think the owner over at White Labs was heavily involved in a yeast gene sequencing project that finished up sometime in the past couple years. I think one of Brad Smith's beersmith vid/podcasts had him on talking about the project, and I thought it was interesting. I think there might have even been talk of GMO brewers yeast, which I think would be really nice, and not just because we could have yeast that glow green in the dark on St Patrick's day.

 

[AnthonyTD]

On a side note but related, I was trying to explain to my wife why bread doesn't contain alchol but I could not. Does the yeast create alchol which is baked off or is the yeast there doing something completely different.

 

[corax]

Yes, thanks. Having a strain of yeast that created great flavors without alcohol would be pretty interesting. Could this be achieved biologically or through engineering? I am not a biologist so I am asking towards anybody you is a biologist.

Oxygen is the problem. For any yeast to grow and not ferment they would need oxygen, and oxygen is the enemy of good beer flavor.

In some situations, other compounds besides alcohol can be produced by fermentation (eg, lactic acid), but these compounds tend not to taste very good. That might be the best target for a bioengineering project.

 

[BeerChemistWhiskey]

On a side note but related, I was trying to explain to my wife why bread doesn't contain alchol but I could not. Does the yeast create alchol which is baked off or is the yeast there doing something completely different.

I would point out for one that bread is baked well above the evaporation temperature of ethanol. It is the same process, it's just the CO2 that is desired in the rising of bread.

 

[Bassman2003]

Thanks for your replies. So I gather all yeast strains create alcohol when they are active/eating?

 

[bernardsmith]

Not a biologist but different strains of yeast can eat different kinds of sugars, so beer/wine yeasts eat simple sugars but there are yeasts in kefir grains , for example, that can eat more complex sugars, lactose is one. Brett, I think, can eat the sugars in wood - hence they can have a presence in oak barrels that can be difficult to remove.