Understanding Brettanomyces

Reads 3076 • Replies 12 • Started Tuesday, November 17, 2015 2:07:09 PM CT

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HornyDevil
14:07 Tue 11/17/2015

I’m going to keep this pretty simple, but if you guys have any questions about specific parts of this post, feel free to ask away. By the way, this is not my work. This is just stuff that I’ve read, but I feel as if I have a pretty good hold on it and would like to share it with the board.

The reason that I’m writing this is two-fold. The first is to lay down a foundation for one of the most misunderstood yeasts out there. The other is to stimulate much needed dialogue on this board. There will be some generalization, but I’ll try to keep the discussion as specific as possible. This first post is going to be a bit of a teaser, but there will be more if you guys want.

Brett does what it does because of one thing. Precursors. Sure it is able to metabolize chemicals differently than most Saccharomyces strains (Sacch/Brett Trois excluded) and is able to ferment longer sugars than Sacch. does as well, but without the precursors, there is no work for Brett to do. It’s ability to do this, however, varies greatly from strain to strain. This is a hallmark of Brett. Great variability from strain to strain.

Brett has the ability to esterify acids (mostly volatile fatty acids or VFAs) into esters because it has very high esterase activity (as CLevar said in the other thread). This means that it combines them with ethyl alcohol (when present) to form a different compound. Said compound is usually beneficial to the resultant beer, but not always. Ethyl acetate is a good example of non-beneficial esterification. In low quantities it presents apple and pear. High quantities, nail polish remover.

Brett also has the capacity to reduce vinyl derivatives of hydroxycinnamic acids into their ethyl state. These acids are derived from the hops and malts used to make beer, so beers with high levels of ferulic acid, for instance, have the opportunity to have more Brett character in the end. However, Brett does not have the level of ferulate hydroxylase that Sacch. has, so it can’t produce as much vinyl derivative as Sacch. can to be further reduced into the more potent ethyl one. This is the reason that 100% Brett beers tend to be less Brett-y than a beer that is primarily fermented with Sacch. and then finished with Brett. This is also why traditional lambic producers use a high percentage of unmalted wheat and a LOT of whole leaf hops, aged though they may be, they are a very good source of p-coumaric and caffeic acids, the other hydroxycinnamic acids responsible for Brett character.

 
HornyDevil
14:10 Tue 11/17/2015

Brett possesses the enzyme glycosidase (both alpha and beta), which not only allows it to break down fermentables up to 9 sugars long (sacch. can only break down fermentables up to 3 sugars long), but also allows it to liberate sugars that are bound to other chemicals, like glycosides in hops. This also creates new aromatic compounds, which is why a hoppy beer fermented with Brett, will, very probably, smell different from the same one fermented with Sacch.

I think this is enough for now. I’ll let CLevar post some stuff about THP.

Any questions or comments?

 
barncatmatt
beers 2287 º places 71 º 15:16 Tue 11/17/2015

What are your thoughts on pitching bret with sacch in primary vs pitching sacch, letting it do its thing, and then pitching bret?

 
HornyDevil
15:43 Tue 11/17/2015

Originally posted by matt7215
What are your thoughts on pitching bret with sacch in primary vs pitching sacch, letting it do its thing, and then pitching bret?


Some people will say that copitching Brett and Sacch will give you similar results to pitching Sacch first then pitching Brett in the secondary. I have found that if produces something in the middle of 100% Brett fermentations and Sacch. primary/Brett secondary fermentations.

However, since Brett grows more slowly than Sacch. does (longer lag phase), it will definitely be more towards the Sacch. primary/Brett secondary side than it will be towards the 100% Brett side of things.

That’s the general answer, but, again, these situations are highly dependent on which Sacch. and/or Brett strains that you use.

In other words, if you did three identical beers with the same Brett and/or Sacch. strains to ferment them: one 100% Brett, one a Brett/Sacch. copitch, and one Sacch. first and Brett once the Sacch. finished, I think that you’d find the later two beers to me more similar than the first and you might not even be able to tell them apart.

 
lithy
beers 2996 º places 156 º 07:07 Wed 11/18/2015

This is probably a good spot for this question that I’ve had floating around for a while and not been able to find any answers.

Brett is suggested all the time for cleaning up diacetyl specifically in sour beers where the major diacetyl producer is pedio.

Does it reduce by absorbing diacetyl/VDKs just like a normal sacch strain and metabolizing it enzymatically? Does it produce any different compounds than Sacch when doing this?

"Yeast reabsorb diacetyl and convert it to acetoin and subsequently to 2,3-butanediol (Fig.4)."
http://www.whitelabs.com/sites/default/files/Diacetyl_Time_Line.pdf

Just curious, I’m assuming Brett gets mentioned a lot because if it is already a sour beer you might as well use wild yeast, but for the purposes of diacetyl reduction it seems that any yeast would give you the same benefit.

 
CLevar
places 23 º 10:41 Wed 11/18/2015

I’m a little more scatter brained than usual due to some (exciting) personal stuff that’s going on right now, but I can try the tackle the diacetyl question. You will have to forgive the lack of italics and proper nomenclature- I’m cireently on my phone and my sleep deprived brain can’t be bothered to go through the dumb formatting

Brett goes through the same diacetyl-->acetoin-->butandiol but there is an important difference. Brett is subject to what’s known as "Custers Effect", which essentially means that the rate of glycolysis (sugars down to the level of three carbon compounds) and fermentation is *increased* in the presence of oxygen or alternative electron acceptors (Though with enough oxygen you run into issues of acetic acid production, low EtOH titer, and poor attenuation...but I digress. #brettsnotsourbro). As I inderstand it, the conversion of diacetyl-->acetoin-->butandiol stimulates the activity of Brett due to this effect. Indeed, acetoin has been used in a number of publications to stimulate Brett to look at fermentstion patterns, etc. Sacch is not subject to this same type of regulation. So an argument could be made that Brett is better suited simply due to the stimulation that these compounds provide.

Additionally, it’s also worth thinking about is where the diacetyl is comin from- some of the LAB that produce diacetyl also produce polysaccharides thay can also be used by Brett. I’m not sure how well the composition of these polysaccharides has been studied (as it relates to beer production and Brett physiology and metabolism) but adding Brett to viscous beer (ie, viscous due to these polysaccharides produced by some LAB, sometimes referred to as "ropey" beer) decrease the viscosity much more rapidly than do Sacch strains. Lots of other possible explanations for that observation (pH tolerance, etc) of course.

 
HornyDevil
14:21 Wed 11/18/2015

So . . . what does this all mean in the construction of Brett beers? Here’s what I would recommend for both 100% Brett fermentations and Sacch + Brett fermentations. Other mixed microbe fermentations, like those that include lactic acid bacteria, I’ll leave for later.

1) Use a simple grist with barley and wheat or oats to increase your mouthfeel via beta-glucans, as most strains of Brett are hyper-attenuative and tend to leave beers tasting thin.

2) Do a ferulic acid rest. More ferulic acid = more Brett character, especially in beers that you use Sacch. first. In those beers Brett will take the increased amount of 4 vinyl guaiacol (as compared to a 100% Brett beer) and reduce it into 4 ethyl guaiacol which has a smoky, spicy, and clove character.

3) Use a small bittering charge of high alpha hops, as if you use too much vegetal matter in the boil, you run the risk of Brett using the caffeic acid that is liberated from the hops to create a beer with a rubbery, plastic-y, and/or medicinal character.

4) Use as many hops as you want after flame out. The more hops used after the boil, the less caffeic acid introduced into the beer and the greater the chance for Brett to make more interesting aroma compounds by cleaving glycosides from the hops.

5) Make a starter with your yeast. "Stressing" it will do very little, if anything. However, different strains do respond differently to underpitching.

6) If you’re using a Sacch strain, use a highly clove forward strain and/or one that produces a decent amount of glycerol. The former is because those strains produce a lot of 4VG. The second because of the hyper-attenuative nature of many Brett species.

7) Expect a longer fermentation, especially for 100% Brett beers. Most normal gravity beers will reach a stable terminal gravity in the 4 - 6 week range, but higher gravity ones will probably take a little longer. I tend to give all of mine at least 8 weeks, just to make sure.

 
HornyDevil
14:36 Wed 11/18/2015

Originally posted by CLevar
some of the LAB that produce diacetyl also produce polysaccharides thay can also be used by Brett. I’m not sure how well the composition of these polysaccharides has been studied (as it relates to beer production and Brett physiology and metabolism) but adding Brett to viscous beer (ie, viscous due to these polysaccharides produced by some LAB, sometimes referred to as "ropey" beer) decrease the viscosity much more rapidly than do Sacch strains. Lots of other possible explanations for that observation (pH tolerance, etc) of course.


I have not heard much on this front, but it is quite an interesting subject. The differing abilities of Saccharomyces and Brettanomyces to process exopolysaccharides, that is.

 
GarethYoung
beers 1111 º places 27 º 04:43 Thu 11/19/2015

Originally posted by HornyDevil
Brett possesses the enzyme glycosidase (both alpha and beta), which not only allows it to break down fermentables up to 9 sugars long (sacch. can only break down fermentables up to 3 sugars long), but also allows it to liberate sugars that are bound to other chemicals, like glycosides in hops. This also creates new aromatic compounds, which is why a hoppy beer fermented with Brett, will, very probably, smell different from the same one fermented with Sacch.

I think this is enough for now. I’ll let CLevar post some stuff about THP.

Any questions or comments?


Thanks for starting the thread. Good to have some more home brew chat on here. I’ll have a read and a think to see if I’ve got anything interesting to add.

Here’s one thing though:

Not all strains of brettanomyces produce those glucosidase enzymes, though lots do and more produce alpha than beta, I believe. So if you have a strain, for example, that doesn’t produce beta glucosidase, then it can’t ferment, for example, lactose (since the two sugars are held together with a beta bond). So you could make a lactose sweetened brett beer and get high residual sugars. Good to know if you fancy a bretty milk stout, for example. Those strains won’t, as you say, be able to break the bonds in glycosides though, so you should get, for example, different hop character in those beers than in beers with strains that do produce those enzymes.

One interesting thing I’d like to read more about is this: apparently there are intracellular and extra-cellular versions of glucosidase enzymes, where the former are active inside the cell and the latter outside. This might well have an effect on flavour. If the enzymes are breaking down the sugars inside the cell, it seems likely that more of the resulting simpler sugars will be fermented inside the cell by the brettanomyces strain itself. If the enzymes are extra-cellular, then, again presumably, the sugars will be available to whatever other organisms are in the culture (perhaps a saccharomyces strain, perhaps another brettanomyces strain or bacteria).

So it may be that whether the enzyme activity is intra or extra cellular will make a difference, in addition to whether they merely produce alpha or beta glucosidases. Be interested if anyone knows more about this.

 
GarethYoung
beers 1111 º places 27 º 04:48 Thu 11/19/2015

Originally posted by HornyDevil
Originally posted by matt7215
What are your thoughts on pitching bret with sacch in primary vs pitching sacch, letting it do its thing, and then pitching bret?


Some people will say that copitching Brett and Sacch will give you similar results to pitching Sacch first then pitching Brett in the secondary. I have found that if produces something in the middle of 100% Brett fermentations and Sacch. primary/Brett secondary fermentations.

However, since Brett grows more slowly than Sacch. does (longer lag phase), it will definitely be more towards the Sacch. primary/Brett secondary side than it will be towards the 100% Brett side of things.

That’s the general answer, but, again, these situations are highly dependent on which Sacch. and/or Brett strains that you use.

In other words, if you did three identical beers with the same Brett and/or Sacch. strains to ferment them: one 100% Brett, one a Brett/Sacch. copitch, and one Sacch. first and Brett once the Sacch. finished, I think that you’d find the later two beers to me more similar than the first and you might not even be able to tell them apart.


For what it’s worth, I always co-pitch at the start of primary. Like you said, the difference in lag phase will make this method closer to the brettanomyces-secondary process than one might think, but you do get differences. The brettanomyces, typically, will be active fairly quickly, so you’ll get brettanomyces character more quickly. You’ll also get slightly different production of aromatic compounds, since the brettanomyces will be active both at the end of saccharomyces fermentation (where the environment is low-nutrient, high alcohol, low pH and higher in fermentation biproducts from other strain), but also at the beginning (higher pH, which makes a difference) where it will get a greater chance to ferment simple sugars. I tend to find (though this is anecdotal and purely from smelling things) that the brettanomyces seems to produce some fruity esters here that you might not otherwise get, without sacrificing funk.

As a rule of thumb, I think the broader the palette you give brettanomyces to work with the better, so having it ferment under a wider range of conditions seems like a good idea.

 
GarethYoung
beers 1111 º places 27 º 04:56 Thu 11/19/2015

Originally posted by CLevar
I’m a little more scatter brained than usual due to some (exciting) personal stuff that’s going on right now, but I can try the tackle the diacetyl question. You will have to forgive the lack of italics and proper nomenclature- I’m cireently on my phone and my sleep deprived brain can’t be bothered to go through the dumb formatting

Brett goes through the same diacetyl-->acetoin-->butandiol but there is an important difference. Brett is subject to what’s known as "Custers Effect", which essentially means that the rate of glycolysis (sugars down to the level of three carbon compounds) and fermentation is *increased* in the presence of oxygen or alternative electron acceptors (Though with enough oxygen you run into issues of acetic acid production, low EtOH titer, and poor attenuation...but I digress. #brettsnotsourbro). As I inderstand it, the conversion of diacetyl-->acetoin-->butandiol stimulates the activity of Brett due to this effect. Indeed, acetoin has been used in a number of publications to stimulate Brett to look at fermentstion patterns, etc. Sacch is not subject to this same type of regulation. So an argument could be made that Brett is better suited simply due to the stimulation that these compounds provide.

Additionally, it’s also worth thinking about is where the diacetyl is comin from- some of the LAB that produce diacetyl also produce polysaccharides thay can also be used by Brett. I’m not sure how well the composition of these polysaccharides has been studied (as it relates to beer production and Brett physiology and metabolism) but adding Brett to viscous beer (ie, viscous due to these polysaccharides produced by some LAB, sometimes referred to as "ropey" beer) decrease the viscosity much more rapidly than do Sacch strains. Lots of other possible explanations for that observation (pH tolerance, etc) of course.


Thanks, that’s interesting. That’s another reason I forgot which will make a difference to what brettanomyces will get up to if you co-pitch at the start of primary - it will get a bit of oxygen.

Another reason brettanomyces is good for cleaning up diacetyl is just the simple fact that it’s typically doing to be around and active longer than saccharomyces. If you’ve got peddiococcus in your beer, there’s some chance it will be active and producing diacetyl when saccharomyes has pretty much gone to sleep. If you’ve got some brettanomyces actively fermenting complex sugars at this point (and it will do this, for example, in lambic, much longer than pediococcus is active), it will probably be in a better position to clear up any remaining diacetyl than saccharomyces will.

There are other microbes around too that I’d be interested in knowing about. Debaryomyces seems to be more active for longer than I’d expected in lambic, as you can see in the graphs here: http://www.garshol.priv.no/blog/317.html . I wonder if that stuff clears up diacetyl in the same way, though that’s digressing from brettanomyces.

Though Frank Boon posts in the comments (cool!) saying the fermentation doesn’t look typical (excessive enteric fermentation).

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