Originally Posted by King of Cascade
Interesting…could you provide a link? It’s not that I’m challenging your findings but would like to do some research myself. I found Steve Piatz seminar to be very interesting at NHC and would like to learn more.
So my personal digging into literature turned up little to no discussion of lactic acid production by brett, what I found was related to the krebs cycle which is a normal metabolic pathway for bacteria and even you, however, this lead me to believe that there is no mechanism for lactic fermentation by brett, to further address this issue I contacted Chad Yakobson, who is a brewer with Odell, and who recent received a masters in brewing, his thesis was on brett fermentations this is what he had to say.....
"there is no direct texts which talk about lactic acid production. The main acids produced and transported out of the cells are acetic acid, capric acid, caproic acid and caprylic acid. The reason nothing exists on lactic acid is because it doesn't produce it in quantities that have any organoleptic impact. Most strains most likely form almost none. Acetic acid on the other hand is heavily produced in aerobic environments, and therefore has been heavily concentrated on in previous studies. How most of the studies concerning compounds with yeast occur is through observing esters and then looking at the production of the acid which made up part of that ester and looking for its origin. If Brettanomyces species produced lactic acid, it would have been written about academically already, but instead it has been shown that without exogenous additions of lactic acid, minute amounts of ethyl lactate are formed if at all.
In my study I observed ethyl lactate production in every fermentation. All the fermentations which observed pitching rate and no lactic acid addition had between .18 and 1.81 mg/l. When adding 100 mg/l between a 5 and 10 fold increase in ethyl lactate was observed. This trend continued all the way up to 3,000 mg/l which I observed too.
That data is what leads me to believe somewhere between 1 and 10 mg/l is excreted out of the cell during various metabolic processes. If you go and read up about the TCA cycle and then read about the activity of the EMP pathway in Brett and lowered amino acid synthesis during aerobic growth a spotty conclusion can be made that somewhere some is being produced through various steps and not fully consumed. But Brett does not lactic ferment, this is a whole different process, and as those pathways do not appear to exist in the genome and they have not been observed by previous researchers. Lactic acid is not produces by Brettanomyces the way a lactic ferment takes place in Lactic acid bacterias.
All this will be up on the site soon and you can read all about various pathways and secondary metabolites. But it takes time to get content up and converted for the web."