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Author: Subject: Isolation of Acetate and/or Malate ions with Electrolysis?
CocoMoco
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[*] posted on 20-6-2020 at 11:38
Isolation of Acetate and/or Malate ions with Electrolysis?


Is it possible to isolate acetate and/or malate using electrolysis? Essentially, I want to isolate the compounds without the hydrogen ion, calcium, sodium, potassium, etc. in association. Ideally, if they were alkaline or around pH neutral, that would be the best.

I have very unique goals in fermentation of molasses - I need to keep a pH constant of about 6 without invading the fermentor (this creates the best aroma and flavor with the yeast).

The yeast releases acetic acid as part of its normal metabolism which drops the pH. However, if a certain concentration of acetate is already present in the medium, the yeast will develop an equilibrium for absorption and release of acetate, causing the pH to stabilize. If I add the salts of acetate (such as calcium or sodium) that will negatively impact the yeast and its metabolism. I want to add in the acetate ion until I hit the optimal concentration for pH stabilization so that I don't need to constantly invade the fermentor and disturb fermentation kinetics.

Malic acid can also be converted by the yeast to ethanol, which can result in a pH increase.

The molasses is often around pH 5 naturally, so if I can help raise it to 6 without adding salts, that would be immensely beneficial.

If it is possible with electrolysis, can someone recommend the ideal equipment and setup for doing it?

Thank you!
~Cory
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DraconicAcid
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[*] posted on 20-6-2020 at 11:48


You can't isolate an anion without a cation. Period.



Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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violet sin
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[*] posted on 20-6-2020 at 12:23


Just a thought. Ion exchange resin? My water softener uses a salt brine bed to regenerate it's resin bed every night about "you should be sleeping-O-clock". I use that as a makeshift alarm to pack up the evenings adventure of whatever hobby/cleaning I'm up to. When the salts low, my water tastes like baking soda. Anyhow I was reading up on the process a few nights back so it was fresh in my mind. Forgive the rambling.

Mine exchanges sodium for magnesium and calcium but there are several kinds. Here are a couple leads I came up with for you maybe?

*****†*************
https://www.intechopen.com/books/new-trends-in-ion-exchange-...

DOI: 10.5772/intechopen.76879

Extractive Fermentation Employing Ion-Exchange Resin to Enhance Cell Growth and Production of Metabolites Subject to Product or By-Product Inhibition

..."The excessive accumulation of end-product/by-product in the culture may inhibit the growth of cell and represses the secretion of target metabolite. In the production of many fermentative products such as antibiotics, amino acids, and fungal metabolites, a serious problem of feedback inhibition is often encountered"

...."Hence, extractive fermentation via in situ ion-exchange-based adsorptive technique is a possible approach to be used industrially to mitigate feedback inhibition, aimed at enhancing fermentation performance"

************†***************
https://www.sciencedirect.com/topics/agricultural-and-biolog...



Extractive Fermentation for the Production of Carboxylic Acids

"2.2.1 Adsorption
Anion exchange resins have been widely studied for use as adsorbents of carboxylic acids, including lactic, citric, fumaric, and acetic acids [42–45]. In general, the undissociated acid is adsorbed onto weak or strong base polymer resins containing tertiary or quaternary amine groups, and the adsorbed acid molecules are later eluted or desorbed with methanol, ammonia, or H2SO4"

..."The main disadvantages of the adsorption process for carboxylic acid separation are its low adsorption capacity (usually less than 100 mg/g resin) and the requirement of additional chemicals for acidifying the feed broth and for eluting/desorbing the acid molecules from the adsorbents. The presence of other anions, such as SO42– and Cl–, in the fermentation broth can significantly reduce the adsorption efficiency due to competition"
..."Other materials, including activated carbon, polyvinyl pyridine, and Silicalite (Zeolite) molecular sieves, have also been studied for the adsorption of lactic acid [49, 50]. Compared to solvent extraction, adsorption is more expensive and thus has not been used in industry for carboxylic acid separation from fermentation broth."

******************

Perhaps a bed of exchange resin could be suspended in the fermenter chamber partially loaded already? This is not my field of expertise... I've not really one anyhow. But a shot in the dark. I know the articles were about different fermentations but maybe the resin is still useful. Elution after you batch is done will keep extra chems out of your process.


[Edited on 20-6-2020 by violet sin]
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wg48temp9
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[*] posted on 21-6-2020 at 09:57


Quote: Originally posted by DraconicAcid  
You can't isolate an anion without a cation. Period.


It could be done by negatively charging up a Leyden jar filled with acetic acid. The charging being done via an acetic acid bridge. Some of the hydrogen ions would be extracted out by the voltage via the bridge and be discharged at the electrode at the end of the bridge.

If the Layden jar has a capacity of 1nF and is charged to 50,000V , I estimated it would contain on its inner surface about 30ng of acetate ions.

If you manged some how to transfer the 30ng of acetate ions to a spherical flask of 100mm in diameter which has a capacity of about 5pF it would have a voltage of 10 million volts.

So D-acid is correct its very very impractical.

PS: I was curious just how impractical collecting acetate ions would be.




i am wg48 but not on my usual pc hence the temp handle.

Thank goodness for Fleming and the fungi.
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violet sin
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[*] posted on 21-6-2020 at 14:14


So I've a question. Why leave the acidic proton in solution if you want the pH to rise some? Your starting at pH of 5, fermentation gives acetic acid driving pH down lower... Taking the acetic acid whole, would reduce acidity = run the pH up towards your 6 region desired for flavor. The second reference I linked had this...

"In general, the undissociated acid is adsorbed onto weak or strong base polymer resins"

No you can't take half, it takes them protons and all, but why is that a problem. it would seem this either sequesters acetate till it's full or overrun with other acid species. Either way the mix would tend towards higher pH as acidic species were mopped up.

What is your target product? Alcohol?
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