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Chemgineer
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[*] posted on 1-8-2023 at 13:10
Lactic acid


I see videos on Youtube about producing LAB (lactic acid bacteria) from fermented rice wash water and cows milk.

Is there a route to take that LAB and produce some lactic acid that could be distilled to a good concentration?

[Edited on 1-8-2023 by Chemgineer]
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RustyShackleford
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[*] posted on 1-8-2023 at 16:48


Extracting lactic acid from any sort of complex aqueous mixture sounds like a huge PITA, especially if you're using non-engineered LAB. if you insist on making it, why not hydrolyse some PLA plastic?
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Johanson
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[*] posted on 1-8-2023 at 21:50


Interesting problem. Apparently not easy to separate from water via distillation due to its affinity for water. PPT and/or fractional crystallization is common lab approach, anyway.
Some quick reading:
https://bioresources.cnr.ncsu.edu/wp-content/uploads/2017/04...
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teodor
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[*] posted on 2-8-2023 at 00:36


I think the approach could be to form a lactate complex with some transition metal and to separate the acid in this form.
Update: actually there is no big choice. The acid in its free form forms complexes with copper and zinc only.
https://en.wikipedia.org/wiki/Copper(II)_lactate
https://en.wikipedia.org/wiki/Zinc_lactate




[Edited on 2-8-2023 by teodor]
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clearly_not_atara
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[*] posted on 2-8-2023 at 04:28


There's also definitely a titanium lactate complex, though idk how it could help isolate lactate.



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KoiosPhoebus
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[*] posted on 2-8-2023 at 11:18


Aluminum forms a stronger complex with lactate anions than copper or zinc (log K for Al3+: 5.8, log K for Cu2+: 2.47, values from NIST SRD 46 stability constant database), so if you're attempting to solubillise the lactate, that might be one way to go.

Alternatively, you could use calcium hydroxide to react with the lactic acid and precipitate low-solubility calcium lactate. Then use sulphuric acid to liberate lactic acid while calcium sulphate is precipitated out.

It's an interesting project, but if you need lactic acid for any purpose, it would be way easier to just buy it. Brewing supplies places typically have some as pH adjuster.
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Johanson
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[*] posted on 2-8-2023 at 14:31


From "Industrial Chemistry", sorry for the quality:

"Lactic acid is formed by the action of Bacterium lactis
ii on molasses or other sugar-containing material. After dilution, chalk
dded, and a nutritive solution, and the action allowed to take place at
to 45° C. (104° to 113° F.) ; the chalk is acted on by the lactie acid as
_ as formed, and carbon dioxide given off:
2CH:CHOHCOOH + CaCO; = (CH:CHOHCOO).Ca + CO. + H2O.
» chalk must be added because the bacteria become inactive if the contration
of the acid is allowed to rise above 1 per cent. The calcium
ate precipitates and is filtered, washed, and treated with dilute sulfuric
1 which liberates the lactic acid in solution form. The calcium sulfate
ltered off, the solution of lactic acid clarified, and concentrated to 50 per
t lactic acid, a thick solution. Pure racemic lactic acid melts at 18° ee
» 50 per cent solution is used in textile plants, and, especially purified,
ertain foods."

So you PPT the steadily-forming acid by using CaCO3, then pH adjust the Ca lactate with sulfuric acid, then PPT the CaSO4 which results, then render the lactic acid down to a thick 50% goop. After that, I assume you need vacuum distillation or very careful crystallization. So when can we see some pictures, Chemgineer?
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teodor
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[*] posted on 4-8-2023 at 00:01


Probably zinc and copper lactates have convenient solubilities for separation.
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UC235
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[*] posted on 4-8-2023 at 13:59


Sodium lactate 60% aqueous solution is a cheap and available soapmaking chemical. You might be able to buy lactic acid itself as a questionable DIY chemical peel material. Ethyl lactate is (though I haven't looked in years) available as a "green" paint remover solvent.
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