I have a cell-free solution of culture broth. It contains a wide range of compounds ranging from salts (marine broth), lipids, and proteins to polysaccharides.

My goal is to extract all type of saccharides and lipids in order to concentrate an eventual bio-surfactant produced by my cells. I'm specifically interested in those composed of saccharides and lipids linked together (e.g. glycosidic bond).

It was suggested to me to use ethanol to precipitate out these polysaccharides. I have seen this done widely in the literature.

However, I would like to understand the chemistry of this process in order to understand what is actually precipitating out (just polysaccharides, monosaccharides? proteins? lipids?). And whether it will work for both lipids bound to polysaccharides, given that lipids are soluble in ethanol.

  • 1
    $\begingroup$ Even solubility of well soluble sucrose (table sugar) in ethanol is just 0.6 g/100 mL. $\endgroup$
    – Poutnik
    Jun 25 at 8:38
  • $\begingroup$ I’m pretty sure it’s primarily due to disruption of h-bonding with water which results in h-bonding between saccharides. Obviously more of an effect the larger the molecule. $\endgroup$
    – Andrew
    Jun 26 at 15:58
  • $\begingroup$ Well, you better thouroughly edit the post if you don't wanna waste the bounty. Body says very different story then title. $\endgroup$
    – Mithoron
    Jun 28 at 22:32
  • $\begingroup$ I don't see how the title is misleading. I seem to understand the biochemistry of ethanol precipitation. The body of my question just gives context as to why in case that helps focus the answer. $\endgroup$
    – donkey
    Jun 30 at 3:20
  • $\begingroup$ Surfactants in low concentration may be difficult to precipitate, as they are adaptive. I suppose the best would be doing separation experiments with isolated, compound class examples. What proteins do, what lipids do, what sacharides do, what liposacharides do, what their mixtures do. Because your sample may be a wild mixture with unclear interference. $\endgroup$
    – Poutnik
    Jul 7 at 7:15


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