As far as I could gather the digestion relies on enzymes which in turn set requirements for pH.

Is it possible for an alien creature to have a different set of enzymes that require basic environment and use lye as a base to provide such environment?

I suppose it would also need different mucus to protect its stomach from digesting itself.

The creature in question lives in earth-like environment in caves. It has slow metabolism so it does not need a lot of food. It's food mostly consists of remains of other dead animals. It can also scrape some minerals from the cave walls if it's useful. When threatened it produces toxic gas to protect itself. Digestion process can be very slow.


I looked up more info about mucus and it seems that soap that is created when fats mix with lye should not be much of a problem as mucus is a gel, not oil.

Though the process of digesting lipids remains messed up.

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    $\begingroup$ Digestive systems have varied PHs - exempli: the mouth is alkali, the stomach is acid, the small intestine alkali again - in humans. Each digestive system would be suited to the particular food, and the particular requirements of the organism. Could you please be specific about the requirements of your organisms in your world? $\endgroup$ – Measure of despare. Jun 15 at 4:44
  • $\begingroup$ Saliva is actually usually slightly acidic; I think you are thinking of the intestines. They have a Ph of 7.5. $\endgroup$ – Bilbo Baggins Jun 15 at 5:08
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    $\begingroup$ @BilboBaggins Not so, salivary amylase works only in an alkaline environment, there are acids and alkalis further on in the gut that allow enzymes to work there in specific ways according to PH. $\endgroup$ – Measure of despare. Jun 15 at 5:43

In principle it should be possible, providing that you have the suitable enzymes, however one of the possible problems I foresee with such a setup is saponification:

Saponification is a process that involves conversion of fat or oil into soap and alcohol by the action of heat in the presence of aqueous alkali (e.g. NaOH). [...] Vegetable oils and animal fats are the traditional materials that are saponified.

Soaps have the properties of being both water soluble (with the polar part of their molecule) and fat soluble (with the non polar part). This might complicate the digestion process.

Another possible problem might be some interference with the Sodium usage in cells/muscles. Simplifying that the only salt an organism assumes is NaCl, while using Chloridric acid for digestion uses Cl iones for the acid and leaves Na iones for the cells, rerouting those Na iones to the digestion leaves you with a large amount of Cl iones that need to be either used or removed.

All in all, to make it possible you would probably start again from scratch with the chemical paths in the cell biochemistry.

  • $\begingroup$ Removing Cl through emitting gas would be perfect. Though the soap messing up mucus sounds like a problem. $\endgroup$ – MadCake Jun 15 at 7:05
  • $\begingroup$ Saponification appears to be the solution, not the problem at all. Part of the problem with fats is that they are not water-solvable, which is a problem for watery animals like us. But alcohols and soaps are water solvable, which makes them far easier to absorb by the guts of this hypothetical animal. We humans need a special protein to absorb the fatty acids. $\endgroup$ – MSalters Jun 20 at 13:17

Not the same way. The acid is not what is actually doing most of the digesting of the food; it is an enzyme called pepsin. The reason the stomach is acidic is pepsin works optimally at a Ph of 2. According to Wikipedia, pepsin is "inactive at pH 6.5 and above", meaning that a base would be detrimental to digestion.


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