Digestion

Autocatalytic Digestion

We will first assume the following:

1) digestion only occurs in the stomach.
2) it behaves as a CSTR.
3) nature operates at the optimum conditions which in this case means the rate in the stomach is at its maximum.

Derive

The reactor volume is then the area under the curve of the figure below.

If we assume the reactor volume and the mass flow rate are the same and the stomach operates as a PFR, we would obtain less conversion than the case of the CSTR, this is seen below.

In order to achieve the same conversion as the CSTR for the autocatlytic reaction, a much lager volume would be required.

We see that if autocatalytic digestion takes place only in the stomach the most efficient system to convert food into products (as in vitamins and nutrients) is the CSTR. This difference in efficiency is easily seen when the performance of a CSTR and PFR are graphed against each other with the autocatalytic reaction. Ideally, in the digestive system a maximum reaction rate is desirable. Thus, conversion will be kept low and a CSTR will be desired. Physiologically this is also true because within a stomach upon exiting the feed is acidified which inhibits the fermentation process, and enzyme catalytized digestion begins to take place in the intestines.