It is becoming increasingly recognised that the role of bacteria in digestion is, from the clinical standpoint, a much more important one than formerly supposed. Active bacteria are numerous in the alimentary canal. These include: - Bacteria, spores of fungi, yeasts, sarcinae.
Since many bacteria can break up carbohydrates, and also proteins, in a manner similar to that of the intestinal ferments, it is admittedly difficult to say where pancreatic digestion ends and bacterial activity begins. The chief points of importance in regard to bacteria and their action in digestion are as follows.
Lactic acid bacilli of many kinds are introduced with the food. These make lactic acid from cane sugar and milk sugar as follows: -
C6HI2O6 = 2C3H6O3
C12H22O11 + H2O = 4C3H603
There are also several varieties of butyric acid forming bacteria in the alimentary tract. These change lactic acid and cane sugar into butyric acid, hydrogen, and carbonic acid. Yeasts change dextrose (grape sugar) into alcohol, succinic acid, and glycerine; and the Mycetoma aceti and other bacteria convert carbohydrates and alcohol into acetic acid, carbonic acid, and water, and also change acetates into carbonic acid and carbonates. It has to be noted that the organic acids produced by decomposition of carbohydrates inhibit or reduce the activity of the putrefactive bacteria.