Propionates, Propionic Acid

Propionate, also known as propanoate, propionic acid, ethylformic acid, and methylacetic acid, is a type of short-chain fatty acid (3-carbon saturated monocarboxylic acid). Propionates can be obtained from wood pulp waste by fermentation process using bacteria of the genus Propionibacterium, or from ethanol and carbon monoxide using a boron trifluoride catalyst, or by oxidation of propionaldehyde, and by many other methods 7.

In ruminant animals, such as cattle and sheep, the ingested food undergoes extensive fermentation in the rumen, a large digestive organ containing cellulose-digesting bacteria and protozoa. Major products of the rumen fermentation include acetate, propionate, and butyrate. Propionate is an important source of energy for these animals.

Propionates are used in the food and feed industry as preservatives. They are also used for the production of various plastics, pharmaceuticals and perfumes. Propionic acid derived from fermentation is produced primarily by Propionibacterium bacterial species. Calcium propionate is used in bakery products as a mold inhibitor, but unlike benzoate, it does not require an acidic environment. Sodium propionate is also used as an antifungal agent 1. Sodium propionate at levels 0.1% to 5% delays growth of S. aureus, <Sarcina lutea, Proteus vulgaris, L. plantarum, Torula species, and L. ellipsoideus by 5 days. It postpones spoilage in fresh fruits and vegetables having neutral pH.

Graphic representation of propionic acid, propionate

The principle metabolites of fermentable fibers are lactate and short-chain fatty acids (SCFAs), formerly called volatile fatty acids because of their volatility in acidic aqueous solutions. SCFAs are produced by microbiota in the colon and the distal small intestine from resistant starch, dietary fiber, and other low-digestible polysaccharides. Different fibers are fermented to different SCFAs in different amounts by different bacteria. For example, ingesting pectin results in higher propionate concentration in the colon of rats than ingesting wheat bran. Some general effects of SCFAs include 8:

  • increased water and sodium absorption in the colon
  • mucosal cell proliferation
  • provision of energy
  • acidification of luminal environment

It is well established that supplementing resistant starch and dietary fibers in diet, which raises intestinal and circulating short-chain fatty acids, confers metabolic benefits in humans. Recent animal studies have also shown that propionate suppresses food intake, protects against high-fat diet-induced weight gain and glucose intolerance, and stimulates gut hormone secretion 4,5.

Antitumor Properties

Short-chain fatty acids, particularly propionate and butyrate, are well-known for their antitumor effects toward colon cancer via apoptosis, a natural physiologic process allowing depletion of cancer cells. Cancer cells fragment in a coordinated chain reaction and the residues are absorbed by adjacent tissues and immune system cells. Dairy propionibacteria are able to produce beneficial pro-apoptotic SCFAs and they may prove useful in cancer prevention or treatment6.

References

  1. Nurhan Turgut Dunford (editor). Food and Industrial Bioproducts and Bioprocessing
  2. David E. Metzler, Carol M. Metzler. Biochemistry: The Chemical Reactions of Living Cells, Volume 2
  3. P. Michael Davidson, John Nikolaos Sofos, Alfred Larry Branen. Antimicrobials in Food
  4. Short-chain fatty acids induced autophagy serves as an adaptive strategy for retarding mitochondria-mediated apoptotic cell death
  5. Butyrate and Propionate Protect against Diet-Induced Obesity and Regulate Gut Hormones via Free Fatty Acid Receptor 3-Independent Mechanisms
  6. Milk Fermented by Propionibacterium freudenreichii Induces Apoptosis of HGT-1 Human Gastric Cancer Cells
  7. PubChem Substance
  8. Sareen S. Gropper, Jack L. Smith, James L. Groff. Advanced Nutrition and Human Metabolism