The Propionic-Acid Bacteria–a Review

Abstract

This paper, the second of three sections of a review, deals with propionate and acetate formation, carboxylation, decarboxyiation, and transcarboxylation, the roles of biotin and vitamin B12, and the enzymes involved in the propionic-acid fermentation. Pathways for propionate, acetate, and carbon dioxide formation by Propionibacterium have been thoroughly investigated and established. These investigations led to discovery of transcarboxylase, a biotin-containing enzyme, and were the result of studies showing that the formation of propionate does not involve the expected turnover of CO2. This enzyme appears to be unique to propionibacteria; it could be speculated that it is the first discovered of a group of transcarboxylases. One of the breakthroughs relative to the mechanism of biotin fixation reactions was the discovery that biotin can be carboxylated enzymatically.

Production of conjugated linoleic acid by dairy starter cultures

“…freundenreichii and shermani, respectively, were found to be capable of producing CLA from free linoleic acid. Propionibacteria are Gram-positive, short rods that grow under anaerobic conditions by using glucose or lactate as energy sources and produce propionic and acetic acid (Hettinga and Reinbold 1972). These organisms are important in several industrial applications, e.g.…”

Dairy Propionibacteria: Less Conventional Probiotics to Improve the Human and Animal Health

“…T h e subsequent period of warm room ripening is characterized by a marked growth of propionibacteria that metabolize the lactate produced by the lactic acid bacteria into propionate, acetate and CO2. At the end of maturation that ranges from 6 weeks to 12 -18 months in the hardest varieties, the number of propionibacteria reaches 10 8 -10 9 cfu/g of cheese [41,57].…”

“…Pyruvate is then oxidised to acetate and CO2 or reduced to propionate. The latter transformation occurs via the Wood-Werkman cycle or transcarboxilase cycle which represents the key component of the central carbon metabolic pathway in propionibacteria [41].…”

“…This microorganism synthesizes cobalamin as a cofactor for propionic acid fermentation [41] and is the only bacteria, among B12 producers that possess the GRAS status of the United States Food and Drug Administration.…”

“…Propionibacteria are heterotrophic microorganisms that mean they need an organic carbon source to grow and posses a fermentative metabolism [41][42][43]. They degrade carbohydrates like glucose, galactose, lactose, fructose and other sugars; poliols like glycerol; erythritol and others; and organic acids such as lactic and gluconic acids producing propionic, acetic and CO2 as the main fermentation end-products [1].…”