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Propionic acid Bacteria Enrichment. Bruno Fonseca Hopkins Microbiology Course 2010 Monterey , CA, USA .

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Propionic acid Bacteria Enrichment

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Propionic acid bacteria enrichment


Bruno Fonseca

HopkinsMicrobiologyCourse 2010

Monterey, CA, USA

Propionic acid bacteria enrichment

  • Propionic acid has numerous applications in various food and chemical industries, and is mainly used as a mold inhibitor for animal feeds and as a preservative for foods such as cheeses and baked goods.

  • Propionic acid is produced mainly by Propionibacterium, but this isn’t the only genera that has this ability:

  • Propionibacteriumare slow-growing, non-sporeforming, rod-shaped, Gram-positive, anaerobic heterotrophic bacteria.

  • These microorganisms usually possess catalase.

  • Ferment lactate and produce acetate, propionate and CO2.

  • If pH value is below 4.5 there is practically no growth

  • Clostridium

  • Veillonella

  • Selenomonas

Propionic acid bacteria enrichment

  • First observed in the cheese manufacture, dating back to the beginning of the nineteenth century.

  • Propionicacid is what partly gives Swiss cheese its characteristic flavor and the CO2 is what produces its characteristic holes.

  • Propionibacteriumhave been granted GRAS (Generally Recognized As Safe) status by FDA.

  • However, certain species of Propionibacteriumare known for causing infections including the common skin disease acne vulgaris (caused by P. acnes).

  • van Niel named some species of Propionibacterium.

Propionic acid bacteria enrichment

Day 1

  • Inoculum:

  • Swiss-cheese

  • Media:

  • 40 gr Sodium-lactate

  • 5 gr Yeast extract

  • Selective technique:

  • Lactate as the major carbon/electron source

  • Anaerobic growth (screw capped tubes gently bubbled with CO2)

  • Incubate at 30 ºC

Propionic acid bacteria enrichment

2 days later …

  • Streakedthemilk-whitegrowthinto a lactate-CaCO3agarplate

  • Incubatedat 30ºC inananaerobicjar

Propionic acid bacteria enrichment

1 week later …


Probablydue to having a cytochromesystem



2H2O2 2H2O + O2

Production of O2 Bubbles

Propionic acid bacteria enrichment

Looking at them under the microscope…


Propionic acid bacteria enrichment

Propionic acid formation







Vitamin B12


Propionic acid bacteria enrichment

Propionic acid formation





Propionic acid bacteria enrichment

Propionic acid formation


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