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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

PropionicacidBacteriaEnrichment

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 …

Brownish-redcoloredcolonies

Probablydue to having a cytochromesystem

CatalaseActivitytest:

Catalase

2H2O2 2H2O + O2

Production of O2 Bubbles


Propionic acid bacteria enrichment

Looking at them under the microscope…

Smallnon-motilerod-shappedbacteria


Propionic acid bacteria enrichment

Propionic acid formation

Dicarboxylicacidpathway:

NAD+

Lactate

LactateDehydrogenase

NADH

methylmalonyl-CoAmutase

Vitamin B12

Succinate


Propionic acid bacteria enrichment

Propionic acid formation

Acrylatepathway:

CoA-SH

CoA-SH

ThispathwayoccursnamelyinClostridiumpropionicum


Propionic acid bacteria enrichment

Propionic acid formation

Acrylatepathway:


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