Saurkraut and Sourdough fermentation, and Lactic acid bacteria

WhWe are expecting to observe ecological susccession of the microbial community in our sauerkraut fermentations. Hat specific process or change is driving this succession?

Acid production and decreasing the pH

What is ecological succession ?

Change sin the species present within a community observed over time

What perserves saurkraut from spoilage?

High salt concentration and high acidity/low pH

Mature sourdough (flour and water) starters cpntain diverse population of "wild" yeasta and lactic acid bacteria mostly of what genus?

Lactobacillus

What does Lactobacillus produce that gives sourdough its distinct flavor?

Lactic acid

What is the major fermentation product of lactic acid bacteria?

Lactic acid

What are the gram results of lactic acid baceria and what are their morphology?

Gram postive rods or cocci

Lactic acid bacterium are catalase negative. Why is this weird and what do they use alternatively?

Because they are aerotolerant anerobes so they can grow in the presence of oxgyen. Alternatively, instead of using catalase to get rid of oxygen species like hydrogen peroxide they use a different enzyme, peroxidase.

Lactic acid bacterium are aerotolerant what?

Aerotolerant anaerobes which means they grow anaerobically but they can grow in the presence of oxygen.

What does it mean that lactic acid bacteria are fastidious?

They have a variety of nutritional requirements that must be met by their plant or animal hosts

WHat are homolactic fermentators?

Lactic acid bacteria that only produce lactic acid as the only fermnetaiton product (by oxidizing glucose to two pyruvate, then reduce that to lactic acid)

What are heterolactic fermentators?

Lactic acid bacteria that form CO2 and ethanol in addition to lactic acid (decarboxylate glucose --> 5 carbon sugar rublose 5 phosphate --> oxidize that sugar to one molecular of pyruvate + actetate = reduced to lactic acid + ethanol

After inoculating lactic acid bacteria to TSY/ glucose/ bromcresol purple deeps what will it look like after incubation if it produces lactic acid? And why do we add a layer of 3% agar?

It will turn yellow indicating lactic acid production and we add a layer of 3% agar to trap gas bubbles indicating CO2 production which heterolactic fermentators and not homolactic fermentators can do.