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FermentationExplainer

Fermentation as a Living Process

Fermentation is not one reaction performed by one organism. In many foods it is a changing ecology in which microorganisms transform both the material and the conditions for the next stage.

MICROBA8 min readAugust 19, 2026Revision 2
FermentationFood MicrobiologyLiving SystemsMicrobial Succession

Fermentation leaves visible traces.

Aroma changes.

Acidity changes.

Gas may appear.

Texture can change.

But the deeper transformation occurs within a microbial ecology.

Fermentation is metabolism in context

At the cellular level, microorganisms use metabolic pathways to obtain energy and transform molecules.

At the community level, those transformations accumulate.

Sugars become acids, alcohols, gases and other metabolites. Proteins and complex carbohydrates can be broken into smaller compounds. One organism's product can become another organism's substrate.

The material being fermented becomes a changing habitat.

Communities succeed one another

Spontaneous fermentations often show microbial succession.

The organisms detected early in the process may not be the same organisms that dominate later.

Why?

Because the environment changes.

Acidity can rise or fall. Available sugars decline. Salt and water activity exert selective pressure. Oxygen can be consumed. Metabolites accumulate.

The organisms that perform early transformations help create the habitat experienced by later organisms.

The process has memory

Fermentation is also shaped by what came before.

Back-slopping in sourdough, for example, deliberately carries part of one fermentation into the next. Long-term studies show that particular strains can persist across repeated propagation when transmission and conditions remain suitable.

Other fermentations depend more strongly on organisms arriving from ingredients, equipment or the environment.

History becomes part of the ecology.

Conditions influence succession

Temperature can change growth rates and competition.

Ingredients can alter nutrients and microbial sources.

Water activity and salt can restrict some organisms more strongly than others.

This is why two fermentations that begin with similar ingredients may not develop identically if their conditions differ.

A living process responds.

Fermentation is not automatically beneficial

The word fermentation is sometimes treated as a synonym for "healthy" or "safe."

That is scientifically inaccurate.

Fermentation is a broad class of microbial and biochemical processes. Desirable food fermentation depends on appropriate organisms, conditions, hygiene, process control and intended use.

An uncontrolled microbial change is not validated simply because it produces bubbles, acidity or aroma.

What we know

Research on fermented foods supports that:

  • microbial communities often change predictably through stages;
  • microorganisms modify the conditions of the food environment;
  • temperature and ingredients can alter community succession;
  • repeated propagation can maintain particular microbial lineages;
  • metabolites reflect both community composition and environmental conditions.

What remains uncertain

Many traditional fermentations contain complex communities that differ between locations and batches.

Sequencing can reveal which organisms are present, but presence does not always identify the organisms responsible for a particular metabolite. Controlled experiments are needed to move from correlation to mechanism.

MICROBA Perspective

MICROBA sees fermentation as a living process because the system is continuously becoming something new.

Organisms respond to the habitat.

Their activity changes the habitat.

The changed habitat selects what can happen next.

This is continuation through transformation.

Fermentation is not merely waiting. It is life changing the conditions of life.

References

  1. Wang X, et al. Unraveling microbial community diversity and succession of Chinese Sichuan sausages during spontaneous fermentation. Journal of Food Science and Technology. 2019. https://pmc.ncbi.nlm.nih.gov/articles/PMC6582033/
  2. Kim J, et al. Impact of essential and optional ingredients on microbial and metabolic profiles of kimchi. 2024. https://pmc.ncbi.nlm.nih.gov/articles/PMC11016982/
  3. Liu Y, et al. Temperature-Induced Annual Variation in Microbial Community Changes and Resulting Metabolome Shifts in a Controlled Fermentation System. mSystems. 2020. https://pmc.ncbi.nlm.nih.gov/articles/PMC7566281/
  4. Galle S, et al. Does strain-level persistence of lactobacilli in long-term back-slopped sourdoughs inform on domestication of food-fermenting lactic acid bacteria? 2024. https://pmc.ncbi.nlm.nih.gov/articles/PMC11654800/