Why Do Micro Organisms Ferment Our Food

My boys always wanted to know how things work. Some folks are like that, even as adults. If you want to know the how’s and why’s of all the workings behind fermentation, Andrew is the guy to follow. In this post, he will explain why micro organisms ferment our food.

Have you ever wondered why yeast ferments bread to make sourdough?  Or why the grains of bacteria and yeast work together to ferment milk to make kefir?  Or even why our beloved SCOBY makes us the delightful drink we call kombucha?  Is it because they are all benevolent creatures who care for the health and gastronomic delight of us humans?  I mean, they selflessly work 24 hours a day, 7 days a week, without holiday breaks and never go on strike.  How much more altruistic can you get than that?  In this post, we are going to look at why micro organisms ferment food.

The truth is far from such a Utopian ideal.  The truth is, these micro organisms ferment food for themselves; they do it to live.

What are heterotrophs?

All of the organisms responsible for fermentation are what we call heterotrophs—a fancy-sounding science word made of two roots that give us a clue to its meaning.  The first root is “hetero” which means “other.” The second root is “troph” which means “nourish.”  When you put these two roots together you get “other nourish,”  and that gives us our clue.

Heterotrophs are organisms that get their nourishment from other living things; in other words, they can’t make their own food.  There are many different types of heterotrophs on this planet of ours: humans, cows and, yes, even the yeast in our beloved sourdough starter.  Yet even with such variety, all of us have something in common—our never-ending quest for food.

The Purpose of Food

But why do we need to eat food at all?  What is the purpose to eating food?  Humans eat food for many varied cultural reasons. But other forms of life only have two reasons—to obtain nutrients and to acquire energy.

Heterotrophs eat food in order to obtain nutrients.  We lump many things under this rather austere label of “nutrients,” but these chemicals are more varied than we can ever know.  Basically, nutrients are the building blocks of life.  Our physical bodies are put together using these chemical pieces.

Heterotrophs also eat in order to obtain energy.  While our physical bodies are made up of nutrients, energy is what gets these physical machines to run.  All forms of life run on the same chemical for energy—ATP (or, if you wanted to know, adenosine triphosphate).  Yet, all energy comes to the earth in the form of sunlight.  So the question is, how to go from sunlight to ATP?  Plants are the first step.  They take the energy in the sun’s light and put it into chemicals like sugar.  Heterotrophs then eat those plants, break down the sugar, capture the energy, and store it as ATP.

Bringing It All Together

So how does fermentation relate to all of this?  Well, fermentation is one method that heterotrophs use to break down sugar to capture its stored energy and make ATP!  The yeast and bacteria responsible for fermenting all of the products that we use on a daily basis ferment these foods in order to get energy.  Our sourdough starters get it from the wheat flour that we give it every day; our SCOBY’s get it from the sugar that we add to the tea; and the cabbage provides plentiful nutrients and energy to the lactic acid bacteria making our sauerkraut.

So, while they might not be quite as altruistic as we first thought, yeast and bacteria are still amazingly-designed creatures.  Sure, they are just trying live, but in their quest to survive, we can partner with them to make many a tasty treat.

Ferment on, my friends!


If you are new to fermenting, I suggest you start with a Fermentools Starter Pack. It has everything you need to do one batch of any of the recipes you find on this site. Need a recipe to get you started? Just click on the Recipe category in the sidebar.


Andrew and Michelle are the new owners of a 12-acre homestead in rural America.  They are just embarking on this journey that is far removed from their city-life upbringing, so they realize that they have a lot to learn in order to succeed in this new place.Come along with them and read more about what they learn as they make this transition at simplelifehomestead.com.

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