We humans have been treasuring and using microbial “trash” for tens of thousands of years. We eat and nurture microbes for their waste products – yes, you eat microbial poop. Metabolic by-products or “waste” would be more appropriate to say in a classroom/polite company, but really – it’s just “poop”.

Yogurt, sauerkraut, buttermilk, kefir, bread, beer, wine, cheese, even chocolate, and coffee – are all tasty to us because microbes have eaten the sugars in milk or some plant part. With the exception of corn, whatever you eat goes into your mouth in one form and comes out the other end in a totally different form. Same with microbes.

Bacterial Poop: Sugars to Lactic Acid

Bacteria like Lactobacillus sp. eat lactose milk sugars and poop out lactic acid. That’s why unflavored, unsugared yogurt is tangy and slightly sour. Same thing with the buttermilk I’ve been culturing recently. YUMMY. Other Lactobacillus sp. eat plant fiber sugars and poop out lactic acid to make sauerkraut and kimchee. Check out a yogurt experiment my girls and I did a while ago. Yes, the girls roll their eyes when I say that they are eating microbial “trash”.

microbe trash
Super YUMMY home cultured buttermilk is now a staple in our house.

Fungal Farts: Sugars to alcohol and carbon dioxide

Fungal microbes like yeast, Saccharomyces sp., eat sugars in flour or fruits and poop out alcohol. Saccharo = sugar; myces = fungi. These fungi have been friends with humans for ages [1]. If you enjoy yeast-breads, the alcohol and carbon dioxide are the gaseous “trash” given off when Saccharomyces cerevisiae eats wheat sugars. So actually, the lift in bread is due to fungal farts. tee he he he he.  There are tons of fabulous bread recipes out there and making yeast breads from scratch is pretty easy, but I LOVE the idea behind Magical Microbes DoughLab kit.

microbe trash
It’s a race to see which glove is inflated the fastest by the fungal farts! GIF courtesy of Magic Microbes

With the simple “wave of a hand” you and the kids can see that gases are given off when yeast bread dough is rising. With the instructions and kit ingredients, I’d think parents nervous about baking bread might give it a try. I haven’t tested this specific kit yet, but Magical Microbes is an excellent resource for science experiment kits for kids or classrooms.

Bacterial Poop: Sugars to Electricity

Although microbial “trashed” foods may not be new to you, what about soil microbes that poop electricity? Stay tuned for the next post on soil microbes like Geobacter sp.  which give off electrons when they feed on sugars. Fungi have a roll in this “shocking” system too. I’ve played a lot with the MudWatt kit and given it to other parents to try. If you need a neat way to demonstrate the power of microbial poop to our human world – check out Magical Microbe’s KickStarter Gold campaign.

  1. Legras, J.-L., et al., Bread, beer and wine: Saccharomyces cerevisiae diversity reflects human history. Molecular Ecology, 2007. 16(10): p. 2091-2102.

Other Farty posts:

Bacterial Farts – Whoopie! 

Microbial Trash Part II  – energy from bacterial poop

Brain’s On Podcast: Farts Smarts: Understanding the Gas we Pass

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2 thoughts on “Microbial “Trash” is Human Treasure

    • June 23, 2017 at 12:31 pm

      Wow – thanks – that means a lot coming from such a talented microbial educator and advocate as yourself!


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