Bacteria are found everywhere. They can also grow on various substrates. Are there any bacteria that can be used as a food source? For example mix x with water and add some of these bacteria. These then either turn x into something nutritious or can be consumed themself. Are there any potential candidates? Bonus points if the substrate bacteria use to grow is abundant.
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$\begingroup$ I think the catch might be nutritional density. Remember what happens when bacteria get too concentrated in brewing: They die out like in brewing alcohol. $\endgroup$– DKNguyenCommented Jun 9, 2022 at 13:37
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9$\begingroup$ Does yogurt count? Beer? Other fermented foods? $\endgroup$– Bryan Krause ♦Commented Jun 9, 2022 at 16:48
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$\begingroup$ I was rather thinking about something abundant but not nutritious themself.Are there any examples with wood / cellulose? $\endgroup$– CuriousIndeedCommented Jun 9, 2022 at 21:58
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1$\begingroup$ en.wikipedia.org/wiki/… $\endgroup$– Nilay GhoshCommented Jun 10, 2022 at 4:07
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1$\begingroup$ @DKNguyen The die-off in uncontrolled beer fermentation is due to the alcohol produced by Saccharomyces cerevisiae, which is a yeast, not a bacteria. $\endgroup$– MattDMoCommented Jun 10, 2022 at 14:14
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5 Answers
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The best example of bacteria-as-food is the genus Arthrospira, which is a kind of cyanobacteria whose edible biomass is known as spirulina.
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$\begingroup$ I didn't realize algae were classified as bacteria. $\endgroup$– DKNguyenCommented Jun 9, 2022 at 20:28
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20$\begingroup$ @DKNguyen Somewhat confusingly, cyanobacteria are both known as "blue-green algae" and also not really considered algae. Algae in general as a term is highly non-specific. $\endgroup$– Bryan Krause ♦Commented Jun 9, 2022 at 20:47
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2$\begingroup$ If consuming spirulina, note that spirulina can be easily contaminated with other algae's toxins, and that spirulina should be avoided as a vitamin B12 source as its B12 bioavailability is questionable. $\endgroup$ Commented Jun 12, 2022 at 15:05
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From the comments:
I was rather thinking about something abundant but not nutritious themself. Are there any examples with wood / cellulose?
In fact, the traditional Filipino food called nata (examples of which include nata de coco and nata de piña) are basically cellulosic pellicles of the bacterium Komagataeibacter xylinus, produced by culturing the bacterium in the appropriate medium (coconut water for the former, and pineapple juice for the latter).
(This resembles the SCOBY that is used in making kombucha.)
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While not used as a food per se, bacteria are used in production of many foods, and you eat masses of them when consuming the product. At a guess; in the 10's of millions per bite is my estimate.
One type that is commonly used in several sorts of foods are the Lactobacilli. These are commonly used to generate sour products, through their fermentation of sugars into lactic acid. They are used extensively in yogurt production (Lactobacillus acidophilus usually), as well as other fermented diary products (cheese, kefir, cream cheese, sour cream, etc.) sourdough breads, production of fermented pickles such as sauerkraut and kimchi.
In some cases, such as kimchi and sourdough, these are often the natural lactobacilli and other bacteria and yeasts that are on the material used to make the product, so no added culture. In the case of sourdough, the fermentation can also be a result of yeasts in addition to the lactobacilli.
Similarly, acetic acid bacteria (Acetobacteraceae) are used in the production of vinegars, though in most cases these are filtered out before selling, so you don't generally consume them.
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Apart from the classical microbial food processes, there is also a more recent approach captured under the term "single cell protein" (https://en.wikipedia.org/wiki/Single-cell_protein). Basically microorganisms are grown on a suitable substrate, and the protein that makes up their cells is used as food. Typically it would be either a food supplement or used in animal feed.
Regarding bacteria, it's most interesting to look into autotrophs, which can fix carbon from CO2 with a source of energy, or methanotrophs, which grow on methane derived from natural gas or biogas.
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$\begingroup$ Additionally, there are efforts to use methylotrophic (which eat methanol or methane) organisms as sources for protein. In the future this might be particularly interesting because methanol and methane can be produced renewably from CO2, water and renewable energy. See e.g. solarfoods.com (I'm not affiliated with them). $\endgroup$– DahlaiCommented Jun 22, 2022 at 8:17
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Basically all the mammals which eat a diet comprising hard-to-digest plants like grass, scrub, etc. use bacteria exactly like this. So cows, horses, deer, camels, goats, koalas, and so on. They either use foregut fermentation (like cows) or hindgut fermentation (like horses). In either case microbes, including bacteria, break down hard-to-digest carbohydrates like cellulose into easy-to-digest simple sugars.
For some foregut fermenters like ruminants (e.g. cattle), gut microbes (including bacteria) are also an important protein source--the cow gut is split up into multiple sections, the first section (the rumen) is a comfortable place for microbes to live and break down cellulose but some of the microbes end up traveling with the food into another section where the microbes themselves are also directly digested by the cow.
Even humans have some bacteria which do this in a limited fashion, just not as efficiently as grazing animals.
Bonus side note: This does not include panda bears. Panda bears eat specific parts of bamboo which are easy to digest and high in protein already and their digestion functions much more like that of a carnivore.
