The Transformative Fungus That Powers Japanese Cuisine

A single mold is behind many best-known flavors.

A brew master adds Koji bacteria powder to steamed rice in order to make sake.  (Buddhika Weerasinghe / Getty)

It’s impossible to imagine Japanese meals without soy sauce, or the umami-rich fermented bean paste called miso, or the rice-based spirit known as sake. Which means that Japanese cuisine depends on the one fungus that enables the fermentation of all these delicious foods: koji. Today, American chefs are discovering what Asian cooks have known for centuries, that koji is a microbial powerhouse with seemingly magical abilities to completely transform food. But how does a mold from a family of microbes known for their toxicity turn salty, mashed beans into sticky, succulent miso? How did koji make its way from Japan to the U.S.? And how might the weird and wonderful ways chefs in the U.S. are now using koji transform the American dinner table, too?

Koji, or, as it’s known in scientific circles, Aspergillus oryzae, was domesticated by humans around 9,000 years ago. The fungus’s closest relatives can be deadly, due to the chemicals they produce to kill off microbial competitors. But, fortunately for our taste buds, a random nontoxic mutation likely landed on some damp leftover grains in Asia, and humans noticed that the fuzzy mold, with its intoxicating scent of grapefruit and flowers, also turned those grains into a literally intoxicating drink. (Our ancestors wouldn’t have known that this happened because koji broke down the starch enough to let yeast ferment the newly freed sugars into alcohol, but they’d have enjoyed the results.) Delighted, they probably encouraged the mold to grow on other left-over grains, gradually domesticating it by giving it a cushy home and caring for it over generations.

And they’d soon have realized that koji could could be used for more than making booze. Mixing the koji-furred rice, rich with protein-destroying enzymes, into beans breaks those beans down into the funky, fermented pastes that are staples in both China and Japan. Evolutionary genomicist John Gibbons, who studies koji’s domestication at Clark University, told us that as early as the 13th century in China, “there are advertisements that are selling what’s called moyashi. This is koji. So five, six, seven hundred years ago, before we knew what microorganisms were, we were selling them.”

Koji is something of a celebrity in Japan, where fans can buy koji cell phone charms, read koji-focused manga, and celebrate the microbe on October 12, a.k.a. National Fungus Day. But, although it was the subject of the first biotech patent ever granted in the U.S., in 1894, it has not caught on outside of Asian cuisine. Until now. Recently, a small handful of American chefs have discovered koji’s superpowers, and are using it to aerate whole-grain bread, transform kitchen scraps into complex sauces, re-invent fried chicken, and even cure meat. Listen in now to find out why koji seems to turn everyone it meets into obsessives, how its journey from East to West involves whiskey, arson, and cherry blossoms, and why it might just be next big thing in American cuisine. You heard it here first!

This article appears courtesy of Gastropod.