In a broad sense, fermentation is the transformation of food or raw ingredients into something beneficial for humans brought about by microorganisms (whereas spoilage is the version of this phenomenon that is harmful to humans). Just as alcoholic fermentation using yeast has given us wine and beer, and lactic acid fermentation using lactic acid bacteria has given us yogurt and pickles, fermentation is something that was discovered by chance and has developed throughout the long history of humankind. Back when I was doing agricultural research during my student days, I sometimes had vague ideas about the possibility of using microorganisms other than those generally known, as long as the same kind of fermentation was achieved.

It took another fifteen years until that youthful intuition came to fruition over the course of various coincidences and encounters, with the result that I was the first person in the world to discover that nutritious mushrooms have fermentative ability (that is, the ability to trigger food fermentation). The catalyst was taking up my current post at Mukogawa Women’s University. Something else came first, though: initially, I was researching functional foods that are effective at preventing cancer and thrombosis (myocardial infarction, cerebral thrombosis, and so on), which are the leading causes of death in Japan. As measures to prevent thrombosis, previous studies had recommended consuming foods that contain: firstly, fibrinolytic active substances, which dissolve blood clots; secondly, antithrombin-active substances, which make blood clots less likely to form; and thirdly, antioxidant active substances, which make thrombosis less likely to develop. At Mukogawa Women’s University, I conducted wide-ranging research into vegetables, fruits, and microorganisms. From that, I discovered that mushrooms contain these three substances, and then developed new foods utilizing them.

The first thing I did in my lab was to make a very simple prototype mushroom bread. Based on a student’s suggestion that it be something that all ages can enjoy, I took mushroom powder that had been ground in a blender and mixed it into the dough, and then baked it in a fully automatic bread maker. My curiosity was sparked when the bread did not rise very much for some reason. I observed the fermentation in a beaker and confirmed that adding mushrooms causes the dough to rise too quickly, resulting in holes on the surface and deflating it. This got me wondering about the cause and implications. With growing anticipation, I steered my research in a whole new direction, and eventually proved that mushrooms (maitake, oyster mushrooms, enoki, and so on) contain enzymes involved in various kinds of fermentations, including alcohol dehydrogenase, which causes the fermentation of bread and alcoholic beverages. To wit, I made a new discovery: you can make fermented foods with mushrooms. Moreover, I also discovered that the three thrombosis-preventing substances mentioned above are newly produced over the course of fermentation. Truly, you never know what will inspire or trigger your research.

Mushroom research was dominated at the time by the discovery of new species and their cultivation and breeding, and what I found seemed to shock and amaze many distinguished professors. The same could be said for the millennia-old history of fermented foods and the fermentation industry as a whole. Look back now, I fondly remember how the first academic journal I submitted to rejected my findings as impossible.

On the following pages, I would like to introduce some examples of functional fermented foods that we have developed by exploiting the fermentative ability of mushrooms. Do any of them whet your appetite? Before undertaking the development of these foods, we suffered countless failures and setbacks over the course of a very time-consuming process, but the joy we felt when we finally accomplished our goals made it all worthwhile. In our speed-obsessed world today, we demand immediate answers, and may tend to overlook those small realizations or little moments when we feel something is amiss. However, I hope that people continue to think for themselves without failing to catch those tiny clues that pop into their mind. I hope that our experience of being guided by mushrooms, holding as they do unknown possibilities, will encourage those who are looking for new values and ways of thinking.

Alcoholic Beverages

We tried to make wine, beer, and sake using mushrooms instead of yeast, which is usually responsible
for alcoholic fermentation. In sake brewing, rice starch saccharification by koji mold and alcoholic
fermentation by yeast occur simultaneously, and mushrooms here played the role of these two starter
cultures for both processes. In terms of the alcohol concentration, the wine produced with oyster mushrooms had the highest at 12.2 percent, while beer made with matsutake had 4.6 percent, and sake made with enoki had 3 percent. The red wine made with oyster mushrooms had a delicious taste that reminded me of the traditional wines I tasted in Tuscany, Italy, during my time studying in Germany. The sake brewed with matsutake had a particularly fragrant aroma.
We had the opportunity to compare ours with the producer of another matsutake sake, which is made by steeping the mushrooms, and found that our sake held its own in terms of taste and aroma.

Cheese
Mushrooms were used as substitutes for lactic acid bacteria, the starter culture that initiates fermentation, and rennet, a type of enzyme that coagulates milk during the cheesemaking process. In concrete terms, we succeeded in producing a fresh cheese by adding mushroom mycelia to milk and fermenting it. Imagine the appearance and taste of mushroom flavored cottage cheese. When we published our findings in a paper, an Irish cheese research institute fiercely complained that something fermented with mushrooms cannot be called cheese. They understood when we explained that we use the English descriptor “cheese-like,” but needless to say, the intensity of the response gave us a scare.

Fermented Soybeans
Natto is a fermented soybean food made by cultivating a variety of Bacillus subtilis on steamed soybeans. The bacteria produce various enzymes, including protease, which breaks down soybean protein, making ordinarily difficult-to-digest soybeans very digestible.
We tried to produce fermented soybeans using mushrooms, which have notably high protease activity.
The results had an appearance similar to tempeh, a fermented soybean food from Indonesia, and a unique flavor. Furthermore, our findings indicated that the food lasts a long time, withstanding storage at room temperature for over a year and a half, and continuing to maintain the antithrombin and fibrinolytic activity from the mushrooms or generated during the fermentation process.

Miso
Miso is made by steaming rice, which is then inoculated with spores of Aspergillus oryzae. The rice is incubated to allow the mold to grow, creating koji rice. Steamed soybeans are added to the koji rice and the mixture is fermented. This process involves four enzymes: amylase, protease, lactate dehydrogenase, and alcohol dehydrogenase. We searched for eryngi and other mushrooms that contain these four enzymes and attempted to make miso. The resulting miso had a distinctive flavor and also contained new physiologically active substances with the antithrombin and fibrinolytic activity mentioned above.

Fermented Plums
Umeboshi is a type of pickled plum preserved by salting without fermentation. Recently, reduced-salt
umeboshi has been produced, though this has the disadvantage of a reduced shelf life. We succeeded
in improving the shelf life by fermenting the plums with mushrooms and using no salt, and in adding the three aforementioned substances that contribute to preventing blood clots.