Still learning.Still becoming.
In the 2025 brewing year, we stopped using Kyokai yeast, supplied by the Brewing Society of Japan. We are rethinking our craft in the brewery we have inherited. For us, this is a second beginning.
We are still working toward the sake we want to make. Here is what we do now, and what we hope comes next.
Every glass begins
with a small fermentation.
Yeast produces the alcohol in sake. The shubo, or fermentation starter, is a small batch prepared to help that yeast develop and work well.
We use kimoto, in which lactic acid bacteria from the brewery acidify the starter. Cultured yeast is added only to the first starter. From the second starter onward, we add no cultured yeast.
Looking to the brewery’s environment and its microorganisms for the beginnings of fermentation: this is what we mean by Ambient Fermentation.
Shubo, received.
Moromi, nurtured.
Even as our methods change, these two responsibilities remain.
Receive
Prepare an environment in which microorganisms can thrive. Receive the potential for fermentation that this brewery offers.
Nurture
Bring our craft to that fermentation. Work with its character to shape a beautiful, elegant sake.
Make room for
a healthy beginning.
Prepare the rice and koji, rice cultivated with koji mould. Ready the tools. Attend to temperature and hygiene. Read the fermentation through its aromas, bubbles and measurements.
Receiving takes work. We prepare the conditions in which microorganisms can thrive and support the starter as fermentation gets underway.
Cultured yeast is added
only to the first starter.
Return yeast from our brewery
We culture yeast isolated from our own shubo and add it to the first starter.
No cultured yeast added
We do not add cultured yeast to each new starter. We prepare the brewery environment and support the start of fermentation.
We do not add lactic acid bacteria. We do not use Kyokai yeast.
Our aim is for even the first starter to begin without adding cultured yeast. We want to nurture the conditions in which the brewery’s lactic acid bacteria and yeast can work, and carry that life forward.
Bring its character
into a beautiful glass.
We add rice, koji and water to the shubo to build the moromi, or main mash. From here, we nurture the fermentation toward the taste we hope to achieve.
- ReadAssess the day’s condition through aroma, foam, taste and analysis.
- AdjustRespond to the progress of fermentation by adjusting temperature and other conditions, seeking a balance of acidity and umami.
- FinishFrom pressing through pasteurisation and storage, consider how the sake will feel in the glass.
We read the differences between years and batches, and take responsibility for the sake that reaches you. That is what nurturing means to us.
Keep the depth.
Lighten the weight.
Layers of acidity and umami are an essential part of Ryusei’s character. We want to keep that depth while making the sake feel lighter and easier to enjoy.
Bringing different batches consistently toward our intended taste is still a challenge. As we learn to work with yeast isolated from our brewery, we have explored many ways of adjusting our brewing.
Working with acidity.
We have adjusted temperatures during odori, the rest day in the staged build-up of the mash, and during moromi fermentation to explore acidity and flavour balance.
Attention to the details.
We have reviewed glove use and changes of clothing during koji making, looking again at the working environment that supports fermentation.
Seeking harmony.
We have explored balance by finishing sake as genshu, without diluting it with water. We have also investigated ways to cool it rapidly after pasteurisation using our existing equipment.
We do not see today’s Ryusei as a finished form.
We hope you will enjoy discovering how it changes, one glass at a time.
Four ways to look
deeper into our brewing.
Start with whichever question interests you.
How do kimoto and sokujo differ?
Both create an acidic environment in which yeast can work well. Kimoto relies on lactic acid produced by lactic acid bacteria. In sokujo, brewers add lactic acid prepared for brewing.
Some breweries also add cultured lactic acid bacteria when making kimoto. Even within kimoto brewing, where those bacteria come from is a choice each brewery makes.
At Fujii Shuzo, every sake is brewed using kimoto, and we do not add lactic acid bacteria. We prepare conditions for bacteria in the brewery environment to grow and acidify the starter. We value nurturing the beginnings of fermentation here and carrying that capacity forward.
Where the yeast comes from is a separate choice. Kimoto can also be made with Kyokai yeast. At Fujii Shuzo, cultured yeast is added only to the first starter; from the second starter onward, we add no cultured yeast.
Further reading: Lactic acid bacteria in kimoto-type starters — Hiroshima Prefecture (in Japanese) ↗
What do you manage in Ambient Fermentation?
We watch temperature, humidity, hygiene, tools, working conditions and microbial activity. By “microbial community,” we mean not just lactic acid bacteria and yeast, but the microorganisms present and their relationships with one another.
Our focus shifts from specifying every organism to preparing the environment and supporting its activity. Daily observation and adjustment remain essential. We take responsibility for safety and quality throughout the brewing process.
What do “agricultural” and “cultural” brewing mean to you?
A farmer reads the soil and seasons, then prepares the conditions for growth. In a similar way, we cultivate the relationship between the brewery environment and fermentation. This is the sense in which we call our approach “agricultural.”
We also distinguish between nurturing the capacity to begin fermentation within the brewery and carrying it into subsequent brews, and assembling that capacity from externally supplied yeast, lactic acid and other inputs. We describe the first as rooted in local culture and the second as supported by the wider systems of modern production.
These are ways of thinking about our own brewing, not a ranking of other breweries or methods.
Do you add yeast to every starter?
We add yeast isolated and cultured from our own shubo only to the first starter. From the second starter onward, we add no cultured yeast.
Our goal is for the first starter, too, to begin without adding cultured yeast. To work toward that, we nurture an environment in which the brewery’s microorganisms can thrive.
Meet the brewery in a glass of Ryusei.
Try it with food, and at different temperatures.
Discover how its acidity, umami and finish unfold.
