The Kumamoto Prefecture Sake Institute serves two purposes: first, to maintain and manage Kumamoto Yeast, the stock for Kyokai #9 Yeast; and second, to make Koro-brand sake.

The Kumamoto Prefecture Sake Institute was founded in 1909 at the request of brewers within the prefecture in order to improve the quality of local sake. At that time, the makers of akazake, the classical standard tipple for locals, were thinking about converting to sake brewing, and local brewers wanted to improve the techniques in use at the time in Kumamoto. The founding chief engineer, Nojiro Kinichi, developed innovations such as the Nojiro Ceiling Aperture, Bag Suspension, and the Double Vat Method, while also providing guidance for local brewers. In 1952, Nojiro was able to isolate what was to become Kumamoto Yeast. It was later distributed by the Brewing Society of Japan as Kyoukai #9 Yeast, and is now being used by brewers throughout Japan.

Satoshi Morikawa, production director and chief brewer, understands the history of the Institute: “Our role as both a research organization and as a brewery is a rare combination in Japan. Because we brew ourselves, we have accumulated a lot of data that we’re able to share.”

To gather more data on yeast, production is started on four batches of sake per week. Tanks from batches differing in season of production, rice variety, rice polishing level, etc., are kept together so they can be easily compared. The research-focused nature of the Institute is reflected in the emphasis on keeping things simple in production, from rice steaming to koji making.
Morikawa states, “Accidents aren’t what tastes best; it’s when you brew what you’re aiming for.” With this approach, the daiginjo version of Koro, the Institute’s brand of sake, is a famously rare sake that has fans all over Japan.