Sake Microbes Overrun Factory
July 27, 2014

Sake Microbes Overrun Factory

It could be the plot of a highly scientific disaster movie, if their main threat wasn’t making sake taste nice. It has been discovered that the microbes that help to create sake, the Japanese alcohol made from rice, are not only in the product doing their job, but everywhere and on all kinds of surfaces in the factory. It may be the start of a microbe revolution slash prison break, or more likely, we have just not studied this phenomenon much before.

The American Society for Microbiology explains that this is the first time such a census of the microbial population of a sake brewer has been taken. Research published ahead of print in the journal Applied and Environmental Microbiology found that “microbial populations found on surfaces in the facility resemble those found in the product, creating the final flavor.”

The corresponding author of the research, David A. Mills of the University of California, tells us that many sake makers inoculate with a combination of bacteria and yeast, but that his team investigated a sake brewery where inoculation is limited to a single species, Aspergillus oryzae. Despite this initial single inoculation, microbial populations change considerably at each fermentation stage, known in Japanese as koji, moto, and moromi.

“The kojii fermentation is dominated by an inoculated fungus, Aspergillus oryzae, which helps process the rice into smaller, more available sugars,” said Mills. “The Kojii is then diluted with steamed rice and water to form the seed mash or moto. In this stage the alcoholic fermentation commences with yeast and various lactic acid-producing bacteria populations expanding.” Next, major fermentation takes places as “Yeast perform the alcoholic fermentation, while a range of other bacteria—Bacillus, Staphylococcus, Lactobacillus—consume available nutrients and stabilize the product.”

Throughout the entire process, “most of these organisms—with the exception of the added A. oryzae—could also be found on the equipment surfaces, suggesting the house microbiome provides the necessary microbes to carry out the fermentation.” We can conclude, then, “The environmental conditions are important for controlling these fermentations.”

The project set out with the intention to answer the question of whether the general environment, surfaces of equipment and the like, within the factory have microbiota that are similar to those that are added to ferment the product. The answer was conclusive, the environment is one big sake making world, colonized by the the things that also contribute to the direct process of making liquid to get us drunk  – and share good times, and continue ancient traditions, of course. The find only adds to the prestige of ancient alcohol such as this, in my opinion, knowing that the whole location that it comes from is a huge, living entity that contributes to the final enjoyment.

Although the concept of monitoring entire facilities in this way is at an early stage, the team has done similar studies on the working environments of an artisanal cheese maker and a wine producer. They had similar results as those from the sake factory, and Mills expects that such monitoring will become the norm in future, contributing to better products in respect to both enjoyment and health & safety.

Image Credit: Thinkstock

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John is a freelance writer from the UK, currently living in Japan and thoroughly enjoying their food and whiskey. His first novel, Three Little Boys, and his travel book, Following Football, are currently available on

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