【AuB Paper Announcement】Mechanism for Increasing Good Gut Bacteria by Rice Koji Elucidated – α-Amylase is Key to Proliferation
AuB and Kagawa University have elucidated how rice koji increases the beneficial gut bacterium *Faecalibacterium prausnitzii*. The enzyme α-amylase in rice koji produces oligosaccharides that feed and promote the growth of this bacterium, scientifically validating a traditional belief.
📋 Article Processing Timeline
- 📰 Published: April 8, 2026 at 19:10
- 🔍 Collected: April 8, 2026 at 10:30
- 🤖 AI Analyzed: April 20, 2026 at 17:19 (294h 48m after Collected)
AuB (AuB Inc.), a gut microbiome research company represented by former Japan national football player Keita Suzuki, has elucidated the mechanism by which rice koji increases butyrate bacteria (beneficial bacteria) residing in the gut, through joint research with Kagawa University.
This study focused on 'Faecalibacterium prausnitzii'※1 (hereinafter referred to as 'F. prausnitzii'), a type of butyrate bacteria that accounts for a high proportion of the gut microbiome and is currently receiving attention.
As a result, it was confirmed that F. prausnitzii proliferates using oligosaccharides generated during the process of starch decomposition by the digestive enzyme 'α-amylase' contained in rice koji.
Previously, while the saying 'Rice koji is good for the body' has been a Japanese tradition, there was no scientific explanation. This research provides results suggesting that human intake of rice koji may lead to an increase in butyrate bacteria and improvement of the gut environment.
This research was published in the international academic journal 'Scientific Reports' in January of this year (2026)※4.
※1 'Faecalibacterium prausnitzii' is a type of butyrate bacteria that controls immunity and is abundant in the intestines of healthy adults※2. While individual differences exist, it is known to account for up to 15% of gut bacteria※3.
※2 Frontiers in Microbiology (2018): [Link]
※3 BMC Genomics (2018): [Link]
※4 Scientific Reports (2026): [Link]
### 【Experiment 1】Rice Koji Extract Increases F. prausnitzii 1.2 Times More Than Distilled Water
In the research, F. prausnitzii was cultured by adding rice koji extract (an aqueous extract of rice fermented with koji mold) at concentrations of 1% and 2% to the culture medium (the base for proliferating F. prausnitzii). A control experiment was also conducted using distilled water, and the increase in F. prausnitzii was measured after 12 hours.
As a result, under conditions where rice koji extract was added, the bacteria continued to proliferate at a similar rate even after 12 hours, regardless of the extract concentration. The bacterial count in the medium increased by approximately 1.2 times compared to the condition where distilled water was added.
This study focused on 'Faecalibacterium prausnitzii'※1 (hereinafter referred to as 'F. prausnitzii'), a type of butyrate bacteria that accounts for a high proportion of the gut microbiome and is currently receiving attention.
As a result, it was confirmed that F. prausnitzii proliferates using oligosaccharides generated during the process of starch decomposition by the digestive enzyme 'α-amylase' contained in rice koji.
Previously, while the saying 'Rice koji is good for the body' has been a Japanese tradition, there was no scientific explanation. This research provides results suggesting that human intake of rice koji may lead to an increase in butyrate bacteria and improvement of the gut environment.
This research was published in the international academic journal 'Scientific Reports' in January of this year (2026)※4.
※1 'Faecalibacterium prausnitzii' is a type of butyrate bacteria that controls immunity and is abundant in the intestines of healthy adults※2. While individual differences exist, it is known to account for up to 15% of gut bacteria※3.
※2 Frontiers in Microbiology (2018): [Link]
※3 BMC Genomics (2018): [Link]
※4 Scientific Reports (2026): [Link]
### 【Experiment 1】Rice Koji Extract Increases F. prausnitzii 1.2 Times More Than Distilled Water
In the research, F. prausnitzii was cultured by adding rice koji extract (an aqueous extract of rice fermented with koji mold) at concentrations of 1% and 2% to the culture medium (the base for proliferating F. prausnitzii). A control experiment was also conducted using distilled water, and the increase in F. prausnitzii was measured after 12 hours.
As a result, under conditions where rice koji extract was added, the bacteria continued to proliferate at a similar rate even after 12 hours, regardless of the extract concentration. The bacterial count in the medium increased by approximately 1.2 times compared to the condition where distilled water was added.
FAQ
How does rice koji increase the number of beneficial bacteria in the gut?
The oligosaccharides produced by alpha-amylase in rice koji serve as food for the beneficial bacteria 'Firmicutes prausnitzii', promoting its proliferation.
Which company led this research?
AuB, a company led by former Japanese national soccer team player Keita Suzuki, conducted the research in collaboration with Kagawa University.
When and where were the results of this study published?
The results were published in the international academic journal 'Scientific Reports' in January 2026.