Researchers discovered that fermented rice made with a special mold called Aspergillus oryzae contains an enzyme that helps a beneficial gut bacteria called Faecalibacterium prausnitzii grow better. This bacteria is important for digestive health. When scientists added fermented rice extract to lab cultures of this bacteria, it grew stronger and produced more of a helpful substance called butyrate. The key ingredient appears to be an enzyme called alpha-amylase that breaks down starch, giving the bacteria the nutrients it needs to thrive. This finding suggests that eating fermented rice foods might naturally support the growth of good bacteria in your digestive system.

The Quick Take

  • What they studied: Whether fermented rice can help a specific type of beneficial gut bacteria grow better in laboratory conditions
  • Who participated: This was a laboratory study using bacterial cultures, not human volunteers. Scientists tested how a beneficial gut bacteria responded to fermented rice extract in controlled conditions
  • Key finding: Fermented rice extract made with Aspergillus oryzae mold increased the growth of Faecalibacterium prausnitzii bacteria by about 1% concentration in lab cultures, and the bacteria produced more butyrate, a substance that supports gut health
  • What it means for you: Eating fermented rice foods may help support the growth of beneficial gut bacteria naturally. However, this was a lab study, so we need human studies to confirm these benefits actually happen when people eat fermented rice

The Research Details

Scientists started with regular steamed rice and fermented it using a mold called Aspergillus oryzae, which is commonly used in Asian cooking to make foods like miso and sake. They then extracted the liquid part of the fermented rice and tested it on a beneficial gut bacteria called Faecalibacterium prausnitzii in laboratory dishes. They compared how well the bacteria grew with the fermented rice extract versus without it. To figure out what ingredient was responsible for the growth boost, they separated the extract into different parts using a special technique and tested each part. They also used advanced technology called mass spectrometry to identify exactly which molecules were helping the bacteria grow. Finally, they tested whether adding the specific enzyme (alpha-amylase) and starch together would have the same effect.

This research approach is important because it helps identify the exact ingredients in fermented foods that might be beneficial for our health. By studying bacteria in controlled lab conditions first, scientists can understand the mechanism before testing in humans. This saves time and money on human studies and helps us understand why fermented foods have been valued in traditional diets for thousands of years.

This is a well-designed laboratory study published in a reputable scientific journal. The researchers used multiple methods to identify the active ingredient, which strengthens their findings. However, this is a laboratory study using bacteria in dishes, not human subjects, so the results need to be confirmed in human studies before we can be certain these benefits occur when people eat fermented rice

What the Results Show

When scientists added fermented rice extract to the lab cultures, the beneficial bacteria Faecalibacterium prausnitzii grew significantly better compared to cultures without the extract. The bacteria also produced more butyrate, which is a short-chain fatty acid that helps protect the gut lining and supports overall digestive health. Through their analysis, researchers identified that the main active ingredient was an enzyme called alpha-amylase that comes from the Aspergillus oryzae mold. When they added this purified enzyme along with starch to the bacterial cultures, it had the same growth-promoting effect as the whole fermented rice extract. This suggests the enzyme works by breaking down starch into simpler sugars that the bacteria can easily use for energy and growth.

The research showed that the fermented rice extract worked better than unfermented rice, indicating that the fermentation process creates something special. The enzyme appears to work by making starch more digestible for the bacteria, essentially pre-processing the food so the bacteria can absorb it more efficiently. The increased butyrate production is particularly important because this substance has been linked to reduced inflammation, better immune function, and improved digestive health in previous research.

This research builds on existing knowledge that fermented foods support gut health. Previous studies have shown that Faecalibacterium prausnitzii is one of the most important beneficial bacteria in a healthy gut, and low levels are associated with digestive problems. This study adds to that knowledge by identifying a specific mechanism: fermented rice provides enzymes that help this bacteria thrive. The findings align with traditional use of fermented rice in Asian cuisines and support the growing scientific evidence that fermented foods offer real health benefits.

This study was conducted entirely in laboratory dishes with bacteria cultures, not in human bodies. The human gut is much more complex with hundreds of different bacteria competing for nutrients, so results may differ in real life. The study doesn’t tell us how much fermented rice a person would need to eat to see these benefits, or whether the enzyme survives digestion when eaten. Additionally, the study didn’t test whether other fermented foods might have similar effects. More research in humans is needed to confirm these laboratory findings translate to real health benefits

The Bottom Line

Based on this research, eating fermented rice foods like koji or fermented rice products may support beneficial gut bacteria growth. However, this is preliminary laboratory evidence. A reasonable approach would be to include fermented rice foods as part of a balanced diet rich in fiber and diverse foods. This is a low-risk addition that aligns with traditional dietary practices. Confidence level: Low to Moderate (laboratory evidence only, human studies needed)

Anyone interested in supporting gut health through diet may find this relevant. People with digestive issues, those taking antibiotics, or anyone wanting to optimize their microbiome might be particularly interested. However, people with mold allergies or sensitivities should be cautious with fermented foods. This research is not a treatment for any disease and shouldn’t replace medical advice for digestive disorders

If fermented rice does support beneficial bacteria growth in humans, you would likely need to eat it regularly for several weeks to see changes in your gut bacteria composition. Benefits to digestive health or overall wellness could take 4-8 weeks of consistent consumption to become noticeable, though this timeline is based on general microbiome research, not this specific study

Want to Apply This Research?

  • Track daily consumption of fermented rice products (servings per day) and note any changes in digestive comfort, energy levels, or bowel regularity over 6-8 weeks
  • Add one serving of fermented rice food (such as koji, amazake, or fermented rice products) to your daily diet and track consistency. Start with small amounts if new to fermented foods to allow your digestive system to adjust
  • Create a weekly log noting: fermented rice intake, digestive symptoms (bloating, regularity, comfort), energy levels, and overall wellness. Compare baseline (week 1) to weeks 4-8 to identify any patterns or improvements

This research is a laboratory study and has not been tested in humans. The findings suggest potential benefits but do not constitute medical advice or treatment recommendations. Fermented rice should not be used as a substitute for medical treatment of any digestive condition. People with mold allergies, compromised immune systems, or those taking certain medications should consult a healthcare provider before significantly increasing fermented food consumption. Always speak with a doctor or registered dietitian before making major dietary changes, especially if you have existing health conditions