Rice Ferment in Japanese Cosmetics: Science and Benefits of the Bizen Ritual

Origin, high skin efficacy, and artisanal, sustainable production. All that makes our organic rice ferment the living heart of Bizen skincare.

What is Bizen rice starter?
Le koji et les levures à l'œuvre : la fermentation artisanale du riz Bizen.

Rice transformation through koji fermentation

Bizen rice ferment is obtained through an ancestral fermentation process under the action of koji (Aspergillus oryzae), a noble fungus stemming from Japanese culinary and artisanal traditions.

During this natural transformation, this microorganism breaks down:

  • Starch into hydrating simple sugars.
  • Proteins into essential amino acids.
  • Lipids into protective fatty acids.

Added natural yeasts consume these simple sugars to produce alcohol. Once the alcohol is separated from the mixture, we collect the precious residue of this process: fermented rice lees. It is this concentrate of exceptional active ingredients that constitutes the signature ingredient of Maison Bizen.
Les ingrédients naturels de la fabrication du ferment de riz Bizen : riz complet biologique et koji.

A Living Formula: Organic Whole Rice, Koji, and Yeast

To produce our ferment, we exclusively use organic whole rice. By preserving its natural outer layers—the germ and the bran—the entire grain retains its original wealth of nutrients: fiber, B vitamins, antioxidant minerals, and moisturizing agents.

This organic fermented rice lees is integrated into the heart of our cosmetic formulations in two forms:

  • As a concentrated extract in our lotion, balm, and moisturizing cream.
  • As a pure paste in our handcrafted soap.
Louche traditionnelle puisant la lie de riz ferment pour les soins Bizen

A concentrate of natural active ingredients: fermented rice lees

Bizen fermented rice lees, a true reservoir of amino acids, vitamins and minerals essential for maintaining skin hydration.

The Scientific Benefits of Bizen Rice Ferment for Skin


Efficacy measured and tested by an independent laboratory

Deep Hydration & Water Retention


Rich in 16 free amino acids, essential components of NMF (Natural Moisturizing Factors), maintains a supple and hydrated skin barrier.

Hyaluronic Acid


Inhibits the natural fragmentation of hyaluronic acid to preserve the skin's water reserves.

Antioxidant & Anti-aging


Neutralizes free radicals, fights oxidative stress, and preserves skin firmness against skin aging.

Benefits and biological properties validated by independent efficacy tests. Fermentation Data.

Certifications & INCI

Brown rice

Certified organic JAS (Japanese Agricultural Standards).

Fermented Rice Lees

Certified Ecocert Cosmos and USDA Organic.

Official INCI designation

Aspergillus/Saccharomyces Rice Ferment Lees.
La preuve scientifique : une hausse significative et continue de la teneur en eau de la couche cornée sur 2 mois d'application quotidienne d'extrait de ferment de riz Bizen.

Scientific Proof: Clinically Measured Hydration

To assess the efficacy of our active ingredient, a comparative study measured the water content of the stratum corneum in a control group (without the active ingredient) versus a group applying the Bizen rice ferment extract.

Study Results:

  • After 1 month: The Bizen group's hydration curve begins a steady increase.
  • At 2 months: Skin hydration significantly increases compared to the control group.
  • Conclusion: Rice ferment provides progressive, deep, and lasting improvement in hydration with daily use.
Un concentré d'actifs naturels : la lie de riz fermenté, véritable réservoir d'acides aminés, de vitamines et de minéraux essentiels au maintien de l'hydratation de la peau.

The Origins of Japanese Cosmetics:

The Tradition of Rice and Sake Brewers

The first Japanese cosmetics were born in the kitchen, made by women, from rice and other nutritional treasures.

Rice rinsing water, naturally loaded with starch, was used to soften the complexion and brighten the hair.

Rice bran, a husk rich in minerals and fibers, was placed in small cloth bags to gently cleanse and exfoliate the skin.

The secret of sake brewers' hands

The connection with fermentation comes from an observation: sake brewers, who handle rice ferments with their bare hands daily, had surprisingly young and smooth hands.

Observing this vitality, Japanese women incorporated sake lees (Sake kasu) into their rituals in the form of regenerating face masks — a centuries-old tradition whose science Bizen perpetuates today.
Lina, fondatrice de Fermenstation, dans les rizières d'Iwate où commence la transformation de notre ingrédient signature.

An exceptional rice ferment: Certified organic, made in Japan, and part of the circular economy

It all begins in the Iwate region, in northern Japan. It's in the heart of these rice paddies that Lina Watanabe Sakai, CEO of Fermenstation, revitalized fallow land and created a circular ecosystem where the valorized residues from rice fermentation are transformed into natural cosmetic active ingredients with high biotechnological value.

The whole rice we cultivate is:

  • Certified organic and grown without chemical inputs.
  • Sourced through a short, eco-responsible supply chain, respecting the rhythm of the seasons, the soil, and the people.
L'art japonais du Kintsugi : célébrer les empreintes du temps et sublimer ce qui croît avec les années, au cœur de notre philosophie du bien vieillir.

Fermentation and the Vision of Beauty: The Art of Aging Well

Fermentation opens up a temporality that escapes both the linearity of our bodies and the cyclical nature of the seasons. It is not an alteration: that which ferments enriches itself, improves, gains in depth and complexity.

Just as the fermentation of rice by koji gives rise to umami — the fifth flavor of taste — in cosmetics, it releases precious amino acids that protect, regenerate, and nourish the skin.

Aging well means adopting this same philosophy: viewing time not as a loss, but as a progressive revelation of one's deep beauty. To endure but above all to become. To let grow. To accompany the skin without forcing it.