What Was Produced by Fermentation? From Elucidation of Ingredients to Verification of Effects on Skin

<p>We have developed a fermentation liquid based on germinated brown rice, which has a high nutritional value, using the yeast Lachancea thermotolerans. The fermented liquid is known to be beneficial to the skin and to contain amino acids, but little is known about its other components. Metabolomics is the study of small molecules and has been used in the pharmaceutical and food industries to identify metabolic changes. We used a metabolomics approach to comprehensively analyze the fermentation liquid, determine the components of the fermentation, and correlate them with functionality for the skin. Acetylpolyamines were identified as a characteristic metabolite of the fermentation liquid. An in vitro evaluation of the efficacy of polyamines and their derivatives, acetylpolyamines, confirmed that they promoted hyaluronic acid production in the epidermis and dermis, inhibited melanin production, and promoted glutathione production. Next, the permeability of acetylpolyamines and polyamines was evaluated using a three-dimensional human epidermis experimental model. Polyamines and acetylpolyamines penetrated to the lower part of the cornified layer in 1 h, whereas the permeability of the granular layer differed among acetylpolyamines. Using a three-dimensional human epidermis model, hyaluronic acid production around the basement membrane induced by permeating spermidine trihydrochloride and N⁸-Acetylspermidine dihydrochloride was confirmed. Using a metabolomics approach, we have contributed to a better understanding of the active compounds present in fermented liquids that can be used for skin wellness.</p>