Sangkaew Orrarat, Kaenboot Suttida, Nhujak Thumnoon, Kulsing Chadin, Tungkijanansin Nuttanee, Roytrakul Sittiruk, Yompakdee Chulee
Department of Microbiology, Faculty of Science, Chulalongkorn University, Bangkok, Thailand.
Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok, Thailand.
PeerJ. 2025 Jun 4;13:e19533. doi: 10.7717/peerj.19533. eCollection 2025.
Fermentation of rice can enhance the release of bioactive ingredients and generate diverse microbial metabolites contributing to various functional properties. Previous studies have demonstrated that the mixture of selected microorganisms called "De-E11 starter," comprised of , , and yields fermented unpolished black rice sap (FUBRS) with a melanogenesis inhibition activity. To further understand this fermentation process, we characterized FUBRS and profiled its metabolite composition in comparison to unfermented unpolished black rice (Un-FR), recognizing the substantial enzymatic activity of FUBRS microorganisms and their potential for extensive metabolite production. The results indicated that fermentation decreased the pH, increased total acid content and elevated reducing sugar content. Moreover, significant alterations in phytochemical profiles were observed in FUBRS. In terms of biological activity, fermentation significantly enhanced antioxidant and tyrosinase/melanogenesis inhibitory activities. Untargeted metabolomic analysis utilizing orthogonal projections to latent structures discriminant analysis (OPLS-DA) revealed a clear differentiation in metabolite profiles between FUBRS and Un-FR. Volcano plot analysis (≥2-fold change) indicated a general increase in metabolites, including sugars, phenolic acids, organic acids, and fatty acids, after fermentation. Quantitative analysis confirmed the accumulation of -hydroxybenzoic acid, lactic acid, acetic acid, and succinic acid, that are all known melanogenesis inhibitors. This study provides valuable insights into the characteristics and metabolite profile of FUBRS, and informing strategies for optimizing the fermentation processes to enhance the production of melanogenesis and tyrosinase inhibitory compounds, and identifying key metabolites as critical biomarkers for monitoring and controlling these processes. Together, they will facilitate the efficient and reproducible generation of high-efficacy ingredients for the cosmetic, nutraceutical, and potentially pharmaceutical industries.
大米发酵可增强生物活性成分的释放，并产生多种具有不同功能特性的微生物代谢产物。先前的研究表明，由[具体微生物名称1]、[具体微生物名称2]、[具体微生物名称3]和[具体微生物名称4]组成的名为“De-E11发酵剂”的特定微生物混合物，可产生具有黑素生成抑制活性的发酵糙黑米糊（FUBRS）。为了进一步了解这一发酵过程，我们对FUBRS进行了表征，并与未发酵的糙黑米（Un-FR）相比分析了其代谢产物组成，认识到FUBRS微生物具有显著的酶活性及其产生大量代谢产物的潜力。结果表明，发酵降低了pH值，增加了总酸含量并提高了还原糖含量。此外，在FUBRS中观察到植物化学特征的显著变化。在生物活性方面，发酵显著增强了抗氧化和酪氨酸酶/黑素生成抑制活性。利用正交投影到潜在结构判别分析（OPLS-DA）的非靶向代谢组学分析显示，FUBRS和Un-FR之间的代谢产物谱有明显差异。火山图分析（≥2倍变化）表明，发酵后包括糖类、酚酸、有机酸和脂肪酸在内的代谢产物普遍增加。定量分析证实了对羟基苯甲酸、乳酸、乙酸和琥珀酸的积累，这些都是已知的黑素生成抑制剂。本研究为FUBRS的特性和代谢产物谱提供了有价值的见解，并为优化发酵过程以提高黑素生成和酪氨酸酶抑制化合物的产量提供了策略，并确定关键代谢产物作为监测和控制这些过程的关键生物标志物。它们共同将有助于为化妆品、营养保健品和潜在的制药行业高效且可重复地生产高效成分。
