Rice-based fermented products: the functional properties of the microorganisms in the defined starter contributing to melanogenesis inhibition activity.

Rice contains numerous nutrients and biologically active compounds. The phytochemical composition of rice varies among cultivars, leading to diversities in biological activities. Fermentation is an efficient way of improving nutrient bioavailability and the functional properties of raw materials. It enhances and/or synthesizes the compounds with health-promoting or decreased antinutritive compounds during the fermentation process. Rice-based fermented products have been reported for enhancing various biological activities, including antioxidant, anti-cancer, anti-diabetes, anti-wrinkle and anti-melanogenesis activities. Melanogenesis, melanin biosynthesis, is the cause of human skin pigmentation; however, the accumulation of melanin leads to skin hyper-pigmentary disorders, such as freckles and melasma. In this review, the information on rice-based fermented products has been assembled to illustrate the fermented rice properties, especially melanogenesis inhibition activity, including functional roles of the microorganisms in the fermented rice products.

Metatranscriptomics Reveals Sequential Expression of Genes Involved in the Production of Melanogenesis Inhibitors by the Defined Microbial Species in Fermented Unpolished Black Rice.

Fermented products require metabolic enzymes from the microbial community for desired final products. Using a metatranscriptomic approach, the role of microorganisms in fermented products on producing compounds with a melanogenesis inhibition activity has not yet been reported. Previously, unpolished black rice (UBR) fermented with the E11 starter containing Saccharomyces cerevisiae, Saccharomycopsis fibuligera, Rhizopus oryzae, and Pediococcus pentosaceus (FUBR) showed potent melanogenesis inhibition activity. This study aimed to investigate the function of these defined microbial species in producing melanogenesis inhibitors in the FUBR using a metatranscriptomic approach. The melanogenesis inhibition activity increased in a fermentation time-dependent manner. Genes related to melanogenesis inhibitors synthesis such as carbohydrate metabolism, amino acids synthesis, fatty acids/unsaturated fatty acids synthesis, and carbohydrate transporters were analyzed. Most genes from R. oryzae and P. pentosaceus were upregulated in the early stage of the fermentation process, while those of S. cerevisiae and S. fibuligera were upregulated in the late stage. FUBR production using different combinations of the four microbial species shows that all species were required to produce the highest activity. The FUBR containing at least R. oryzae and/or P. pentosaceus exhibited a certain level of activity. These findings were in agreement with the metatranscriptomic results. Overall, the results suggested that all four species sequentially and/or coordinately synthesized metabolites during the fermentation that led to a FUBR with maximum melanogenesis inhibition activity. This study not only sheds light on crucial functions of certain microbial community on producing the melanogenesis inhibitors, but also paves the way to initiate quality improvement of melanogenesis inhibition activity in the FUBR. IMPORTANCE Fermentation of food is a metabolic process through the action of enzymes from certain microorganisms. Although roles of the microbial community in the fermented food were investigated using metatranscriptomic approach in terms of flavors, but no study has been reported so far on the function of the microorganisms on producing compounds with a melanogenesis inhibition activity. Therefore, this study explained the roles of the defined microorganisms from the selected starter in the fermented unpolished black rice (FUBR) that can produce melanogenesis inhibitor(s) using metatranscriptomic analysis. Genes from different species were upregulated at different fermentation time. All four microbial species in the FUBR sequentially and/or coordinately synthesized metabolites during fermentation that led to a FUBR with maximal melanogenesis inhibition activity. This finding contributes to a deeper understanding of the roles of certain microbial community during fermentation and led to the knowledge-based improvement for the fermented rice with potent melanogenesis inhibition activity.

Metaproteomic investigation of functional insight into special defined microbial starter on production of fermented rice with melanogenesis inhibition activity.

Fermentation of rice grains requires diverse metabolic enzymes to be synchronously synthesized by the microbial community. Although many studies have used a metaproteomic approach to investigate the roles of microorganisms in improving the flavor of fermented foods, their roles in producing compounds with biological activity have not yet been reported. In a previous study the ferment obtained from unpolished black rice (UBR) fermented with a defined microbial starter (De-E11), comprised of Rhizopus oryzae, Saccharomycopsis fibuligera, Saccharomyces cerevisiae, and Pediococcus pentosaceus, (fermented UBR; FUBR) showed a strong melanogenesis inhibition activity in B16F10 melanoma cells. Hence, in this study, the roles of these microorganisms in producing the melanogenesis inhibitor(s) in FUBR was investigated using a metaproteomic approach. The melanogenesis inhibition activity of the FUBR liquid (FR-Liq) was found to increase with longer fermentation times. R. oryzae and S. cerevisiae were the major hosts of proteins related to the biosynthesis of melanogenesis inhibitor(s) in the FUBR. During fermentation, the enzymes involved in the degradation of UBR and in the carbohydrate metabolic process were identified. These enzymes were associated with the process of releasing of bioactive compound(s) from UBR and the synthesis of organic acids from the microorganisms, respectively. In addition, enzymes involved in the synthesis of some known melanogenesis inhibitor(s) and in the degradation of the melanogenesis stimulator (arsenate) were detected. Varying the combination of microorganisms in the De-E11 starter to produce the FR-Liq revealed that all four microorganisms were required to produce the most potent melanogenesis inhibition activity. Taken together with the metaproteomics results, this suggested that the microorganisms in De-E11 synchronously synthesize the FR-Liq with melanogenesis inhibition activity. In conclusion, this information on the metaproteome in FUBR will increase our understanding of the microbial metabolic modes and could lead to knowledge-based improvements in the fermented rice process to produce melanogenesis inhibitor(s).

Fermented Unpolished Black Rice (Oryza sativa L.) Inhibits Melanogenesis via ERK, p38, and AKT Phosphorylation in B16F10 Melanoma Cells.

Melanin is a major factor that darkens skin color as one of the defense systems to prevent the harmful effects of UV light. However, darkened skin from the localized or systemic accumulation of melanin is viewed in many cultures as an esthetic problem. Consequentially, searching for antimelanogenic agents from natural sources is very popular worldwide. Previous screening of fermented rice products, obtained from various rice cultivars fermented with different sources of loog-pang (Thai traditional fermentation starter), revealed that the highest ability to reduce the melanin content in B16F10 melanoma cells was from unpolished black rice fermented with a defined starter mixture of microbes isolated from loog-pang E11. The aim of this study was to investigate the mechanism of the fermented unpolished black rice (FUBR) on the inhibition of melanogenesis in B16F10 melanoma cells. The strongest reduction of cellular melanin content was found in the FUBR sap (FUBRS). The melanin reduction activity was consistent with the significant decrease in the intracellular tyrosinase activity. The FUBRS showed no cytotoxic effect to B16F10 melanoma or Hs68 human fibroblast cell lines. It also significantly reduced the transcript and protein expression levels of tyrosinase, tyrosinase-related protein 1 (TYRP-1), TYRP-2, and microphthalmia-associated transcription factor. Furthermore, it induced a significantly increased level of phosphorylated ERK, p38 and Akt signaling pathways, which likely contributed to the negative regulation of melanogenesis. From these results, a model for the mechanism of FUBRS on melanogenesis inhibition was proposed. Moreover, these results strongly suggested that FUBRS possesses antimelanogenesis activity with high potential for cosmeceutical application as a skin depigmenting agent.