In this study, the microbial community present during the barley yeast fermentation of stevia leaves and its correlation with antioxidant, anti-obesity, and anti-inflammatory properties, as well as metabolites, were investigated using UPLC-Q-TOF-MS. Stevia was fermented using commercial TSB media (TSB 1, TSB 3, and TSB 5) and sucrose (Sucrose 1, Sucrose 3, and Sucrose 5) for 1, 3, and 5 days, respectively. Stevia ferments showed higher DPPH and ABTS radical scavenging capacity compared to samples incubated with sucrose for 5 days, and all six ferments inhibited nitric oxide production in a concentration-dependent manner in LPS-induced mouse macrophages. Furthermore, UPLC-QTOF-MS analysis identified 23 related substances, including 10 terpenoids (including rubusoside, steviolbioside, and rebadioside derivatives), dulcoside A, and phlomisoside II, which are indicators of stevia, as well as five flavonoids, four phenolic acids, and four fatty acids. We also identified the microbial community during fermentation via the next-generation sequencing of the 16S rRNA gene for bacteria and the internal transcribed spacer (ITS) gene for fungi. The results showed that TSB 1 and Sucrose 1 ferments were dominated by the pathogens Enterococcus hirae (58.93%) and Cronobacter sakazakii (80.92%), while samples fermented for more than 3 days were pathogen-free and dominated by lactic acid bacteria such as Pediococcus stilesii (73.37%). Microbial community analysis using the ITS region showed that Saccharomycopsis fibuligera, classified as a yeast rather than a mold, dominated the stevia fermentation regardless of the fermentation duration. In particular, the microbial community of the fermentation with a sucrose solution was dominated by S. fibuligera by more than 99% throughout the fermentation periods of 1, 3, and 5 days. Finally, to apply the stevia ferments topically to human skin, skin irritation tests were performed on 30 volunteers. The results showed that the highly concentrated extracts (1 mg/mL) of all six stevia ferments were hypoallergenic. Taken together, these findings suggest that barley nuruk fermented from stevia leaves with a sucrose solution offers promise as a natural ingredient for use in functional foods and cosmetics.

Novel microbe-derived products are gaining increasing attention for their ability to modulate skin conditions. The use of microbial metabolites to improve skin health outcomes is of particular interest because growing evidence points to the importance of natural products without side effects on human health. This study aimed to sequence the genome of Viridibacillus sp. JNUCC6 isolated from Baengnokdam, the summit crater of Mt. Halla. We further investigated the potential use of its extract as a cosmetic ingredient in controlling melanogenesis and inflammation. The genome of this strain was sequenced using both Illumina Novaseq 6000 and third-generation sequencing technology (PacBio RSII) to obtain trustworthy assembly and annotation. Different concentrations of the Viridibacillus sp. JNUCC6 extract were tested for its anti-melanogenic and anti-inflammatory effects in α-melanocyte-stimulating hormone (α-MSH)-induced B16F10 melanoma and lipopolysaccharide (LPS)-activated RAW 264.7 cells, respectively. The whole genome sequence of the strain contained 4,526,142 bp with 35.61% GC content, one contig, and 4364 protein-coding sequences. Furthermore, antiSMASH analysis of the whole genome revealed three putative biosynthetic gene clusters that are responsible for the production of various secondary metabolites. Our study found that the Viridibacillus sp. JNUCC6 extract inhibited the α-MSH-induced melanin production and tyrosinase activity in B16F10 melanoma cells. In addition, it decreased the LPS-induced nitric oxide (NO) production caused by LPS stimulation in a concentration-dependent manner. Therefore, Viridibacillus sp. JNUCC6 has potential applications as an ingredient in skin-whitening and anti-inflammatory products and can be used in the cosmetic and medical industries.

In this study, the microbial community during the barley yeast fermentation of stevia leaves and its correlation with antioxidant, antiobesity, and anti-inflammatory properties, as well as metabolites, were investigated using UPLC-Q-TOF-MS. Stevia was fermented using commercial TSB media (TSB 1, TSB 2, and TSB 3) and sucrose (Sucrose 1, Sucrose 3, and Sucrose 3) for 1, 3, and 5 days, respectively. Stevia ferments showed higher DPPH and ABTS radical scavenging capacity compared to samples incubated with sucrose for 5 days, and all six ferments inhibited nitric oxide production in a concentration-dependent manner in LPS-induced mouse macrophages. Furthermore, UPLC-QTOF-MS analysis identified 23 related substances, including 10 terpenoids, including rubusoside, steviolbioside, and rebadioside derivatives; dulcoside A; and phlomisoside II, which are indicators of stevia, as well as five flavonoids, four phenolic acids, and four fatty acids. We also identified the microbial community during fermentation via the next-generation sequencing of the 16S rRNA gene for bacteria and the internal transcribed spacer (ITS) gene for fungi. The results showed that TSB 1 and Sucrose 1 ferments were dominated by the pathogens Enterococcus hirae (58.93%) and Cronobacter sakazakii (80.92%), while samples fermented for more than 3 days were pathogen-free and dominated by lactic acid bacteria such as Pediococcus stilesii (73.37%). Microbial community analysis using the ITS region showed that Saccharomycopsis fibuligera, classified as a yeast rather than a mold, dominated the stevia fermentation regardless of the fermentation duration. In particular, the microbial community of the fermentation with a sugar solution was dominated by S. fibuligera by more than 99% throughout the fermentation periods of 1, 3, and 5 days. Finally, to apply the stevia ferments topically to human skin, skin irritation tests were performed on 30 volunteers. The results showed that the highly concentrated extracts (1 mg/mL) of all six stevia ferments were hypoallergenic. Taken together, these findings suggest that brewer's yeast fermented from stevia leaves with a sugar solution offers promise as a natural ingredient for use in functional foods and cosmetics.

Vagococcus species have been isolated from diverse environments, including aquatic, terrestrial, food-associated, and clinical sources; however, plant- and flower-associated representatives remain poorly characterized at the genomic level. In this study, we report the complete genomic sequence and analysis of Vagococcus sp. JNUCC 83, isolated from flowers of Camellia japonica collected on Jeju Island, Republic of Korea. The genome comprises a single circular chromosome of 2,472,896 bp with a GC content of 33.5 mol% and was assembled at high depth (555.43×), resulting in a high-quality complete genome. Genome-based phylogenomic analysis using the Type (Strain) Genome Server (TYGS) showed that strain JNUCC 83 forms a distinct lineage within the genus Vagococcus. Digital DNA–DNA hybridization (dDDH) values were far below the 70% species threshold, and 16S rRNA gene-based phylogeny consistently supported its independent placement, suggesting that JNUCC 83 represents a previously undescribed genomic species. Functional annotation based on EggNOG/COG analysis indicated the enrichment of genes involved in core metabolism and genome maintenance, while antiSMASH analysis identified a terpene-precursor-type biosynthetic locus encoding a polyprenyl synthase. Overall, this study expands the genomic understanding of flower-associated Vagococcus lineages and provides a foundation for future investigations into their ecological roles and potential applications as plant-derived microbial resources.

Leuconostoc suionicum strain JNUCC 76 (=CH10) was isolated from cherry blossom flowers (Prunus yedoensis) collected on Jeju Island, Republic of Korea, representing a flower-associated strain of L. suionicum. To clarify its taxonomic position and genomic characteristics, whole-genome sequencing was performed using a hybrid PacBio–Illumina approach. The complete genome was assembled into a single circular chromosome of 2.20 Mb with a GC content of 36.8% and high sequencing depth, indicating a high-quality, closed genome assembly. Genome annotation revealed a compact gene repertoire dominated by functions related to carbohydrate transport and metabolism, amino acid utilization, and core cellular processes, consistent with adaptation to plant-derived, sugar-rich environments. Genome-based phylogenomic analyses using average nucleotide identity (ANI), digital DNA–DNA hybridization (dDDH), and Genome BLAST Distance Phylogeny (GBDP) placed strain JNUCC 76 within the species L. suionicum. Genome-based metrics clearly exceeded the accepted species thresholds, supporting the assignment of the strain to L. suionicum. Secondary metabolite gene cluster analysis identified a limited number of low-complexity and precursor-oriented biosynthetic gene clusters, including RiPP-like, type III polyketide synthase, and terpene-precursor clusters, suggesting that the ecological fitness of the strain relies primarily on primary metabolism rather than extensive secondary metabolite production. Overall, this study expands current knowledge of flower-associated Leuconostoc lineages and provides a high-quality genomic framework for future comparative and functional studies. The genomic features of strain JNUCC 76 highlight floral environments as underexplored reservoirs of lactic acid bacteria diversity and support further evaluation of flower-derived Leuconostoc strains as potential postbiotic or fermentation-based resources for cosmetic and related biotechnological applications.

Bombiscardovia sp. JNUCC 75 (=CH12) was isolated from the flowers of Prunus yedoensis on Jeju Island, representing one of the few known flower-associated members of the Bombiscardovia asteroides group. Whole-genome sequencing revealed a compact 2.28 Mb genome and a functional gene profile enriched in translation, amino-acid metabolism, and DNA repair. Although the strain contains a pseudogene content comparable to other B. asteroides-group members, the overall genomic architecture—together with the presence of stress-response and polyprenyl/terpenoid biosynthetic pathways—suggests adaptation to oxygen-variable, phenolic-rich, and UV-exposed floral environments. Comparative genomic analyses (OrthoANIu 97.16%; dDDH 72.7%) demonstrated that JNUCC 75 is closely related to B. polysaccharolytica yet forms a genetically distinct lineage within the group. Genome mining uncovered two previously unreported terpenoid/polyprenyl biosynthetic gene clusters, indicating a novel isoprenoid-derived metabolic repertoire with potential roles in membrane stabilization and oxidative-stress defense. These genomic features collectively position JNUCC 75 as a bridge between gut-associated and environmental bifidobacteria and highlight its potential as a promising microbial resource for postbiotic, antioxidant, and skin-barrier-enhancing applications. This study expands the ecological range of bifidobacteria and provides a genomic framework for evaluating flower-derived Bombiscardovia strains in cosmeceutical and functional food innovation.