Previous work has linked members of the genus Corynebacterium in the skin microbiota with aspects of skin health, but the direct effects of Corynebacterium-derived metabolites on skin cells have been underexplored. The present study aimed to isolate Corynebacterium strains from human facial skin and screen their ferment filtrates for bioactivities relevant to skin improvement, specifically effects on extracellular matrix genes and melanin production. The authors used a combination of targeted gene expression assays, melanin biosynthesis assessment in a melanocyte model, mass spectrometry profiling, and transcriptome analysis to identify and functionally characterize active postbiotic compounds.
The investigators isolated eight Corynebacterium strains from the facial skin of a female participant. To evaluate potential skin-improving effects, the researchers prepared culture supernatants (ferment filtrates) from each isolate and applied them to three established skin-relevant cell lines: Hs68 (dermal fibroblast), HaCaT (keratinocyte), and B16-F10 (murine melanocyte). The screening panel measured changes in expression of extracellular matrix and skin function genes — ELN (elastin), COL1A1 (type I collagen alpha 1), IL-1β (inflammatory cytokine), and HAS3 (hyaluronan synthase 3) — and assessed each filtrate's ability to inhibit melanin biosynthesis in the B16-F10 model. These endpoints were chosen to capture potential effects on skin aging, barrier and hydration function, inflammation, and pigmentation.
Among the eight isolates, the strain designated Corynebacterium amycolatum SB-1 was selected as the lead candidate for further analysis. The selection criteria reported in the source were primarily pragmatic: SB-1 exhibited a relatively rapid growth rate and produced a high cell yield during culture, facilitating downstream biochemical and analytical work. The choice of SB-1 enabled more extensive chemical profiling of its ferment filtrate and functional testing of candidate bioactive molecules.
To identify postbiotic components in the SB-1 ferment filtrate, the investigators applied liquid chromatography–time-of-flight mass spectrometry (LC-TOF/MS) screening. This analysis detected ellagic acid, a known polyphenolic antioxidant, among the compounds in SB-1 fermentate. The authors highlight ellagic acid for further functional validation because of its documented antioxidant properties and reported anti-melanogenic activity in other contexts, making it a plausible mediator of the observed effects on pigmentation and extracellular matrix gene expression.
Following the LC-TOF/MS identification, ellagic acid was tested directly on skin cell models to validate its effects. The authors evaluated expression of the FLG gene (filaggrin) as a keratinocyte differentiation and barrier-related marker, and they measured melanin biosynthesis inhibition in the B16-F10 melanocyte model. Across these assays, ellagic acid demonstrated activity consistent with skin benefit: it inhibited melanin production and influenced gene expression related to collagen and barrier function. In the screening step with whole SB-1 ferment filtrate, the original panel genes — ELN, COL1A1, IL-1β, and HAS3 — had been monitored to compare isolates, and ellagic acid was subsequently investigated as a likely active constituent responsible for beneficial transcriptional and functional changes.
To further elucidate mechanisms, the study performed RNA sequencing on cells exposed to ellagic acid. Transcriptomic analysis indicated that ellagic acid is significantly involved in pathways that suppress melanogenesis and promote collagen synthesis. The authors report that these global gene expression changes align with the targeted assay findings: reduced melanin biosynthesis is concordant with downregulation of melanogenic pathways, while enhanced collagen-related signals match upregulation of genes such as COL1A1. The combined targeted and transcriptomic data support a model in which ellagic acid from the SB-1 ferment filtrate acts on multiple skin-relevant pathways to reduce hyperpigmentation and favor extracellular matrix maintenance.
The authors conclude that ellagic acid derived from Corynebacterium amycolatum SB-1 ferment filtrate is a promising bioactive compound for skin improvement, with effects directed at inhibiting melanogenesis and promoting collagen synthesis. Their multi-step approach — isolation, screening in fibroblast/keratinocyte/melanocyte models, mass spectrometry identification, targeted gene assays, and RNA sequencing — provides converging evidence that ellagic acid mediates beneficial transcriptional and functional changes in cultured skin cells. The work positions SB-1 ferment filtrate and its ellagic acid content as potential candidates for development as topical postbiotic or active ingredients aimed at hyperpigmentation and skin aging.
This report is a preprint and has not been certified by peer review; the authors explicitly note the preprint status. The source does not provide detailed quantitative results, experimental replicates, concentration-response relationships, safety or formulation data, or in vivo validation within the abstract. Where the source omitted specifics (for example, exact assay values, time points, or concentrations used), those details were not reported and therefore are not summarized here. The authors declared no competing interests.
Overall, the study provides an initial, preclinical characterization that links a skin-derived Corynebacterium strain to production of ellagic acid, and presents cell-culture and transcriptomic evidence supporting anti-melanogenic and collagen-promoting activities. Further peer-reviewed work will be required to confirm efficacy, define mechanisms in detail, and assess translational potential for topical applications.