4.2.1. Microbiome Samples Collection from the Study Participants
A total of 132 skin microbial swab samples were collected by dividing two sites (control and postbiotic treatment sites) from the faces of healthy Korean women using the NBgen-GUT NP self-collection tube (Noble Biosciences, Republic of Korea). The participants applied the postbiotics-containing test product or the control product on the randomly assigned sides of the entire face. The microbiome swab was collected in an area of 4 cm x 5 cm on each side of the face, starting 1 cm below the lowest point of the lower eyelid, and 1 cm next to the nasal ala. All collected clinical samples were stored at −80 °C before being used in further steps. The clinical specimen collection in this study (skin microbiota samples collection) was approved by the ethics committee of Global Medical Research Center (IRB numbers: GMRC-22425-EA1). All clinical processing applied in this study was conducted under the guidelines and regulations of the Helsinki Declaration.