Cytotoxicity screening and phylogeny of isolated lactic acid bacteria from cabbage kimchi samples

• Main Authors: Padilla, Angelo Jamerodd A., Constantino, Alianna Franczesca Y., De Leon, Anne Bernadette R., See, Ernest Gabriel C., Tomas, Jannah Miella V.
• Format: text
• Language: English
• Published: Animo Repository 2024
• Subjects: Lactic acid bacteria; Kimchi; Microbiology; Phylogeny; Fermented foods; Biology
• Online Access: https://animorepository.dlsu.edu.ph/etdb_bio/66
• Institution: De La Salle University

Colon cancer is one of the most common and fatal cancers in the Philippines. Currently, anticancer treatments are available but are known to produce serious side effects. This shows the need for alternatives, such as those derived from natural sources. In this study, lactic acid bacteria (LAB) were isolated from two cabbage kimchi products. Eleven (11) isolates from the two products were identified as Lactiplantibacillus plantarum (six isolates), Limosilactobacillus fermentum (one isolate), and Levilactobacillus brevis (four isolates) using phenotypic characterization and 16S rRNA gene (rDNA) sequencing. Phylogenetic analysis through maximum likelihood (ML) and neighbor-joining (NJ) methods both showed close evolutionary association among the six Lactiplantibacillus plantarum isolated from K1 kimchi. All Levilactobacillus brevis isolates from K2 kimchi were also found within the same clade, indicating close evolutionary association. Meanwhile, the Limosilactobacillus fermentum isolate from K1 kimchi was found to be more closely related with the Le. brevis isolates from K2. The secondary metabolites in the ethyl acetate extracts of the sterile culture supernatants of five (5) LAB isolates were assayed for their cytotoxic activities on colorectal adenocarcinoma (HT-29), colorectal carcinoma (HCT-116), normal liver epithelial (THLE-3), and normal human neonatal dermal fibroblast (HDFn) cell lines using the resazurin-based PrestoBlue™ reagent. The cell lines were exposed to two-fold serially diluted extracts with concentrations ranging from 1.09 µg/mL to 250 µg/mL for 72 hrs. Absorbance readings were taken at 570 nm and 600 nm after appropriate treatment with PrestoBlue™. The IC50, which is the concentration of the extract that inhibited 50% of the cells tested, was determined after computing the cytotoxicity index of each extract for the different cell lines. Results showed that all the extracts did not produce the IC50, indicating that these were not cytotoxic to the cell lines tested, in contrast to the results with the Zeocin positive control, which showed cytotoxicity to the different cell lines. It is recommended that the extracts from the LAB isolates be tested for other bioactivities such as cytotoxicity for other cancer cell lines, anti-oxidant, anti-inflammatory, and antimicrobial activities, since they were found to be nontoxic to the normal human cell lines THLE-3 and HDFn