Anti-Inflammatory and Selective Anticancer Activities of Supernatants from Lactiplantibacillus plantarum S61 Fermented on Glucose and Xylooligosaccharides

This study aimed to evaluate the biofunctional and selective anticancer potential of cell-free supernatants obtained from Lactiplantibacillus plantarum S61 fermented on two carbon sources: glucose (Glu) and xylooligosaccharides (XOS). High-performance liquid chromatography (HPLC) analysis revealed significant production of vitamin B2 (8.66 ± 0.11 and 8.05 ± 0.06 mg/L for Glc and XOS, respectively) and vitamin B12-like compounds (0.47 ± 0.03 and 0.24 ± 0.03 mg/L, respectively). The anti-inflammatory activity was assessed by inhibition of bovine serum albumin (BSA) denaturation, where XOS-fermented supernatants exhibited the strongest effect (88.7 ± 0.1% at 400 µg/mL), comparable to diclofenac (91.44 ± 0.1%), while Glc reached 71.1 ± 0.4%. The anticancer activity was evaluated in vitro using the MTT assay on two breast cancer cell lines (MCF-7 and MDA-MB-231) and normal peripheral blood mononuclear cells (PBMCs). Both fermented supernatants showed a dose-dependent cytotoxic effect against cancer cells while exhibiting markedly lower toxicity toward PBMCs, indicating a selective anticancer activity. XOS-fermented supernatants displayed lower IC₅₀ values against MCF-7 (198.55 ± 14.94 µg/mL) and MDA-MB-231 (200.80 ± 13.61 µg/mL) compared to PBMCs (862.16 ± 169.11 µg/mL), resulting in favorable selectivity index values. Overall, these findings highlight the potential of L. plantarum S61 postbiotic metabolites, particularly those derived from XOS fermentation, as safe and selective natural agents with anti-inflammatory and anticancer properties.