Antibacterial and Antibiofilm Properties of Postbiotics Derived from Lactiplantibacillus pentosus B1

Lactic acid bacteria (LAB) are a promising source of postbiotics with potential applications in the cosmetic industry; however, strains isolated from fermented vegetables are rarely studied. This study aimed to characterize the bioactivity of postbiotics produced by <i>Lactiplantibacillus pentosus</i> B1 isolated from fermented beetroot juice. An organic extract (ELCFS) and a lyophilizate (LLCFS) were prepared from cell free supernatant of B1 and assessed for antimicrobial activity (MIC, MBC), biofilm inhibition and eradication ability against <i>Staphylococcus aureus</i>, <i>Escherichia coli</i>, <i>Streptococcus pyogenes</i> and <i>Cutibacterium acnes</i>. Stability (temperature, time) and cytotoxicity were also examined. Metabolite composition was determined by GC-MS. MIC values were 10 g/L for ELCFS and 10-20 g/L for LLCFS. ELCFS completely inhibited biofilm formation at 10 g/L, and LLCFS at 25 g/L; partial inhibition was observed at lower concentrations (e.g., <i>E. coli</i>-32.99% at 1 g/L ELCFS; <i>S. aureus</i> and <i>S. pyogenes</i>-74.01% and 95.67%, respectively, at 5 g/L). Complete eradication of mature biofilm was obtained at 2.5 g/L (ELCFS) and 12.5 g/L (LLCFS), while a significant partial effect was observed from 0.04 g/L ELCFS for <i>E. coli</i> (29.3%) and 0.2 g/L LLCFS for <i>S. pyogenes</i> (23.2%). <i>C. acnes</i> showed the lowest sensitivity. A reduction in viability of eucaryotic cells was observed at ≥ 5 g/L ELCFS (90.32%) and 12.5-50 g/L LLCFS (55.87-89.20%). Importantly, concentrations causing partial inhibition and eradication of biofilm did not show cytotoxicity towards fibroblasts. The preparations were thermostable and retained activity over time; only incubation of ELCFS at elevated temperature significantly reduced its antimicrobial activity against the <i>C. acnes</i> strain. GC-MS analysis revealed five organic acids, with lactic acid dominating. The results confirm the potential of <i>L. pentosus</i> B1 as a source of stable, effective, and safe postbiotics for cosmetology applications.