Purification, identification, and characterization of a novel bioactive peptide LP-15 with antimicrobial and antioxidant activities produced by Lactobacillus pentosus BL-15 isolated from Asterias.

Bioactive peptides from lactic acid bacteria (LAB) are gaining attention as natural antimicrobial and antioxidant agents for food applications. In this study, a novel bioactive peptide, LP-15, derived from Lactobacillus pentosus BL-15 isolated from Asterias collected on Naozhou Island, China, was characterized. The cell-free supernatant of strain BL-15 displayed antimicrobial activity against Gram-positive bacteria (Staphylococcus aureus, Bacillus subtilis, and Listeria monocytogenes) and Gram-negative bacteria (Escherichia coli and Vibrio parahaemolyticus), as well as antioxidant activities including DPPH, hydroxyl radical scavenging, ABTS radical scavenging, and total reducing capacity assays. Based on these results, strain BL-15 was selected for peptide purification. Peptide LP-15 was purified using ethyl acetate (EtOAc) extraction, SP-Sepharose Fast Flow cation exchange chromatography, Sephadex LH-20 gel chromatography, and reversed-phase high-performance liquid chromatography (RP-HPLC), which exhibited antimicrobial activity against L. monocytogenes and notable antioxidant activity (DPPH radical scavenging rate: 78.72%). Mass spectrometry identified LP-15 as an 11-amino-acid peptide (LEVQAVSKNKL) with a molecular weight of 1279.66 Da, showing ~ 90% sequence similarity to the protein G2/mitotic-specific cyclin-B. LP-15 retained antimicrobial and antioxidant activities after heat and UV treatments and remained stable over a pH range of 2 ~ 6. These findings highlight LP-15 as a promising natural preservative candidate for food applications.