Characterization of an antimicrobial substance produced by Lactobacillus plantarum NTU 102

Lactic acid bacteria (LAB) are used in a variety of bio-industrial processes, including milk fermentation, and have been reported to have bactericidal activities. We previously isolated Lactobacillus plantarum NTU 102 from homemade Korean-style cabbage pickles. The aims of this work were to perform a screen of the antimicrobial substances produced by L. plantarum NTU 102 and to characterize it.

In this study, we investigated the bactericidal activity of this LAB strain and demonstrated that the cell-free supernatant of L. plantarum NTU 102 had antimicrobial activity.

The antibacterial activity was significantly decreased by proteolytic enzymes, including pepsin, proteinase K, and trypsin, suggesting that the antimicrobial substance had proteinaceous properties. Additionally, this activity was heat stable and not affected by alterations in the pH from 1.0 to 4.0. The antibacterial substance produced by L. plantarum NTU 102, which we named LBP102, exhibited a broad inhibitory spectrum. The active compound was identified by nuclear magnetic resonance (NMR) techniques (¹H NMR and ¹³C NMR). The IUPAC name was 2-(2-1 mino-1-hydroxyethoxy) ethyl 2-methylpropanoate. The substance showed antibacterial activity against Vibrio parahaemolyticus, and completely inhibited the growth of V. parahaemolyticus on agar plates at a concentration of 75 μg/mL.

The proposed antimicrobial substance, LBP102 was found to be effective against V. parahaemolyticus BCRC 12864 and Cronobacter sakazakii BCRC 13988. The remarkable effects of LBP102 against this and other pathogens indicated its potential as a natural preservative/food additive.