来自粪肠球菌E18的类恩特罗希斯丁菌素的部分纯化及特性分析

Abstract

Enterococcus faecium is a well-recognised producer of enterocins, ribosomally synthesised antimicrobial peptides with potential applications in food biopreservation. In this study, the bacteriocinogenic potential of E. faecium E18, a strain previously isolated from fermented foods, was investigated. The cell-free supernatant (CFS) inhibited the indicator strain Bacillus cereus ATCC 11778, with a maximum enterocin activity of 3200 ± 0 AU/mL (mean ± SD; n  = 3 biological replicates) recorded at 18 h, corresponding to the late exponential growth phase (absorbance at 600 nm, A₆₀₀ = 1.29 ± 0.05). Partial purification was achieved through ammonium sulfate precipitation, dialysis and methanol–chloroform extraction, resulting in a 36.5-fold purification and 16.0% recovery. The molecular mass of the antimicrobial peptide was estimated by Tricine–SDS–PAGE as approximately 3.5 kDa, and the most intense signal in the MALDI–TOF mass spectrum was observed at approximately m/z 3275, consistent with a class II bacteriocin. Under the conditions tested, the CFS retained detectable inhibitory activity after exposure to pH 3.0–9.0 and after heating at 100 °C for 15 min, and activity was abolished by proteolytic enzymes, indicating that the active compound is proteinaceous. PCR screening detected the entP structural gene, indicating the genetic potential for Enterocin P production, a class IIa pediocin-like bacteriocin; no amplification was obtained with the entA or entB primer pairs under the conditions tested. Taken together, these findings identify E. faecium E18 as an enterocin-producing strain whose Enterocin P-like bacteriocin merits further evaluation as a candidate natural antimicrobial agent for food safety and related biotechnological applications.