Abstract: A new strain with broad-spectrum antimicrobial activity, named as HLR-13, was isolated from traditional smoked bacon from Hunan province. The cell-free supernatant produced by the strain HLR-13 showed a high inhibitory activity towards many foodborne pathogenic bacteria and fungi such as Bacillus cereus, Pseudomonas fluorescens, Mirococcus luteus, and Salmonella enteritidis. Based on its morphological, physiological and biochemical characteristics as well as 16S rDNA sequence analysis, the strain HLR-13 was identified as Bacillus subtilis subsp. spizienii. Then the antimicrobial protein produced by the strain was isolated and purified through ammonium sulfate precipitation, ion exchange chromatography (Q Sepharose FF) and gel filtration chromatography (Sephadex G-75). Sodium dodecyl sulfate- polyacrylamide gel electrophoresis (SDS-PAGE) revealed a single band and the antimicrobial protein was preliminary identified as a hypothetical protein with molecular weight of 31 494 Da by matrix-assisted laser desorption ionization time-of-flight tandem mass spectrometry (MALDI-TOF-MS/MS) analysis through comparison with NCBI non-redundant (NR) protein database. This research can provide a theoretical basis for developing new biological preservatives.

Key words: Bacillus subtilis subsp. spizienii, antimicrobial protein, strain identification, isolation, purification