This is the first report of a bacteriocin being produced by lactobacillus acidophilus ATCC 4356. For protein identification, the ~8-kDa peptide band was removed from the acrylamide gel and digested in-gel by trypsin, and the resulting peptide fragments were extracted and analyzed by LC-MS/MS analysis. The MS data were processed using Thermo Proteome Discoverer software (v2.2) with the SEQUEST search engine. Three peptides, VAHCASQIGR (amino acids 23-32), GSAACVSYLTR (amino acids 69-79), GSAACVSYLTRHRHH (amino acids 69-83) were identified as tryptic fragments on the basis of LC-MS/MS.This is the first report of a bacteriocin being produced by lactobacillus acidophilus ATCC 4356. For protein identification, the ~8-kDa peptide band was removed from the acrylamide gel and digested in-gel by trypsin, and the resulting peptide fragments were extracted and analyzed by LC-MS/MS analysis. The MS data were processed using Thermo Proteome Discoverer software (v2.2) with the SEQUEST search engine. Three peptides, VAHCASQIGR (amino acids 23-32), GSAACVSYLTR (amino acids 69-79), GSAACVSYLTRHRHH (amino acids 69-83) were identified as tryptic fragments on the basis of LC-MS/MS.