A high-throughput screening effort, designed to isolate bacteriocin-producing lactic acid bacteria (LAB) from malted cereals, resulted in the isolation of four bacteriocin-producing strains that could not be assigned conclusively to recognized species. The four isolates (UCC128T, UCC125, UCC126 and UCC127) were found to share identical (100%) 16S rRNA gene sequences and were therefore deemed to belong to the same species. The strains were Gram-positive, catalase-negative, non-motile homofermentative LAB. The closest recognized relative to strain UCC128T identified based on comparative 16S rRNA gene sequence analysis was Lactobacillus mali DSM 20444T (97% similarity). The strains were characterized phenotypically to identify specific growth requirements. DNA-DNA hybridization between strain UCC128T and L. mali DSM 20444T revealed a level of relatedness of only 39.4%. This indicates that strain UCC128T does not belong to the species L. mali. The four bacteriocin-producing strains are therefore considered to represent a novel species of the genus Lactobacillus, for which the name Lactobacillus hordei sp. nov. is proposed. The type strain is UCC128T (=DSM 19519T=LMG 24241T).