A Gram-positive, endospore-forming, lactic acid bacterium was isolated from spoiled orange juice. The organism, strain QC81-06(T), grew microaerobically or anaerobically at 30-45 degrees C (optimum 35 degrees C) and pH 3.5-5.5 (optimum pH 4.5), and produced acid from various sugars. D-Lactic acid was produced. It contained menaquinone-7 as the major isoprenoid quinone. The G+C content of the genomic DNA was 47.5 mol%. The predominant cellular fatty acids of the strain were iso-C(16 : 0), anteiso-C(15 : 0) and anteiso-C(17 : 0). Phylogenetic analyses based on the 16S rRNA gene and gyrB gene (DNA gyrase B subunit gene) revealed that strain QC81-06(T) clustered with Sporolactobacillus species but the strain was clearly distinct from other Sporolactobacillus species with significant bootstrap values. The levels of 16S rRNA gene and gyrB gene sequence similarities between strain QC81-06(T) and the other strains of the cluster were 96.0-97.0 % and 75.1-77.2 %, respectively. On the basis of these results, strain QC81-06(T) should be classified as a novel Sporolactobacillus species for which the name Sporolactobacillus putidus is proposed. The type strain is strain QC81-06(T) (=DSM 21265(T)=JCM 15325(T)).