Isolation and characterization of lactic acid bacteria from dochi (fermented black beans), a traditional fermented food in Taiwan

Abstract

To isolate, characterize and identify lactic acid bacteria (LAB) in dochi (fermented black beans), a traditional fermented food in Taiwan. A total of 30 samples were collected from three different dochi producers and analysed after different periods of storage. Fifty-two cultures of LAB were isolated from dochi samples and the isolates were divided into classes by phenotype and then into groups by restriction fragment length polymorphism analysis and sequencing of 16S ribosomal DNA. Phenotypic and biochemical characteristics identified six different bacterial groups (A-F) and showed that the majority of the isolates were homofermentative LAB. Enterococcus faecium was the most abundant of the dochi-isolated LAB. All isolated LAB were able to grow in MRS broth containing 6% NaCl, but only Enterococcus, Pediococcus and Tetragenococcus species could grow in MRS broth containing 10% NaCl. Furthermore, antibacterial activities of isolates were determined, and four isolates showed inhibitory activities against the indicator strain Lactobacillus sakei JCM 1157(T). These results suggest that Ent. faecium is the main LAB present during the fermentation of dochi. This is the first report describing the distribution and varieties of LAB that exist in the dochi fermentation process.