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

Abstract

Aims: To isolate, characterize and identify lactic acid bacteria (LAB) in dochi (fermented black beans), a traditional fermented food in Taiwan. Methods and Results: 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 1157T. Conclusions: These results suggest that Ent. faecium is the main LAB present during the fermentation of dochi. Significance and Impact of the Study: This is the first report describing the distribution and varieties of LAB that exist in the dochi fermentation process.

Natural populations of lactic acid bacteria in douchi from Yunnan Province, China

“…Although these two commercial soybean foods are becoming more and more popular among people around the world, there are few reports about their LAB flora. Compared with factory-produced douchi from Taiwan, Yunnan douchi has a diverse population of LAB (Chen et al, 2006).…”

“…Five to ten LAB strains from MRS agar plates of each of the fermented douchi samples were randomly selected according to Harrigan and McMance (1976). All the isolates were cultured in MRS broth, and purified by replating on MRS agar plates (Chen et al, 2006). Prior to the molecular identification, the phenotypes of microbial isolates were determined based on colony and cell morphology.…”

“…Thus, LAB could contribute to food safety. Research has shown that LAB exist in fermented soybean food, such as tempeh and douchi in Taiwan (Moreno et al, 2002;Chen et al, 2006). It is important to define the exact composition of native douchi LAB and distinguish them down to the subspecies level, because this may raise the status of douchi, increase its marketability and profitability, and make it more commercializable.…”

Characterization of a Multiple-stress Tolerance Tetragenococcus halophilus and Application as Starter Culture in Chinese Horsebean-Chili-Paste Manufacture for Quality Improvement

“…Furthermore, halophilic LAB, the dominant LAB have been widely used as industrial starter to improve the quality or shorten the ripeness periods (Ogasawara et al, 2006). Among halophilic LAB, the genus Tetragenococcus was found in many fermented foods such as soy sauce, fish sauce, shrimp, and fermented black beans (Chen et al, 2006;Fukami et al, 2004;Udomsil et al, 2011) and it comprised five species: T. halophilus, T. muriaticus, T. solitaries, T. koreensis and T .osmophilus (Justé et al, 2008). The bacteria species could grow in 18% NaCl or greater, and produced numerous volatile compounds (Udomsil et al, 2011;Udomsil et al, 2010).…”

Scientific Opinion on the safety of a ‘fermented black bean extract (Touchi extract)’ as a Novel Food ingredient

“…Fermented black beans are also commonly referred to as "Touchi" in Japan (Fujita and Yamagami, 2007) and Douchi in Taiwan and China (Chen et al, 2006).…”