![]() Samples of dajiang (50 g) were collected at the end of fermentation. In April, the fermented soybean blocks are crumbled and mixed with salt in a jar for an additional fermentation step (20–30 days). The soybean paste blocks are usually produced during February. Fermentation occurs at room temperature for approximately 3–4 months. After cooling to 50 ☌ to 60 ☌ (4–6 h), the soybeans are ground into a paste and then formed into blocks (25–30 cm long, 15–20 cm high). In general, the soybeans are washed, soaked in water for 4–6 h, drained, and then steamed for 1 h. All samples were prepared in the same year using traditional methods. In this study, 14 samples of naturally fermented dajiang were collected from families in the city of Daqing in Heilongjiang Province, located in northeast China. Our results will contribute to a more comprehensive understanding of dajiang fermentation. Total DNA was extracted from the dajiang samples, and DGGE was performed using primers that correspond to the V3 region of 16S rDNA. In the present study, we used DGGE to study the bacteria ecology in naturally fermented dajiang obtained from Heilongjiang Province in China. However, few other studies have used this method, and more data are needed to better understand the dynamics of these bacterial communities. ( 2009) also used DGGE to investigate changes in the microbial community during a 12-week fermentation of natural Chinese soybean pastes. were the predominant species in Chinese samples. ( 2010) compared bacterial communities in five Japanese and three Chinese fermented soybean pastes using DGGE and showed that Tetragenococcus halophilus and Staphylococcus gallinarum dominated the bacterial microbiota in the Japanese samples, whereas Bacillus spp. Molecular fingerprinting by denaturing gradient gel electrophoresis (DGGE) is an effective method for studying bacterial community structures of fermented food products. Because of the known limitations of these methods, many recent studies have used culture-independent 16S rDNA-based polymerase chain reaction (PCR) techniques to assess the diversity and dynamics of microflora in this complex environment (Ercolini 2004). Most studies in China have used traditional culture-dependent methods to isolate and analyze bacterial populations involved in dajiang fermentation. Their results revealed a need to revise hygienic standards for soybean paste fermentation to reduce the numbers of Bacillus cereus. in commercially available naturally fermented soybean paste using the viable count method. ( 2008) analyzed lactic acid bacteria and Bacillus spp. ( 2004) isolated Lactobacillus delbrueckii, Pediococcus spp., and Bacillus spp. Besides molds and yeast, bacteria also play important roles in their fermentation. Previous studies have found that a wide range of microorganisms contribute to the production of fermented soybean paste products in China. Thus, interest is growing in fermented soybean products and the bacteria involved in the fermentation process. Similarly, fermented soybean extract has shown antigenotoxic and antioxidant activities (i.e., scavenging free radicals, inhibiting lipid peroxidation, and protecting against oxidative DNA damage Nam et al. Kobayashi ( 2005) has reported that another fermented soy product, soy sauce, may provide health benefits for individuals with allergic diseases because of its hypoallergenicity and antiallergic activity. The results reveal a high level of bacterial diversity in dajiang.ĭajiang is a fermented soybean paste that has been produced for centuries in villages of northeast China and is still popular today. Moreover, three uncultured bacterial clones were found in some samples and require further study. Potentially pathogenic Alphaproteobacteria and Staphylococcus epidermidis strains were also detected in this study. (including Bacillus firmus), Oceanobacillus spp., and Paenibacillus glycanilyticus in the dajiang samples may be due to their salt tolerance. in the Chinese fermented soybean paste dajiang using DGGE. ![]() This is the first report of Enterococcus spp. Our results indicate that lactic acid bacteria, including Lactobacillus plantarum, uncultured Leuconostoc mesenteroides, Leuconostoc gasicomitatum, Enterococcus faecium, and Tetragenococcus halophilus, were the predominant species. In this study, 14 samples of naturally fermented dajiang were analyzed by denaturing gradient gel electrophoresis (DGGE) to determine the diversity of the bacteria involved in fermentation. Although recent studies have revealed that a variety of bacterial species contribute to the production of fermented soybean products, little is known about bacterial communities involved in the fermentation of dajiang made in northeast China. Dajiang is a traditional fermented food prepared from soybeans that is still popular in northeast China.
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