Determination of microbial diversity in meju, fermented cooked soya beans, using nested PCR-denaturing gradient gel electrophoresis

Abstract

To identify the microbiota in meju, fermented cooked soya beans, that may directly affect the microbial communities of Korean fermented soya bean foods. Using conventional bacterial 16S rDNA, bacilli-specific 16S rDNA or fungi 18S rDNA-specific primers, PCR products were amplified through a series of PCRs using the DNA extracted from ten meju samples. The amplicons were analysed using denaturing gradient gel electrophoresis (DGGE), which showed that Enterococcus durans was commonly detected in nine of ten meju samples. Bacillus subtilis was shown to be the major strain of bacilli in the samples tested. Based on the DGGE analysis of fungi in meju, we determined that Absidia corymbifera, Aspergillus sp. and Candida rugosa were the main fungi in the tested samples. A variety of bacterial and fungal micro-organisms were identified in meju samples, in addition to the micro-organisms already known to be present. This is the first report showing the differences and similarities in the populations of micro-organisms in meju samples using nested PCR-DGGE, a culture-independent method. The results may be applicable to the development of improved meju, in which the indigenous micro-organisms required for fermentation can be standardized.