Molecular identification and relative abundance of microorganisms in douchi koji and salted egg white sufu during...

A novel animal protein-based douchi koji-inoculated steamed salted egg white sufu (SEWS) has been developed. This study determined the relative abundance of microorganisms in the douchi koji and semi-finished (5-day fermentation) and finished (5-day fermentation and 14-day ripening) SEWS by using 16S and 18S ribosomal DNA and gene-cloning methods. The results revealed that Bacillus spp. and Aspergillus oryzae were dominant in the douchi koji. In the semi-finished SEWS, the percentages of Bacillus amyloliquefaciens and Bacillus subtilis were considerably lower, whereas those of Enterococcus and Staphylococcus were substantially higher. In the finished SEWS, Bacillus spp. became dominant again and A. oryzae was the only fungus detected. In conclusion, by using molecular techniques, microbial population dynamics in SEWS can be evaluated. During processing, the relative abundance of microorganisms in SEWS changed and Bacillus spp. and A. oryzae remained dominant. This study provides crucial information for designing starter cultures for producing SEWS.