Transition and diversity of bacterial flora found in traditional fermented foods

Many fermented foods are produced in Japan, and the preparation conditions are set very carefully so that strict microbial control can be carried out. Even the manufacturing methods of them have been developed empirically, specific microorganism is established to be reproduced well in the fermentation medium of each food from ancient times. Although the history of bacterial flora research of fermented foods is old, it has become possible to obtain more detailed information by development of high-throughput 16S rRNA gene analysis using next-generation sequencing. Analysis of the bacterial flora of the fermented food of Ishikawa prefecture, Japan, showed that various bacterial species are intermingled among the fermented products, and that sometimes different kinds of bacteria became dominant even for the same type of food. Lactobacillus sakei, which is known as the predominant lactic acid bacterium in Japanese sake starter, prominently proliferated in “kaburazushi” that contains rice koji, which is a shared ingredient among the both foods. Six “narezushi” products obtained from Noto peninsula were found to be dominated by various Lactobacillus and Pediococcus species. In “yamahai-moto”, nitrate-reducing bacteria normally found in the early stage of fermentation was hardly detected, while Lactobacillus acidipiscis was present at the stage. This review illustrates, through introducing several case studies, how the bacterial flora of fermented foods are robustly and/or variably controlled to achieve the final dominance of lactic