Microbial interaction between human skin and Nukadoko, a fermented rice bran bed for pickling vegetables

Abstract The skin microbiome, which varies widely between individuals, plays a crucial role in human health. It also interacts with the environment in various ways, including during the preparation of fermented food. Nukadoko is a pickle and traditional fermented food in Japan that utilizes lactic acid bacteria to ferment vegetables. The microbial composition of Nukadoko contributes to the flavor of pickled products. However, the origin of the microbes present in the rice bran bed has yet to be determined and no studies have examined how the skin microbiome affects the quality of Nukadoko . In this study, the effects of interaction of microbes between Nukadoko and the human skin during Nukadoko maintenance were studied. Three participants were asked to stir commercially available late-stage Nukadoko for 14 days and not stir it for the remaining 14 days to examine microbial settlement and shedding. Microbiome analysis was performed on human skin and Nukadoko . We found that microorganisms from rice bran beds can temporarily settle on human skin but are shed quickly. Stirring rice bran beds by hand may have short-term effects on the skin microbiome. This study provides insights into the communication between human and food microbiomes in traditional Japanese fermented foods.