The sake yeast strain “KODO” was isolated from the soil of Kumano Kodō, a world heritage site, and has been used in sake fermentation. In this study, we bred the strain to enhance the productivity of ethyl caproate, which is one of the important flavor compounds of ginjo-shu. The concentrations of ethyl caproate of test brewing sake fermented by bred yeasts were 8–10 fold higher than that of the parental KODO strain. Furthermore, the concentrations of acetic acid of test brewing sake fermented by bred yeasts were 1/3–1/5 fold lower than that of the parental KODO strain. “KODO.ec 162”, one of the bred yeasts, has been used for sake fermentation since 2021.

Rice vinegar is a common condiment in Japan, and the submerged fermentation method is used for the industrial production of rice vinegar. Acetic acid bacteria are known to have a significant influence on fermentation characteristics during vinegar brewing, and clarification of the types of microorganisms and their roles in acetic acid fermentation in submerged fermentation rice vinegar production may be useful for optimization of the fermentation process. In this study, we investigated the changes in the microbiome in submerged fermented rice vinegar for the entire fermentation process, which has not been investigated before. The investigation of the bacterial community showed that the percentage of acetic acid bacteria of the genus Komagataeibacter increased rapidly when the ethanol concentration started to decrease, then maintained a high percentage of dominance in both rice vinegars with different acidity levels. Metagenomic analysis results for the starter culture suggested that the acetic acid bacteria that ferment in submerged fermented rice vinegar is Komagataeibacter europaeus, which is resistant to high acetic acid concentration, and that this strain is closely related to the strain isolated from submerged fermented vinegar produced in Europe. This study provides basic information on the microorganisms in submerged fermentation of rice vinegar and may be useful for optimizing the fermentation process in rice vinegar brewing.

In this study, changes in methiin content in Chinese chives due to different freezing packaging methods were investigated using high-performance liquid chromatography. The results showed that freezer bags or plastic wraps had no effect on the methiin content of Chinese chives after freezing. On the other hand, when newspaper was used, the methiin content was affected by the packaging thickness. This is thought to be because when Chinese chives were wrapped in thin newspaper, their cells and tissues deteriorated due to water evaporation from the chives, and as a result, the extraction efficiency of methiin with ethanol was improved.