Angiotensin I-converting enzyme inhibitory activity of natto, a traditional Japanese fermented food

Abstract

We evaluated angiotensin I-converting enzyme (ACE) inhibitory activities in raw soybeans, soaked soybeans, steamed soybeans, the substance exuded from soybeans during steaming and a series of natto samples which were produced with different fermentation times. We also compared the ACE inhibitory activities of natto produced using commercial bacterial strains and natto produced using strains obtained from dried rice plants. We found that the ACE inhibitory activity of natto varied depending on fermentation time. Furthermore, it was shown that fermentation with certain dried rice plant extracts resulted in natto with higher ACE inhibitory activity than that produced using commercial bacterial strains. It is suggested that some ACE inhibitory substances in natto are derived from the steamed soybeans used during production, while others are formed from steamed soybean components during fermentation.