Lactulose promotes equol production and changes the microbial community during in vitro fermentation of daidzein by fecal inocula of sows

• Lactulose was used as equol-promoting prebiotic in vitro.
• Increasing equol production was found at lactulose with daidzein group at 24 h.
• Lactulose significantly changing the kinetics of fermentation in vitro.
• Microflora composition was altered by lactulose treatment.

Equol has higher biological effects than other isoflavones. However, only about 30–50% of humans possess a microbiota capable of producing equol from dietary daidzein. In recent years, interest has grown in dietary applications to improve equol production in human and other animals. In this study, lactulose was used as a potential equol-promoting prebiotic in vitro. The effect of lactulose on transformation of daidzein into equol by sows' fecal microbiota was investigated. Results showed that lactulose treatment improved bacteria growth parameters, changing the kinetics of fermentation in vitro. Lactulose significantly increased total gas production, T1/2, Tmax, and Rmax. Furthermore, lactulose altered the microflora composition, increased equol production associated with a reduction in the population of methanogen and increased the sulfate-reducing bacteria population during 24 h of incubation. Here, we report for the first time that in a certain condition (sealing or high pressure), via a dihydrodaidzein (DHD) pathway equol might be able to reform to daidzein by further metabolism using lactulose as a substrate. This study proposes that “hydrogen-producing prebiotic” might be a novel way to promote equol production in vivo or in vitro.