Daidzein increased the density but not composition of Lactobacillus community in piglet digesta during in vitro fermentation as revealed by DGGE and dilution PCR

To investigate the effect of daidzein on Lactobacillus community change during in vitro fermentation, digesta from 12 conventionally raised piglets of the same litter with three on each slaughtering day were used as inocula in in vitro fermentation treatments: (a) VanSoest medium with 0.5 g of glucose and 50 mg·kg–1 of daidzein; (b) VanSoest medium with 0.5 g of glucose; (c) VanSoest medium only. After 48 h fermentation, DNA was isolated from culture pellets and Lactobacillus specific PCR primers, Lab0677r and Bact0011f, were used to selectively amplify 16S rDNA. V1-V3 regions of the lactobacilli 16S rDNA were further amplified using nested PCR with primers Univ0515rGC and Lab159f. PCR amplicons were analyzed using denaturing gradient gel electrophoresis (DGGE). All samples showed similar change in DGGE pattern after fermentation; some dominant bands disappeared and the density of some dominant bands obviously increased, suggesting that some species may be enriched while others may not be able to grow in the culture. DGGE patterns were different between digesta from different GI compartments either before or after fermentation, but no difference was observed between the treatments for each digesta sample. Dilution PCR with primers Lab0677r and Bact0011f was then applied to semi-quantify lactobacilli and showed that daidzein significantly increased the number of lactobacilli after 48h fermentation. A similar effect was observed with the plate counting method. In conclusion, daidzein did not affect Lactobacillus composition, but significantly enriched some Lactobacillus species, suggesting that daidzein may have the potential for use as a prebiotic substance in animal feed.