Abstract: In order to study the synergistic effects of lotus seed resistant starch (LRS) as a prebiotic and sodium lactate (SL) as a postbiotic on the intestinal flora and metabolic profile of rats, 24 male SD rats were randomly divided into normal control (NC), LRS, SL, and LRS + SL groups. After four weeks of oral administration, the diversity of intestinal flora and differential metabolites were analyzed by high-throughput gene sequencing and non-targeted metabolomics, respectively. The results showed that LRS, SL and their combination could increase the richness of intestinal flora. Compared with the NC group, the relative abundance of Lachnospiraceae_NK4A136_group was increased, while the relative abundance of Coriobacteriaeae_UCG-002 and Enterrhabdus in the small intestine of rats was decreased in the LRS group; in the SL group, the relative abundance of Lactococcus and unclassified_f__Micrococcaceae was decreased increased, respectively; in the LRS + SL group, the relative abundance of unclassified_f__Ruminococcaceae and Lachnospiraceae_NK4A136 was increased, whereas the relative abundance of Vagococcus and Allobaculum was decreased. Compared with the LRS and SL groups, the relative abundance of Allobaculum was decreased, while the relative abundance of unclassified_f__Ruminocaceae was increased. The non-targeted metabolomic analysis showed that the levels of (R)-lipoic acid, α-curcumin, ginkgolide A, cervonoyl ethanolamide and steroid hormones in the small intestine of rats in the LRS group were up-regulated, while the levels of LysoPC(17:0) and L-serine were down-regulated compared with the NC group, and there were significant differences in steroid hormone metabolic pathways between the two groups. In the SL group, cervonoyl ethanolamide was up-regulated, and the metabolic pathways of steroid hormones and bile acids changed significantly. In the LRS + SL group, pantothenic acid was up-regulated, whereas LysoPC(17:0) was down-regulated, and amino acid metabolic pathways changed significantly. There were significant differences in metabolic pathways of lipid, bioactive substances and vitamin between the LRS + SL group and the LRS and SL groups. Intervention with LRS and SL could optimize the structure of intestinal flora and inhibit the reproduction of potentially harmful bacteria, thereby promoting the increase of potentially beneficial metabolites. The combination of LRS and SL was more effective in increasing the diversity of intestinal flora, regulating vitamin metabolism, amino acid metabolism and lipid metabolism, and enhancing the defense system in the body. These results will provide a theoretical basis for studies on the synergistic effects of prebiotics and postbiotics.

Key words: lotus seed resistant starch; sodium lactate; postbiotics; intestinal flora; non-targeted metabolomics