Aims Lactobacillus species are used widely as various food and supplements to improve health. Previous studies have shown that heat‐killed Lactobacillus brevis SBC8803 induces serotonin release from intestinal cells and affects sleep rhythm and the autonomic nervous system. However, the effect of SBC8803 on cognitive function remains unknown. Here, we examined the effects of dietary heat‐killed SBC8803 on hippocampus‐dependent memory and adult hippocampal neurogenesis. Methods Hippocampus‐dependent memory performance was assessed in mice fed heat‐killed SBC8803 using social recognition and contextual fear conditioning tasks. Adult hippocampal neurogenesis was evaluated before, during, and after feeding heat‐killed SBC8803 by measuring the number of 5‐bromo‐2‐deoxyuridine (BrdU)‐positive cells following systemic injections of BrdU using immunohistochemistry. Results Mice fed a heat‐killed SBC8803 diet showed an improvement of hippocampus‐dependent social recognition and contextual fear memories and enhanced adult hippocampal neurogenesis by increasing the survival, but not proliferation, of newborn neurons. Conclusion Dietary heat‐killed SBC8803 functions as memory and neurogenesis enhancers.

An antitumor polysaccharide SPR-901 was found in a fermented broth of a kind of lactic acid bacteria isolated from rice bran. SPR-901 is a high molecular alpha-glucan and its linkages are almost linear alpha-1,6 glucosidic ones with a small amount (ca. 5%) of branches at C-3 positions. It is a highly purified alpha-glucan and it contains no protein and no inorganic salts. SPR-901 showed significant antitumor activities against murine allogeneic and syngeneic tumors by both intraperitoneal and oral administration, and enhanced carbon clearance ability in mice, while it showed no direct cytotoxicities in vitro. The mechanism of antitumor activities of SPR-901 is supposed to be a host-mediated one, and this substance is classified as one of the biological response modifiers. These properties of SPR-901 were identical to those of RON, which was obtained from rice bran, therefore we concluded that these two polysaccharides were the same substance.

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