Soy milk fermented by Bacillus subtilis SP-8-5 and Lactiplantibacillus plantarum 4_3 exhibits sedative-hypnotic ability in vivo

Jun 10, 2026Food research international (Ottawa, Ont.)

Fermented Soy Milk by Two Bacteria Shows Sleep-Helping Effects in Living Animals

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Abstract

Fermented soy milk demonstrated potential sedative-hypnotic ability in mice following specific fermentation processes.

Gavage administration of fermented soy milk significantly prolonged sleep duration induced by pentobarbital sodium in Kunming mice.
Slight increases in serum melatonin levels and reductions in glutamate and histamine were observed.
Significant neuronal activation was noted in the sleep-associated region of the hypothalamus.
Fermented soy milk altered gut microbiota composition, reducing the Firmicutes/Bacteroidota ratio and increasing beneficial probiotics.
Changes in γ-aminobutyric acid levels and neurotransmitter activity suggest a possible link between gut microbiota and sleep regulation.

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Fermented foods have many benefits, but the research on the sedative-hypnotic ability of fermented soy milk remains unclear. In this study, we found that the soy milk (1:8, w/v, dry soybeans : water) fermented with 1 × 10 CFU/mL Bacillus subtilis SP-8-5 for 24 h, followed by fermentation with 1 × 10 CFU/mL Lactiplantibacillus plantarum 4_3 for another 24 h exhibited potential sedative-hypnotic ability, as assessed by transcriptomics and HPLC. Animal experiments confirmed the sedative-hypnotic ability of fermented soy milk, and the results showed that gavage administration of the fermented soy milk to Kunming (KM) mice significantly prolonged the pentobarbital sodium-induced sleep duration time. The potential mechanism included slightly increasing the serum level of melatonin, slightly reducing the levels of glutamate and histamine, significantly increasing neuronal activation in the sleep-associated hypothalamic region, and significantly altering the microbiota composition in the feces of mice. The fermented soy milk reduced the Firmicutes/Bacteroidota ratio, increased the relative abundances of the probiotics Adlercreutzia equolifaciens and Lactiplantibacillus plantarum, and reduced the relative abundance of the potentially pathogenic bacterium Paraeggerthella hongkongensis in the feces and small intestinal contents of mice. We also identified the microorganisms that may be related to sleep regulation. The coordinated changes observed in the γ-aminobutyric acid level, gut microbiota composition, serum neurotransmitter levels, and hypothalamic neuronal activity (c-Fos induction) collectively suggest a potential involvement of the microbiota-gut-brain axis in mediating the sedative-hypnotic ability of fermented soy milk. This fermented soy milk could be used as a promising adjunctive therapy for the treatment of insomnia. 7 9

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Soy milk fermented by Bacillus subtilis SP-8-5 and Lactiplantibacillus plantarum 4_3 exhibits sedative-hypnotic ability in vivo

Abstract

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