Toxicological Assessment of Oligofructans Derived from Raw Sugar Fermentation by Bacillus subtilis TISTR 001 and Their Modulatory Effects on Rat Gut Microbiota

Background/Objectives: Oligofructans are a category of non-digestible carbohydrates with beneficial effects on gut health and microbiota modulation. In this study, oligofructans were produced from raw sugar using Bacillus subtilis TISTR 001, and their safety and effects on the gut microbiota were assessed in rats. Methods: The acute toxicity assessment consisted of administering a single oral dose of 2000 mg/kg body weight (bw), whereas the subchronic toxicity assessment included oral dosages of 200, 600, and 2000 mg/kg/day for 90 days. Results: In the acute toxicity test, no mortality or toxicity was observed in the rats treated with a single dose of oligofructans during the 14-day observation period. The median lethal dose (LD50) of the oligofructans was >2000 mg/kg bw. In the subchronic toxicity study, daily oligofructans doses of 200, 600, and 2000 mg/kg bw for 90 days did not cause lethality or toxic clinical symptoms in rats of either sex. Furthermore, no treatment-related adverse effects of oligofructans on the hematological and biochemical parameters or organ histopathology were observed in the treatment and satellite groups. Hence, the no-observed-adverse-effect level (NOAEL) of oligofructans under the study’s test conditions was confirmed as 2000 mg/kg/day. Conclusion: No adverse effects were observed in either acute or subchronic toxicity studies at doses up to 2000 mg/kg/day. Moreover, oligofructans modulated the gut microbiota by promoting the growth of potentially beneficial commensal bacteria and reducing the taxa associated with inflammation or metabolic dysfunction. However, further studies are required to confirm these microbiome-related changes in humans.