This study investigated the manufacturing of fermented soybean oil using a fermenting strain commonly processed for soybeans [Bacillus amyloliquefaciens (BA), Bacillus subtilis (BS), Lactobacillus acidophilus (LBA), and B. subtilis+L. acidophilus (BLO)] and evaluated its anti-obesity activities. Cytotoxicity of four kinds of fermented soybean oils was not observed in 3T3-L1 preadipocytes at 10 and 50 μg/mL. Triglyceride content was reduced by 20.6% in the BLO group at a treatment concentration of 50 μg/mL. The simultaneous treatment of fermented soybean oil and differentiation induction medium decreased PPARγ and C/EBPα gene expression at a concentration of 50 μg/mL and blocked adipocyte differentiation by increasing adiponectin gene expression. The inhibitory effect of adipocyte differentiation was greatest in the BLO group. C57BL/6J mice were examined for 4 weeks after being separated into seven groups [normal diet group (N), high fat diet group (C), group fed high fat diet combined with regular soybean oil (SO), group fed non-fermented soybean oil (NF), and groups fed high fat diet combined with 5% fermented soybean oil (BA, BS, LBA, and BLO)] to identify the effects of soybean oil on body weight, serum lipid, adiponectin, insulin, and leptin levels in mice with high fat diet-induced obesity. The body weight and serum lipid level of the C group increased drastically compared to those of the N group. In contrast, the group fed a diet combined with fermented soybean oil showed decreases in weight, serum total cholesterol, LDL-cholesterol, and triglyceride levels compared to those of the C group. Moreover, soybean oil was found to be effective in the BLO group. In conclusion, fermented soybean oil has positive effects in prohibiting adipocyte differentiation increased by high fat diet and improving serum lipid composition. Therefore, fermented soybean oil can be used as a functional food material with anti-obesity activity.

Keywords: 3T3-L1, anti-obesity activity, fermented soybean oil, differentiation