Effects of α-ketoglutaric acid produced by solid fermentation on mouse growth, intestinal structure and immune function

Objective  To screen strains for producing α-ketoglutaric acid by solid fermentation, and study the effects of fermentation products on animal growth, intestinal structure and immune function.

Method  Nine strains (including lactic acid bacteria, yeast and Aspergillus) were fermented and α-ketoglutaric acid content in the fermentation products was detected. Succinic acid was added during the fermentation to study its effect on the production rate of α-ketoglutaric acid. Subsequently, sixteen 4-week-old C57/BL mice were randomly divided into two groups, 5% normal fermented material or 5% α-ketoglutarate-rich fermented material was added to the common diet for four weeks. Animal feeding and growth, intestinal structure, and phagocytosis and blood picture of monocyte-macrophages were analyzed.

Result  The solid fermentation of yeast produced a trace amount of α-ketoglutaric acid, Bacillus subtilis produced about 60 μg/g α-ketoglutaric acid, and α-ketoglutaric acid was not detected using other strains. The addition of succinic acid to the solid fermentation of Bacillus subtilis promoted the accumulation of α-ketoglutaric acid with the maximum production rate of 0.3%. Dietary supplementation of 5% targeted α-ketoglutarate fermentation product slightly reduced body weight and body weight gain of mice(P>0.05), significantly increased the soleus muscle weight of mice (P<0.05), and significantly reduced brown fat weight in mice (P<0.05). The fermentation product had no significant effect on the villus length and crypt depth of mouse ileum and jejunum. Blood and immunological indicators revealed thatα-ketoglutarate-rich fermentation product significantly reduced the percentage of neutrophils, increased the percentage of lymphocyte, and increased the content of red blood cell hemoglobin. Moreover, the fermentation product also significantly increased the phagocytic function of mouse monocyte-macrophages (P<0.05).

Conclusion  The addition of succinic acid can promote accumulation of α-ketoglutaric acid in the solid fermentation process of Bacillus subtilis. Adding α-ketoglutarate-rich fermentation in the diet can significantly increase the muscle weight, decrease the fat weight of mice, and significantly improve the immune function of mice.