Preparation Of α-ketoglutaric Acid By Solid Fermentation And Functional Verification Of Fermentation Products

Alpha-ketoglutarate(AKG)is an important intermediate of the tricarboxylic acid cycle(TCA)cycle and glutamate metabolism.It not only plays an important role in promoting protein synthesis,promoting osteogenesis,delaying aging and anti-cancer,but also widely used in the chemical synthesis industry.At present,the methods on synthesis of AKG chemical are complex,and is likely to cause environmental pollution with many by-products during the industrialization process.Using microbial fermentation to produce AKG is a fast,green method.In the liquid fermentation process,excessive accumulation of AKG caused by thiamine deficiency and nitrogen source starvation has been reported.However,the process of mass production of AKG in solid fermentation has not been reported.In this paper,a strain of Bacillus subtilis capable of producing AKG was screened from 9 conventional fermentation strains(including lactic acid bacteria,yeast and Aspergillus).The solid fermentation conditions were optimized by Latin square design.The fermentation parameters were determined as follows: soybean meal: corn flour: bran =6:1:3;fermentation time was 48 hours;feed-water ratio was 1:0.8.Further regulation of the fermentation process using a metabolite(succinic acid)revealed that the yield of AKG could reach 0.3% when 1% succinic acid was added.Animal experiments were then used to feed a diet with 5% AKG-rich fermentation to study their effects on animal growth,gut health and immunity.The study found that the AKG-rich fermentation product has a tendency to reduce body weight and body weight gain,and can significantly increase the soleus muscle weight of mice(P<0.05),and significantly reduce the brown fat weight of mice(P<0.05).AKG-rich fermentation products had no significant effect on the length of villus and crypt depth in the ileum and jejunum of mice,but significantly increased the spleen weight of mice(P<0.05)and increased the weight of thymus(P=0.057).The resultsof blood routine and immunological indicators showed that the AKG-rich fermentationproducts can significantly reduce the percentage of neutrophils in the blood of mice(P<0.05),significantly increase the percentage of lymphocytes in the blood(P<0.05)and the average hemoglobin concentration of red blood cells(P<0.05),and can also significantly increase the phagocytic function of mouse monocyte-macrophages(P<0.05).This study is a positive exploration of the production of AKG by solid fermentation,and also provides a reference value for the production and application of metabolic intermediates for metabolic intermediates.