Isolation, Identiifcation, Naringin Biotransforming Properties Of Naringinasc Producing Bacteria And Optimization Of The Conditions

Naringin (NI) is the main active ingredients of traditional Chinese herb pummelo peel.Naringenin (NE) is the dissociated aglycone of NI. NE has higher and wider biologicalactivities than NI. While chemical syntheses are available for high-level production ofNaringenin(NE), they typically involve toxic chemicals and extreme reaction conditionsthat can make the whole process difficult to scale.In our study, four bacterial strains, which we named AUH-JLD3, AUH-JLD7,AUH-JLD104and AUH-JLD109, capable of biotransforming naringin to naringenin wereisolated from human feces. The four isolated bacteria were identified as Blautia sp.AUH-JLD3, Enterococcus sp. AUH-JLD7, Bacteroides sp. AUH-JLD104andStreptococcus pasteurianus subsp. AUH-JLD109based on the16S rDNA sequenceanalysis, bacterial cell morphology, and biochemical traits. Study on biotransformingkinetics showed that all the four isolated bacterial strains were able to biotransformnaringin (0.2mmol/L) to naringenin within12h. The maximal concentration of thesubstrate naringin that strain AUH-JLD3, strain AUH-JLD7, strain AUH-JLD104andstrain AUH-JLD109were able to biotransform efficiently were0.2mmol/L (the averagebiotransforming rate was66.7%),0.8mmol/L (the average biotransforming rate was86.5%),0.2mmol/L (the average biotransforming rate was73.7%) and1.6mmol/L (theaverage biotransforming rate was93.2%), respectively. In summary, The facultativeanaerobic bacterium strain AUH-JLD109showed the highest naringin biotransformingability among all the four isolated bacterial strains. However, bacterium strainAUH-JLD109could grow and execute its naringin biotransforming activity only in theexpensive Brain Heart Infusion (BHI) medium.In order to futher improve the naringin biotransforming capacity by the bacterium strainAUH-JLD109, the co-cultured strain AUH-JLD109with Escherichia coli AUH-D2-1which was isolated and stored in our laboratory. The results showed that the maximalconcentration of the substrate naringin that strain AUH-JLD109were able to biotransformefficiently were increased to6.4mmol/L (the average biotransforming rate was97.4%, theaverage productivity of naringin was89.5%). Because the BHI medium is very expensive,we mixed different cheap components and made a cheap medium. The mixed medium wasoptimized by using orthogonal array design. The optimized medium was composed of: 1.2%of soluble starch,1.5%of peptone,0.5%of total phosphate(K2HPO4:KH2PO4=2:1),and0.05%of Fe2(SO4)3. The average naringin bioconversion rate was95.3%and theaverage productivity of naringin was86.4%. The cost of the optimized is20timesdecreased in comparison with that of BHI medium.Overall, for the first time we isolated four bacterial strains capable of biotransformingnaringin to naringenin from human intestinal microflora. The naringin biotransformingcapacity was significantly increased by co-culture of Streptococcus pasteurianus subsp.AUH-JLD109and Escherichia coli AUH-D2-1. In the mean time, the cost of medium wassignificantly decreased.