Isolation, Identification And Biotransforming Property Of Isoflavone Biotransforming Bacteria Isolated From Rabbit Feces

Soy isoflavones are the secondary metabolites which belong to flavonoid produced bysoy and other Papilionoideae plants. Soy isoflavones are mainly distributed in very fewplants, such as soybeans, alfalfa, etc. To date, there are12soy isoflavones, including threekinds of aglycones, i.e. daidzein, genistein and glycitein and the other nine kinds existingin the form of glycoside. In vivo test showed that soy isoflavone glycosides ingested bymammalian can be hydrolyzed to daidzein by glycosidase enzyme produced by intestinalmicroflora, or absorbed directly by the organism, or soy isoflavones soybean glycosidesare degraded into different metabolites, such as dihydrodaidzein (DHD), equol andO-desmethylangolensin (O-Dma), dihydrogenistein (DHG) and5-hydroxy-equol(5-hydroxyequol).In this study, we isolated two bacterial strains which we named AUH-JLR41andAUH-JLR23from rabbit feces. These two bacterial strains were able to convert soyisoflavones. Blast search revealed that the complete16S rDNA gene sequence ofAUH-JLR41(KJ188150) has99.6%similarity to that of Slackia equolifaciens DZE(EU377663), and the complete16S rDNA gene sequence of AUH-JLR23(KJ188151) has97.12%similarity to Clostridium sp. TM-40(AB249652). Based on the analysis of the16SrDNA sequences, cell morphology and Gram staining, the strain AUH-JLR41wasidentified as Slackia sp. AUH-JLR41, and the strain AUH-JLR23was identified asClostridium sp. AUH-JLR23.The high performance liquid chromatography (HPLC) elution profile indicated themetabolites of daidzein and genistein by strain AUH-JLR41and strain AUH-JLR23wereexactly the same as that of the authentic DHD and DHG. Mass spectrometry (ESI-MS)analysis indicated that the molecular weight of the metabolite of daidzein by strainAUH-JLR41was256, which was the same as that of the authentic DHD. Similarly, themolecular weight of the metabolite of genistein was272, which was the same as that of theauthentic DHG. Therefore, the metabolites of daidzein and genistein by bacterial strainsAUH-JLR41and strain AUH-JLR23were identified as DHD and DHG, respectively.The enantiomeric excess (e.e.%) of the metabolites of daidzein and genistein by strainAUH-JLR41and strain AUH-JLR23was zero. In addition, the biotransforming kinetics and the bioconverting capacity of strain AUH-JLR41and strain AUH-JLR23wereinvestigated as well.