C-ring cleavage of isoflavone daidzein by a newly-isolated facultative Enterococcus hirae AUH-HM195 from crossoptilon mantchuricum feces?
兼性肠球菌Enterococcus hirae AUH-HM195对黄豆苷原的开环转化

Abstract: Objective] To isolate specific bacteria capable of biotransforming isoflavone daidzein. Methods] Fresh crossoptilon mantchuricum feces was diluted serially from 10-1 to 10-8 in Brain Heart Infusion (BHI)liquid medium in the anaerobic chamber at 37?C. Single colony was isolated and incubated in BHI liquid medium containing 0.1mmol/L daidzein under anaerobic conditions. The culture medium was detected by HPLC method after being incubated for 3 days. Results] A gram-positive facultative anaerobic bacterium designated strain AUH-HM195 capable of cleaving the C-ring of isoflavone daidzein was isolated. Basic Local Alignment Search Tool (BLAST) search on the GenBank revealed that the full-length of 16S rDNA gene sequence for strain AUH-HM195 has 100% similarity to that of Enterococcus hirae (DSM20160). Based on HPLC retention time, UV spectrum, 1H and 13C NMR analysis, the metabolite of daidzein by strain Enterococcus hirae AUH-HM195 was identified as O-desmethylangolensin. Two peaks were observed when purified O-desmethylangolensin was eluted on a chiral column. The enantiomeric excess (% e.e.) of O-desmethylangolensin was 66.9%. Conclusion] Bacterial strain Enterococcus hirae AUH-HM195 is the first reported Enterococcus bacterium with C-ring cleavage activity. It is also the first reported facultative bacterium capable of metabolizing isoflavones.