Abstract: The substrate tectorigenin was prepared by acid hydrolysis of the crude extract of Belamcanda chinensis. In this study,it was found that oxygen-tolerant bacterial mutant Aeroto-Niu-O16 was able to transform tectorigenin in the presence of atmospheric oxygen.The metabolite of tectorigenin generated by strain Aeroto-Niu-O16 was identified as dihydrotectorigenin based on the MS spectrometry, ¹H and ¹³C nuclear magnetic resonance (NMR) analyses.The optimal bioconverting period was 36~48 h.The maximal concentration of tectorigenin that strain Aeroto-Niu-O16 was able to transform effectively was 0.8 mmol/L and the average bioconverting rate was 41.2%.Furthermore,when 0.15% (m/v) of L-cysteine was added in the cultural medium,the average bioconverting rate of the substrate tectorigenin was increased from 41.2% to 50.7%.We here showed for the first time that tectorigenin was able to be converted to dihydrotectorigenin through microbial biotransformation method.Our study provided the possibility of biosynthesizing dihydrotectorigenin in the future.

Key words: Belamcanda chinensis, tectorigenin, dihydrotectorigenin, oxygen-tolerant bacterium, microbial biotransformation