对黄豆苷原具转化作用的耐氧突变株Aeroto-AUH-JLC140未知代谢产物分离、鉴定及抗氧化活性测定

【目的】与原出发菌株AUH-JLC140相比,耐氧突变株Aeroto-AUH-JLC140在其生长过程中产生一种未知物质,且该未知物质的产生与添加底物黄豆苷原无关。对该未知物质进行分离纯化和结构鉴定,并测定其产生动态及抗氧化活性。【方法】利用高效液相色谱对未知物质进行分离,经紫外吸收图谱、质谱、核磁共振氢谱和碳谱等分析,对未知物质进行结构鉴定;通过1,1-二苯基-2-苦味酰基自由基(DPPH)清除试验测定其抗氧化活性。【结果】Aeroto-AUH-JLC140产生的未知物质被鉴定为吲哚,接种后15 h菌株产吲哚最高,所产吲哚量为19.89 mg/L。浓度为0.2 mmol/L(即23.40 mg/L)的吲哚除对DPPH自由基具有明显清除作用外,还能有效降低脑心浸液(BHI)液体培养基的氧化-还原电位。【结论】耐氧突变株Aeroto-AUH-JLC140产生的未知代谢产物为吲哚,菌株通过产生吲哚降低培养基氧化-还原电位,进而为该菌株的生长提供适宜的低氧微环境。

Isolation, identification and anti-oxidative activity of metabolites from oxygen-tolerant mutant strain Aeroto-AUH-JLC140 capable of biotransforming daidzein

Objective] Compared to the original bacterium strain AUH-JLC140, its oxygen-tolerant mutant strain named Aeroto-AUH-JLC140 was able to produce an unknown substance. In addition, the production of the unknown substance was not associated with the addition of the substrate daidzein to the cultural medium. The objective of this study was to isolate and identify the unknown substance, and then to study the kinetics and the anti-oxidative capacity of the unknown substance produced by the oxygen-tolerant mutant strain Aeroto-AUH-JLC140. Methods] The unknown substance was isolated by high-performance liquid chromatography (HPLC) method. Based on the analyses of the UV spectrum, electrospray ionization mass spectrometry (ESI-MS) as well as the 1H and 13C nuclear magnetic resonance spectroscopy, the unknown substance was identified. The anti-oxidative activity of the unknown substance was determined by the 1,1-Diphenyl-2-Picrylhydrazyl (DPPH) scavenging activity. Results] The unknown substance produced by the oxygen-tolerant mutant strain Aeroto-AUH-JLC140 was identified as indole. Kinetics study showed that indole reached to the highest after being incubated for 15 h and the highest amount of indole in the cultural broth was 19.89 mg/L. Study on free radical-scavenging activity indicated that 0.2 mmol/L (i.e. 23.40 mg/L) of indole not only showed an obvious DPPH radical-scavenging activity but also decreased the oxidation-reduction potential (ORP) of brain heart infusion (BHI) liquid medium. Conclusion] The unknown metabolite produced by the oxygen-tolerant mutant strain Aeroto-AUH-JLC140 is indole. The amount of indole produced by strain Aeroto-AUH-JLC140 can decrease the ORP of BHI liquid medium, which subsequently provides a suitable microenvironment with lower ORP for growth of strain Aeroto-AUH-JLC140 in the presence of atmospheric oxygen.