一株红景天内生细菌的筛选及初步研究

【目的】从红景天根部筛选并鉴定一株产酪醇的细菌，初步研究其产酪醇特性，为寻找红景天替代资源提供新途径。【方法】用NA培养基从大花红景天根部中分离内生细菌，通过薄层层析(TLC)、高效液相色谱(HPLC)、气相色谱-质谱联用(GC-MS)筛选出产量最大的菌株，经菌落形态分析、革兰氏染色分析及16S rRNA基因序列分析其分类学地位。单因素实验确定初始pH、培养温度、发酵时间及接种量对菌株产酪醇活力的影响。【结果】从大花红景天根部分离出14株内生细菌，其中8株能产酪醇，筛选出酪醇产量最大的菌株B3，经菌落形态分析、革兰氏染色分析及16S rRNA基因序列分析初步鉴定为水生拉恩氏菌(Rahnella aquatilis)。研究其发酵条件，其最适pH为6.0，最适温度为32 °C，最佳发酵时间为42 h，最佳接种量为15%。在最适发酵条件下，用改良NA培养基发酵，B3菌株酪醇的产量为15.68 mg/L。【结论】B3菌株是一株具有产酪醇能力的细菌，在最适发酵条件下酪醇产量达到15.68 mg/L，具有潜在的开发价值。

Screening and preliminary study on one endophytic bacterium of Rhodiola crenulata

Objective] To research the alternative resources of Rhodiola crenulata, a tyrosol-producing strain was isolated and identified from the root of Rhodiola crenulata. The production features of the strain were preliminary studied. Methods] Endophytic bacteria were isolated from Rhodiola crenulata with NA medium. The best potential strain to produce tyrosol was selected through thin-layer chromatography (TLC), high performance liquid chromatography (HPLC), gas chromatography-mass spectrometry (GC-MS), followed by identification by colony morphology, gram staining analysis and 16S rRNA gene sequence profiles. Single factor experiments based on initial pH, culture temperature, incubation time and inoculum size were performed to optimize the conditions for tyrosol-production. Results] In this study, a total of 14 strains of endophytic bacteria were isolated from the root of Rhodiola crenulata. The best potential strain B3 was selected from 8 strains which can produce tyrosol. B3 strain was preliminary identification to Rahnella aquatilis by colony morphology, gram staining analysis and 16S rRNA gene sequence analysis. Researching its fermentation conditions, we found out that the optimum pH was 6.0, optimum temperature was 32 °C, the best fermentation time was 42 h, the best inoculation amount was 15%, and at the best fermentation conditions, the yield of tyrosol can reach 15.68 mg/L with improved NA culture medium. Conclusion] B3 strain is able to produce tyrosol, and the yield can reach to 15.68 mg/L at the optimal fermentation condition. The tyrosol-producing strain is expected to be explored its marketing values.