Screening and preliminary study on one endophytic bacterium of Rhodiola crenulata

Abstract:

[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.