1515 hplc system

Cell optical density (OD) was measured at 600 nm with TU-1810 spectrophotometer. Residual glucose and xylose were quantified by Waters 1515 HPLC system, equipped with a Bio-Rad HPX-87H column and a refractive index detector (Waters 2414, Milford, USA). Isocratic elution through the column was conducted using 5 mM of sulfuric acid at 0.6 mL/min and 65 °C.
Quantification of tyrosol and icariside D2 was carried out using Agilent 1200 HPLC system equipped with a C18 column (150 * 4.6 mm with a particle size of 5 μm, Bonna-Agela, China) and a PDA detector (Agilent). After fermentation, the broth samples were centrifuged, and 10 μL of cell-free supernatants was filtered through 0.22 μm pore-sized syringe filter before being measured under room temperature with a mobile phase (20% methanol, 80% water, and 0.1% acetate) at 1 mL/min. The tyrosol and icariside D2 were measured at 225 nm. The structure of icariside D2 was further analyzed using high-resolution LC–MS/MS [Synapt G2-Si Q-TOF mass spectrometer coupled with an ACQUITY UPLC system (Waters, USA)] under positive-ion mode. All of the HPLC analysis were quantified using a five-point calibration curve and the R² coefficient for the calibration curve was higher than 0.99.

Cell growth was monitored by measuring the absorbance at 600 nm (OD₆₀₀) using an UV–VIS spectrophotometer. Glucose consumption was quantified by a biosensor SBA-90 (Biology Institute of Shandong Academy of Sciences, China). Residual concentration of xylose was measured using Waters 1515 HPLC system, equipped with a Bio-Rad HPX-87H column and a refractive index detector (Waters 2414, Milford, USA), and the column was eluted at 65 °C with 5 mM sulfuric acid at 0.6 mL/min.
The broth samples were centrifuged, and supernatants were filtered through 0.22 μm syringe filter, and injected to the HPLC system. 4-HMA and l-tyrosine were measured using Agilent 1200 HPLC system equipped with a C18 column (250 × 4.6 mm, Agilent) and a PDA detector (Agilent) at 196 nm with a mobile phase (10 % methanol-90 % H₂O, addition of 0.1 % formic acid) at 1.0 mL/min. The structure of 4-HMA was identified using LC–MS (Agilent 1200 HPLC system and 6310 Ion Trap mass spectrum system, Agilent) under negative ion mode. All of the HPLC analysis were quantified using a six point standard curve and the R² coefficient for the standard curve was higher than 0.99.