The biomass production of JW15 was determined by measuring the dry cell weights [20 (link)]. An aliquot (10 ml) of the culture broth was transferred to pre-weighed plastic conical tubes and centrifuged (5,000 ×g, 10 min, 4°C). The cell-free supernatant was separated to determine the concentration of organic acids. Pellets were washed thrice with ice-cold distilled water, dried at 80°C and left in a vacuum oven to obtain a constant weight.
The lactic and acetic acid production of JW15 was assessed using HPLC analysis, as described previously [16 (link)]. The obtained supernatant was passed through a 0.22-μm membrane filter and used for the HPLC analysis. Analysis was conducted using an Agilent 1100 apparatus (Agilent Technologies, USA), which comprises a column oven, auto-sampler, UV detector, and Aminex HPX-87H column (300 mm × 7.8 mm, 5 μm) (Bio-Rad, USA). The injection volume was 20 μl. Isocratic elution was performed using a 5 mM H2SO4 aqueous solution at 50°C. The flow rate was 0.6 ml/min. The chromatogram were detected at 210 nm using a UV detector. The concentration of each organic acid was evaluated from the external regression curve, which was constructed using standard mixtures at five concentrations.
The lactic and acetic acid production of JW15 was assessed using HPLC analysis, as described previously [16 (link)]. The obtained supernatant was passed through a 0.22-μm membrane filter and used for the HPLC analysis. Analysis was conducted using an Agilent 1100 apparatus (Agilent Technologies, USA), which comprises a column oven, auto-sampler, UV detector, and Aminex HPX-87H column (300 mm × 7.8 mm, 5 μm) (Bio-Rad, USA). The injection volume was 20 μl. Isocratic elution was performed using a 5 mM H2SO4 aqueous solution at 50°C. The flow rate was 0.6 ml/min. The chromatogram were detected at 210 nm using a UV detector. The concentration of each organic acid was evaluated from the external regression curve, which was constructed using standard mixtures at five concentrations.
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