2.3. Fermentation profiles
Cell growth was monitored at 600 nm using a spectrophotometer (OD600). The concentrations of substrates and metabolites were determined by high-performance liquid chromatography (Agilent Technologies 1260 Series, Santa Clara, CA, USA) equipped with a refractive index detector using a Rezex ROA-Organic Acid H+ (8%) column (Phenomenex, Inc., Torrance, CA, USA). The column was eluted with 0.005 N H2SO4 at a flow rate of 0.6 mL/min and 50°C.