Ultraspec 2000

Cell growth was recorded as optical density (OD) at 600_nm (Ultraspec 2000, Hitachi, Tokio, Japan). Cell dry weight was determined gravimetrically after collection of 10 mL culture broth (10 min, 4 °C, 8.000×g) in pre-weighed tubes, including a washing step with distilled water, and drying of the obtained pellet at 100 °C until constant weight. The ammonium concentration in cultivation supernatant was measured by a photometric test (LCK 303 kit, Hach Lange, Danaher, Washington, DC, USA). The concentration of glycerol and organic acids (succinate, formate, malate, citrate) in cultivation supernatant was analyzed by HPLC (Agilent 1260, Agilent, Krefeld, Germany), equipped with an 8 mm Rezex ROA-organic acid H column (Phenomenex, Torrance, CA, USA), operated with 0.013 N H₂SO₄ as mobile phase at 0.5 mL min⁻¹ and 65 °C and detection using a refractive index detector (Agilent, Santa Clara, CA, USA).

Cell growth was recorded as optical density (OD) at 600_nm (Ultraspec 2000, Hitachi, Japan). The cell dry weight was determined gravimetrically after collection of 10 mL culture broth for 10 min at 4°C and 9,000 × g (Eppendorf 5810 R, Hamburg, Germany) in pre-weighed tubes, including a washing step with distilled water, and drying of the obtained pellet at 100°C until constant weight. The ammonium concentration in cell-free supernatant was measured by a photometric test (LCK 303 kit, Hach Lange, Danaher, USA).