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Table 1 Effect of different pH regulation methods on cell growth and butanol production by C. acetobutylicum

From: A comparison of three pH control methods for revealing effects of undissociated butyric acid on specific butanol production rate in batch fermentation of Clostridium acetobutylicum

pH control NaOH neutralization CaCO 3 supplementation NaOAc buffering (pH)
  12 h 24 h 36 h 2 g/L 5 g/L 8 g/L 4.6 5.0 5.6
pH at 24 ha 4.7 ± 0.0 3.6 ± 0.0 3.6 ± 0.0 4.4 ± 0.0 4.7 ± 0.0 5.3 ± 0.0 4.1 ± 0.0 4.4 ± 0.0 5.0 ± 0.0
Cbutanol b 11.9 ± 0.7 3.8 ± 0.0 4.9 ± 0.1 8.8 ± 0.4 10.8 ± 0.1 7.9 ± 0.4 6.5 ± 0.3 12.3 ± 0.9 8.3 ± 0.4
Cbutyric acid c 4.3 ± 0.3 1.8 ± 0.2 1.7 ± 0.1 4.0 ± 0.3 5.4 ± 0.5 6.2 ± 0.2 2 ± 0.3 2.7 ± 0.5 4.0 ± 0.2
Biomass 0.69 ± 0.03 0.45 ± 0.06 0.39 ± 0.02 0.45 ± 0.05 0.41 ± 0.02 0.53 ± 0.01 0.51 ± 0.03 0.63 ± 0.02 0.70 ± 0.04
CUBA d 2.18 ± 0.14 1.0 ± 0.08 1.6 ± 0.09 2.68 ± 0.18 3.01 ± 0.26 1.50 ± 0.05 1.70 ± 0.28 1.92 ± 0.32 1.32 ± 0.07
qp 0.41 ± 0.02 0.22 ± 0.09 0.42 ± 0.02 0.49 ± 0.06 0.52 ± 0.01 0.25 ± 0.02 0.44 ± 0.01 0.58 ± 0.01 0.36 ± 0.02
  1. a pH at 24 h: pH values at 24 h of fermentation. b Cbutanol (g/L): Final butanol concentration at 72 h. Biomass (g/L): Cell biomass at 24 h. c Cbutyric acid: Butyric acid concentration at 24 h (peak concentration). CUBA (g/L): Concentration of undissociated butyric acid at 24 h.
  2. qp: Specific butanol production rates (between 24 and 36 h, h−1) were calculated based on the following equation: qp = (Cbutanol,36h − Cbutanol,24h)/(12 × Xcell biomass,24h).