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Table 3 Overview of critical performance parameters for the bioreactor with pertraction (BP; pH 6) and the bioreactor without pertraction (BNP; pH 7) for the different operating phases as defined in Table 1 (average ± stdev)

From: Upgrading syngas fermentation effluent using Clostridium kluyveri in a continuous fermentation

  Phase OLR (g COD L−1 day−1) OLR (mM-C day−1) n-Butyric acid (mM day−1) n-Caproic acid  (mM day−1) n-Caprylic acid (mM day−1) Specificity C6 (%) Specificity C8 (%) Carbon conversion efficiency  (%) Extr. C6 (%) Extr. C8 (%)
BP II–III 7.0 ± 0.4 151.9 ± 31.4 0.9 ± 0.7 8.4 ± 8.4 0.2 ± 0.1 88.5 ± 10.1 3.7 ± 2.9 38.9 ± 17.4 80.4 ± 10.5 100.0 ± 0.0
IV 10.9 ± 0.4 255.2 ± 7.4 1.3 ± 0.2 16.2 ± 5.4 0.6 ± 0.4 90.9 ± 2.0 3.9 ± 2.2 41.9 ± 2.5 64.8 ± 13.7 94.4 ± 6.6
 V 14.2 ± 1.0 298.3 ± 9.6 1.7 ± 0.4 19.1 ± 6.6 1.0 ± 0.4 87.7 ± 3.9 6.4 ± 3.0 38.5 ± 12.6 37.8 ± 27.2 65.0 ± 26.5
 VI 16.3 ± 0.4 370.0 ± 9.7 9.4 ± 0.7 39.9 ± 0.9 1.4 ± 0.2 83.0 ± 1.0 4.0 ± 0.4 79.9 ± 2.0 42.7 ± 6.9 77.0 ± 4.5
 VII 10.7 ± 3.3 244.6 ± 74.4 7.8 ± 0.11 23.1 ± 4.7 0.47 ± 0.3 79.5 ± 1.9 1.9 ± 1.6 76.4 ± 19.5 70.0 ± 40 101 ± 2.7
BNP  II 6.9 ± 0.2 122.5 ± 31.7 1.0 ± 0.3 11.1 ± 2.7 0.8 ± 0.2 86.5 ± 0.5 8.1 ± 0.2 65.9 ± 17.4   
 III–IV 10.9 ± 0.4 233.0 ± 7.9 1.7 ± 0.3 15.7 ± 0.5 1.2 ± 0.1 85.5 ± 1.2 8.5 ± 0.4 47.5 ± 2.5   
 V 11.3 ± 1.2 241.0 ± 28.4 1.5 ± 0.2 18.6 ± 2.9 1.8 ± 0.3 84.7 ± 1.5 10.8 ± 1.2 54.7 ± 6.5   
 VI 13.0 ± 0.03 296.5 ± 0.7 7.8 ± 0.7 37.6 ± 1.6 2.6 ± 0.01 81.4 ± 0.5 7.4 ± 0.3 93.6 ± 4.4   
 VII 12.3 ± 1.2 279.7 ± 27 5.7 ± 0.7 35.3 ± 2.7 2.14 ± 0.4 84.2 ± 1.0 6.7 ± 0.7 90.1 ± 0.7   
  1. COD chemical oxygen demand, C6 n-caproic acid, C8 n-caprylic acid, Extr. extraction efficiency
  2. Production rates for the three products (n-butyric, n-caproic and n-caprylic acid) are shown. Weighted averages were taken for the steady state periods (starting 3 HRTs after a change in condition), and for n ≥ 3