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Table 1 Summary of the experimental performances

From: Microbial insights of enhanced anaerobic conversion of syngas into volatile fatty acids by co-fermentation with carbohydrate-rich synthetic wastewater

 G5GS5G15GS15P5PS5P15PS15S
CO consumption (mL/day)57.4 ± 2.851.8 ± 2.526.1 ± 1.421.9 ± 2.345.6 ± 2.1
H2 consumption (mL/day)61.4 ± 3.248.2 ± 2.727.5 ± 2.221.1 ± 2.742.4 ± 2.8
CO conversion efficiency (%)a71.7 ± 3.564.7 ± 4.032.6 ± 1.827.3 ± 2.957.6 ± 2.8
H2 conversion efficiency (%)a76.7 ± 1.260.3 ± 0.934.4 ± 0.726.4 ± 2.153.0 ± 1.7
Acetate conversion efficiency from syngas (%)b90 ± 2 69 ± 1153 ± 3212 ± 596 ± 2
VFAs conversion efficiency from organic (%)c84 ± 192 ± 481 ± 284 ± 295 ± 393 ± 294 ± 493 ± 5
Glucose/BSA (mg/L)230 ± 19227 ± 291256 ± 1361194 ± 211725 ± 37794 ± 713584 ± 2033346 ± 309296 ± 19
Total COD (mg COD/L)d5300682215,90017,4227100862221,30022,8221522
VFAs/total COD (%)d82 ± 1.286 ± 2.375 ± 0.978 ± 2.582 ± 1.070 ± 2.164 ± 2.763 ± 3.255 ± 1.3
Residual syngas/total COD (%)d6 ± 0.54 ± 0.310 ± 0.85 ± 0.440 ± 1.2
Residual organic/total COD (%)d5 ± 0.23 ± 0.19 ± 0.48 ± 0.711 ± 1.410 ± 0.824 ± 1.922 ± 2.2
Unbalanced COD/total COD (%)d12 ± 2.54 ± 0.115 ± 2.211 ± 3.16 ± 0.59 ± 1.311 ± 1.610 ± 0.95 ± 1.3
NH4+-N (mg/L)80 ± 587 ± 1778 ± 480 ± 5935 ± 46916 ± 491608 ± 911623 ± 63 
  1. aThe P-values of CO/H2 conversion efficiency among all the reactors were calculated by Duncan analysis and shown in Additional file 1: Table S1
  2. bOne mole acetate was produced from 4 mol H2 or 4 mol CO (4CO + 2H2O → CH3COOH + 2CO2 and 4H2 + 2CO2 → CH3COOH + 2H2O), and the theoretical acetate production from H2 and CO was calculated according to the above two stoichiometric equations. The acetate conversion efficiency from converted CO and H2 was calculated: the measured acetate production/ the theoretical acetate production from H2 and CO
  3. cThe theoretical VFA production (mgCOD/L) from organic was calculated by subtracting the COD of residual organic from the COD of added organic. The VFAs conversion efficiency from organic was calculated: the measured VFAs production/the theoretical VFAs production from organic
  4. dCOD mass balance in all bottles at steady state. Total COD was the sum of organic and syngas. COD was calculated based on the following: CO: 0.57 gCOD/g, H2: 8 gCOD/g, ACETATE: 1.07 gCOD/g, propionate: 1.51 gCOD/g, butyrate: 1.81 g COD/g, valerate: 2.04 g COD/g, carbohydrate: 1.06 g COD/g, protein: 1.42 g COD/g, lactate: 1.06 gCOD/g. Unbalanced COD was calculated by subtracting the COD of VFAs, residual syngas, residual organic from total COD