TABLE 2

Electron balances based on each metabolite’s electron equivalenceb

Substrate, product, or parameterMean ± SD for culture with pH on substratec
pH 6.0pH 6.5pH 6.9
GluFruCelloGluFruCelloGluFruCello
Substrate13.29 ± 0.913.59 ± 0.726.18 ± 3.513.10 ± 1.711.94 ± 0.924.31 ± 1.312.21 ± 0.511.83 ± 0.419.95 ± 1.1
Products
    Lactate7.37 ± 1.38.24 ± 0.77.46 ± 0.90.00 ± 0.00.08 ± 0.11.61 ± 0.30.00 ± 0.00.00 ± 0.00.01 ± 0.0
    Acetate1.14 ± 0.21.10 ± 0.10.98 ± 0.12.80 ± 0.32.94 ± 0.22.14 ± 1.23.09 ± 0.23.27 ± 0.15.08 ± 0.2
    Propionate0.24 ± 0.00.28 ± 0.10.29 ± 0.14.32 ± 0.74.39 ± 0.52.40 ± 3.64.10 ± 0.54.26 ± 0.17.60 ± 0.2
    Butyrate0.48 ± 0.00.50 ± 0.10.43 ± 0.00.53 ± 0.10.60 ± 0.00.52 ± 0.10.61 ± 0.00.61 ± 0.00.75 ± 0.0
    Formate0.02 ± 0.00.10 ± 0.00.18 ± 0.00.03 ± 0.10.01 ± 0.00.10 ± 0.10.06 ± 0.00.01 ± 0.00.00 ± 0.0
    Isobutyrate0.03 ± 0.00.05 ± 0.00.03 ± 0.00.61 ± 0.90.18 ± 0.20.98 ± 0.40.10 ± 0.00.08 ± 0.00.12 ± 0.0
    Valerate0.08 ± 0.00.16 ± 0.00.22 ± 0.10.10 ± 0.00.18 ± 0.00.16 ± 0.10.20 ± 0.10.20 ± 0.00.16 ± 0.1
    Isovalerate0.04 ± 0.00.09 ± 0.00.25 ± 0.20.00 ± 0.00.06 ± 0.00.43 ± 0.30.00 ± 0.00.12 ± 0.10.09 ± 0.0
    Citrate0.40 ± 0.30.64 ± 0.41.42 ± 0.50.00 ± 0.00.02 ± 0.02.97 ± 1.90.00 ± 0.00.00 ± 0.00.01 ± 0.0
    Hydrogen0.08 ± 0.00.15 ± 0.00.02 ± 0.00.29 ± 0.00.15 ± 0.00.28 ± 0.40.13 ± 0.00.04 ± 0.00.04 ± 0.0
    Ethanol0.21 ± 0.00.21 ± 0.00.29 ± 0.00.68 ± 0.20.62 ± 0.00.67 ± 0.20.77 ± 0.20.69 ± 0.11.34 ± 0.1
    Biomass0.89 ± 0.10.76 ± 0.21.15 ± 0.31.22 ± 0.31.09 ± 0.21.86 ± 0.60.74 ± 0.31.07 ± 0.11.55 ± 0.7
RSa0.00 ± 0.00.00 ± 0.013.21 ± 3.70.00 ± 0.00.00 ± 0.05.36 ± 4.60.00 ± 0.00.00 ± 0.00.00 ± 0.0
Total10.76 ± 1.112.06 ± 0.925.63 ± 3.49.91 ± 0.99.69 ± 0.518.82 ± 1.08.65 ± 0.69.67 ± 0.4315.42 ± 0.6
% recovery80.90 ± 4.4288.78 ± 5.297.96 ± 0.775.85 ± 3.281.22 ± 1.677.41 ± 0.773.12 ± 6.181.69 ± 3.0777.38 ± 4.2
  • a RS, remaining substrate at end of experiment.

  • b Electrons for the biomass were determined based on the measured chemical oxygen demand. % recovery was calculated based on how much of the initial electron equivalents could be tracked by measurements at the end of the experiment.

  • c Glu, Fru, and Cello indicate that the initial substrate was glucose, fructose, or cellobiose, respectively. All concentrations and electron equivalents are those measured at the end of the experiment.