TABLE 3.
pH | Ysx | CO2/ethanol ratio | qs | qCO2 | qethanol | qglycerol | qpyruvate | qacetate | qlactate | C recovery (%) |
---|---|---|---|---|---|---|---|---|---|---|
2.5 | 0.067 | 0.97 | 4.56 | 8.0 | 8.2 | 0.55 | <0.01 | <0.01 | <0.01 | 103.3 |
3.0 | 0.078 | 1.01 | 3.92 | 6.7 | 6.7 | 0.54 | <0.01 | 0.02 | 0.08 | 102.7 |
3.5 | 0.075 | 1.03 | 4.10 | 7.2 | 7.0 | 0.61 | <0.01 | 0.02 | 0.07 | 103.8 |
4.0 | 0.071 | 1.03 | 4.32 | 7.6 | 7.3 | 0.64 | <0.01 | 0.03 | 0.08 | 103.1 |
4.5 | 0.082 | 1.02 | 3.74 | 6.3 | 6.2 | 0.61 | <0.01 | 0.02 | 0.09 | 103.1 |
5.0 | 0.085 | 1.00 | 3.59 | 5.9 | 6.0 | 0.59 | <0.01 | 0.02 | 0.10 | 102.7 |
Avg | 0.076 | 1.01 | 4.04 | 7.0 | 6.9 | 0.59 | <0.01 | 0.02 | 0.07 | 103.1 |
Specific rates of substrate consumption (qs) and metabolite production (q) are presented as millimoles per gram of biomass per hour. The CO2 to-ethanol ratio equals the quotient of the specific rates of production of these metabolites. The biomass yield on a substrate (Ysx) is given as grams of biomass per gram of substrate utilized (i.e., the reservoir substrate concentration minus the residual concentration in the culture). Data were calculated as described in Materials and Methods and are the result of one cultivation at each pH.