Table 1.
Concentration of compounds and calculated parameters on the steady state of aerated (at 0.02 vvm) or non-aerated S. cerevisiae continuous cultures, fed with sterilized (SM) or non-sterilized medium (NSM)
| Compound (g L−1) | Aeration and dilution rates (D) | |||
|---|---|---|---|---|
| 0 vvm and 0.08 h−1 | 0.02 vvm and 0.08 h−1 | |||
| SM | NSM | SM | NSM | |
| A (Non-supplemented with yeast extract) | ||||
| Biomass | 5.90 ± 0.21 | 4.93 ± 0.42 | 7.33 ± 0.29 | 6.83 ± 0.72 |
| Ethanol | 38.25 ± 0.84 | 37.48 ± 1.61 | 41.87 ± 0.62 | 39.97 ± 0.04 |
| R sugars | 14.46 ± 0.52 | 26.52 ± 0.33 | 4.73 ± 0.57 | 12.18 ± 1.63 |
| Fructose | 4.27 ± 1.23 | 26.27 ± 3.35 | 9.56 ± 2.33 | 10.76 ± 1.16 |
| Glucose | 2.17 ± 0.37 | 0.90 ± 0.14 | 2.62 ± 0.10 | 0.39 ± 0.01 |
| Succinic acid | 0.16 ± 0.01 | 0.06 ± 0.08 | 0.21 ± 0.09 | 0.12 ± 0.00 |
| Glycerol | 4.48 ± 0.38 | 3.08 ± 0.23 | 7.00 ± 0.11 | 4.44 ± 0.14 |
| Diacetyl | nd | nd | nd | nd |
| Acetic acid | nd | nd | nd | nd |
| Acetoin | 0.33 ± 0.12 | nd | nd | 0.18 ± 0.03 |
| NH4 + | 1.80 ± 0.22 | 1.55 ± 0.17 | 1.17 ± 0.09 | 0.89 ± 0.05 |
| YX/S | 0.069 ± 0.002 | 0.067 ± 0.005 | 0.077 ± 0.003 | 0.078 ± 0.007 |
| YP/S | 0.447 ± 0.007 | 0.510 ± 0.020 | 0.439 ± 0.004 | 0.455 ± 0.008 |
| PP | 3.060 ± 0.067 | 2.998 ± 0.129 | 3.350 ± 0.050 | 3.198 ± 0.003 |
| pH | 3.0 ± 0.1 | 2.9 ± 0.3 | 2.8 ± 0.1 | 2.7 ± 0.3 |
| Compound (g L−1) | Aeration and dilution rates (D) | |||
|---|---|---|---|---|
| 0 vvm and 0.10 h−1 | 0.02 vvm and 0.12 h−1 | |||
| SM | NSM | SM | NSM | |
| B (Supplemented with yeast extract)a | ||||
| Biomass | 6.57 ± 0.68 | 6.42 ± 0.23 | 8.16 ± 0.70 | 8.28 ± 0.90 |
| Ethanol | 42.95 ± 2.86 | 46.22 ± 3.20 | 45.11 ± 0.49 | 46.92 ± 1.87 |
| R sugars | 5.86 ± 0.48 | 6.60 ± 0.25 | 7.53 ± 0.89 | 7.23 ± 0.09 |
| Fructose | 3.56 ± 0.19 | 5.03 ± 0.32 | 2.91 ± 0.55 | 6.63 ± 0.04 |
| Glucose | 0.06 ± 0.04 | 0.41 ± 0.19 | nd | 0.57 ± 0.00 |
| Succinic acid | 0.08 ± 0.06 | 0.14 ± 0.02 | 0.08 ± 0.06 | 0.12 ± 0.04 |
| Glycerol | 2.76 ± 0.17 | 3.93 ± 0.17 | 3.00 ± 0.08 | 3.14 ± 0.06 |
| Diacetyl | nd | nd | nd | nd |
| Acetic acid | nd | nd | nd | nd |
| Acetoin | nd | nd | nd | nd |
| NH4 + | 1.16 ± 0.12 | 1.59 ± 0.51 | 0.94 ± 0.05 | 0.77 ± 0.13 |
| YX/S | 0.070 ± 0.007 | 0.069 ± 0.002 | 0.088 ± 0.007 | 0.089 ± 0.010 |
| YP/S | 0.456 ± 0.028 | 0.495 ± 0.033 | 0.488 ± 0.001 | 0.506 ± 0.020 |
| PP | 4.295 ± 0.286 | 4.622 ± 0.320 | 5.413 ± 0.059 | 5.630 ± 0.224 |
| pH | 2.8 ± 0.3 | 2.7 ± 0.1 | 2.6 ± 0.2 | 2.6 ± 0.3 |
Medium contained agave juice (adjusted at 100 g L−1 of R sugars), ammonium sulfate (1 g L−1) and ammonium phosphate monobasic (4 g L−1). YX/S is biomass yield (g g−1). YP/S is ethanol yield (g g−1). PP is ethanol productivity [g (Lh)−1]. Values are the means ± standard deviations (n = 3)
R sugars are Reducing sugars, nd compound not detected under the analysis conditions
aExperiments using media supplemented with yeast extract were performed at higher D, because this supplementation allowed this increase without losing stability in the continuous culture