Table 1. Cultivation parameters of S. meliloti 2011 grown in the chemostat at extracellular pH 7.0 and pH 6.1.
| Cultivation parameters | Chemostat pH 7.0 | Chemostat pH 6.1 |
|---|---|---|
| Dilution rate (h−1) | 0.073 ± 0.002 | 0.070 ± 0.003 |
| Optical Density(600nm) | 4.57 ± 0.02 | 1.82 ± 0.12 |
| Bacterial cell number (cells.ml−1)a | 4.70 × 109 ± 0.9 × 109 | 1.79 × 109 ± 1 × 109 |
| Culturable cells/total bacteria (%) (c.f.u. × 100 total bacteria−1)b | 100% | 26% |
| Dry weight (mg.ml−1) | 1.66 ± 0.11 | 0.78 ± 0.05 (0.20 g of these being able to grow)b |
| Cells/Dry weight (cells.mg−1) | 2.8 × 109 ± 0.6 × 109 | 2.3 × 109 ± 1.3 × 109 |
| Dry weight/cell (pg.cell−1) | 0.35 ± 0.02 | 0.43 ± 0.02 |
| EPS production (mg.mg dry weight−1) | 0.04 ± 0.22 | 0.24 ± 0.06 |
| PHB content (% w.w−1) | 6.8 ± 0.12 | 5.3 ± 0.04 |
| Glucose consumption (g.l−1) | 3.04 ± 0.15 | 1.46 ± 0.08 |
| Ammonia (limiting nutrient at pH 7.0) (mM) | ND | 6.9 |
| rCO2 (mmol.l−1.h−1) | 3.58 ± 0.07 | 1.66 ± 0.01 |
 (mmol.C-mol−1 h−1) |
56 ± 2 | 55 ± 2 |
| CO2 production/culturable cells (fmol.cfu−1.h−1) | 0.76 ± 0.01 | 3.56 ± 0.06 [↑ ca. 4.7 times] |
| rO2 (mmol.l−1.h−1) | 3.97 ± 0.1 | 2.19 ± 0.1 |
 (mmol.C-mol−1 h−1) |
62 ± 1 | 72 ± 1 |
| O2 consumption/culturable cells (fmol.cfu−1.h−1) | 0.8 ± 0.01 | 4.7 ± 0.2 [↑ ca. 5.8 times] |
| RQ (rCO2.rO2−1) | 0.9 ± 0.04 | 0.76 ± 0.04 |
| YX/S (C-mol.C-mol−1) | 0.64 ± 0.04 | 0.62 ± 0.06 |
 (mol.C-mol−1) |
0.48 ± 0.01 | 0.49 ± 0.01 |
| YEPS/S (YP/S estimation) (C-mol.C-mol−1) | 0.02 ± 0.01 | 0.13 ± 0.03 |
C balance ( + YX/S + YEPS/S) |
1.14 ± 0.01 | 1.24 ± 0.1 |
All values are expressed with their corresponding standard deviations.
rO2: rate of O2 consumption (mmol.l−1.h−1).
qO2/X: mmol O2 consumption/C-mol of biomass/h.
rCO2: rate of CO2 production (mmol.l−1.h−1).
qCO2/X: mmol of CO2 production/C-mol of biomass/h.
Yx/s: biomass-growth yield (C-mol of biomass produced/C-mol of consumed glucose).
YCO2/S: CO2 production (molCO2/C-mol of consumed glucose).
YEPS/S: exopolysaccharide production (C-mol EPS/C-mol of consumed glucose).
RQ: Respiratory Quotient.
ND: Non-detected.
aNumber of bacteria counted in Petroff-Hausser chamber.
bProportion of bacteria counted by plating with respect to those counted in the Petroff-Hausser chamber (%).