Table 2.
Effect of buffer and starting culture pH on BC yields.
| Buffer | Ionic Strength (mM) | Actual starting pH | Final pH (9th day) | Change of pH (9th day) | BC yield (g/L) |
|---|---|---|---|---|---|
| Acetate | 242 | 4.66 | 4.50* | -0.16 | - |
| 230 | 5.05 | 4.95 | -0.10 | - | |
| 214 | 5.47 | 5.34* | -0.13 | - | |
| 206 | 5.90 | 5.62** | -0.28 | - | |
| Phosphate | 90 | 5.00 | 3.89** | -1.11 | 4.63±0.06a |
| 600 | 4.76 | 4.32** | -0.44 | - | |
| 600 | 5.03 | 4.45** | -0.58 | - | |
| 600 | 5.49 | 4.91** | -0.58 | - | |
| 600 | 5.86 | 5.26** | -0.60 | - | |
| Citrate | 600 | 4.63 | 4.70* | 0.07 | - |
| 600 | 4.99 | 4.99 | 0 | - | |
| 600 | 5.29 | 5.47* | 0.18 | - | |
| 600 | 5.67 | 5.75* | 0.08 | - | |
| Phthalate | 61 | 4.84 | 3.94** | -0.90 | 2.88±0.04e |
| 73 | 5.18 | 4.31** | -0.87 | 5.06±0.18a | |
| 84 | 5.59 | 4.86** | -0.73 | 4.66±0.03a | |
| 92 | 6.02 | 4.98** | -1.04 | 4.14±0.05b,c | |
| Control group | － | 4.68 | 3.16** | -1.52 | 3.98±0.08c,d |
| － | 5.08 | 3.28** | -1.80 | 4.27±0.07b | |
| － | 5.46 | 3.32** | -2.14 | 4.03±0.09c | |
| － | 5.83 | 3.35** | -2.48 | 3.75±0.12d |
Change of pH= Final pH-Actual starting pH
(-) Indicates no obvious BC production
Significance analysis for actual starting pH and final pH; (*) and (**) denote statistically significant changes (LSD t-test, p value ≤ 0.05 and p value ≤ 0.01 respectively)
BC yield is presented as the mean ± SD for triplicate measurements. Means with different superscripts in the same column are considered statistically different (LSD t-test, p value ≤ 0.05)