TABLE 3.
Growth of and isovaleric acid production by two strains of P. freudenreichii in two culture media with or without 20 mM α-KG added
| Medium | Strain | α-KG | Growth
|
Isovaleric acid concn (μM)a
|
||
|---|---|---|---|---|---|---|
| Generation time (h) | Maximal dry wt (g/liter) | Maximal growthb | End of incubationc | |||
| YEL | TL 34 | − | 4.8 ± 0.06 | 1.2 | 40 | 116 ± 4.4 |
| + | 4.3 ± 0.06 | 1.2 | 38 | 216 ± 4.5 | ||
| ITGP23 | − | 8.8 ± 0.80 | 1.1 | 20 | 72 ± 5.4 | |
| + | 7.4 ± 0.51 | 1.1 | 22 | 130 ± 1.9 | ||
| YEL-Sd | TL 34 | − | 13.2 ± 0.65 | 0.9 | 102 ± 7 | 150 ± 29.2 |
| + | >100 | NDe | ND | ND | ||
| ITGP23 | − | 15.3 ± 0.71 | 0.8 | 61 ± 1 | 129 ± 27.0 | |
| + | >100 | ND | ND | ND | ||
The isovaleric acid concentration is the sum of the 2- and 3-methylbutyric acids concentrations. The values are means ± standard deviations based on the results obtained for different culture tubes incubated at the same time (n = 3 or 4).
Maximal growth in YEL and YEL-S media occurred at 48 h and 6 days, respectively.
The end of incubation in YEL and YEL-S media occurred at 120 h and 15 days, respectively.
YEL-S medium was YEL medium that was modified by lowering the pH to 5.4 (compared to pH 6.8 in YEL medium) and adding 2.1% NaCl; YEL-S medium was incubated at 24°C, whereas YEL medium was incubated at 30°C.
ND, not determined.