TABLE 2.
Effect of ethanol on P(3HB) molecular weight produced by E. coli JM109 expressing PhaRCYB-4 (pBBR1-phaRCYB-4AB) and PhaRCBm (pGEM-phaRCBmAB) in two-stage culturea
| Expressed synthaseb | Culture conditionsc |
Time of harvest (h) | Cell dry wt (g/liter) | P(3HB) content (wt%) | Mol wt |
Relative chain no. | ||
|---|---|---|---|---|---|---|---|---|
| First stage (0–24 h) | Second stage (24–72 h) | Mn (103) | Mw/Mn | |||||
| PhaRCYB-4 | LB + glucose | 24 | 3.3 ± 0.0 | 27 ± 0 | 1,250 ± 106 | 1.6 | 1.0 | |
| LB + glucose | M9 | 72 | 2.7 ± 0.0 | 31 ± 2 | 1,140 ± 61 | 2.8 | 1.0 | |
| LB + glucose | M9 + ethanol | 72 | 3.0 ± 0.0 | 36 ± 4 | 42 ± 2 | 11.1 | 36.1 | |
| PhaRCBm | LB + glucose | 24 | 4.2 ± 0.0 | 23 ± 1 | 1,050 ± 68 | 1.9 | 1.0 | |
| LB + glucose | M9 | 72 | 3.0 ± 0.0 | 33 ± 1 | 1,060 ± 72 | 2.0 | 1.0 | |
| LB + glucose | M9 + ethanol | 72 | 3.0 ± 0.0 | 35 ± 3 | 270 ± 28 | 4.8 | 4.2 | |
a
Results are means ± standard deviations from three separate experiments.
b
pBBR1-phaRCYB-4AB and pGEM-phaRCBmAB are low- and high-copy-number plasmids, respectively.
c
Cells were cultured in LB medium containing glucose (20 g/liter) for 24 h at 37°C and then incubated in glucose-free M9 medium with or without supplementation of ethanol (4 g/liter) for a further 48 h at 37°C.