Table 2.
Inhibition halos (mm) of the E. coli strains after treatment with different papain concentrations mixed with hydrogen peroxide. Aliquots (100 μL) of exponentially growing cultures of E. coli were mixed with 3 mL top agar (44–46°C) and spread on LB plates supplemented with antibiotic (ampicillin or chloramphenicol, according to the strain resistance). After 15 minutes, paper discs (5 mm diameter) containing different amounts of the papain (100 or 500 μg/disc) mixed or not with H2O2 (300 μg/disc) were placed in the center of the plates. After 24-hour incubation at 37°C the inhibition halos around the disc were measured. Values are the mean of 3 independent experiments with standard deviations not exceeding 15% (mean ± SD). 5% significance level was adopted to compare data.
| Growth inhibition halos (mm) of E. coli strains | ||||||
|---|---|---|---|---|---|---|
| Agents (10 μL/disc) | IC203 | IC204 | IC205 | IC206 | IC207 | WP2 (WT) |
| uvrA oxyR | uvrA umuDC | uvrA umuDC mutM | uvrA umuDC mutY | uvrA umuDC mutM oxyR | ||
| H2O2 (300 μg) | 48.0 ± 1.4 | 30.5 ± 2.7 | 20.0 ± 2.4 | 17.0 ± 2.3 | 37.7 ± 1.0 | 16.0 ± 0.5 |
| Papain (100 μg) plus H2O2 (300 μg) | 45.0 ± 0.1* | 22.0 ± 1.8* | 21.5 ± 1.8 | 16.5 ± 1.7 | 33.5 ± 1.0** | 15.6 ± 0.4 |
| Papain (500 μg) plus H2O2 (300 μg) | 40.5 ± 0.9* | 22.0 ± 1.9* | 20.0 ± 2.2 | 17.5 ± 2.0 | 35.5 ± 0.5** | 15.4 ± 0.8 |
| 0.9% NaCl (negative control) | ND | ND | ND | ND | ND | ND |
ND: not detected.
*p < 0.001 when compared to H2O2 (300 μg/disc).
**p < 0.01 when compared to H2O2 (300 μg/disc).