TABLE 1.
Effect of the medium composition on growth and caseinolytic protease productiona
| Nutrient | Cell growth (CFU [108]/ ml) | Protease (EU/ml) | Protease production (EU/ml)/(CFU [108]/ml) | Caseinolytic activity (%)b |
|---|---|---|---|---|
| None (peptone) | 25.7 | 507.6 | 19.7 | 100 |
| Lactose | 28.1 | 560.2 | 19.9 | 101.6 ± 2 |
| Galactose | 39.1 | 436.6 | 11.1 | 56.6 ± 3 |
| Sucrose | 30.3 | 446.5 | 14.7 | 74.6 ± 2 |
| Glycerol | 48.2 | 173.5 | 3.6 | 18.2 ± 1 |
| Mannitol | 62 | 151.9 | 2.4 | 12.3 ± 1 |
| Fructose | 63.8 | 52.3 | 0.8 | 4.1 ± 0 |
| Maltose | 71.6 | 383.5 | 5.3 | 27.1 ± 1 |
| Glucose | 63.2 | 59.8 | 0.9 | 4.7 ± 0 |
| Peptone + NH4Cl | 25.9 | 117 | 4.5 | 22.8 ± 1 |
| Casamino Acids | 15.1 | 0 | 0 | 0 ± 0 |
| Casamino Acids + NH4Cl | 14.8 | 0 | 0 | 0 ± 0 |
| NB | 17.5 | 382.6 | 21.8 | 110.8 ± 3 |
a
For nutrient studies cells were grown on 1% (wt/vol) peptone medium containing 5 mM MgCl2, 2.9 mM K2HPO4, and the indicated nutrient source (50 mM for each carbohydrate and NH4Cl; 1% (wt/vol) for glycerol, mannitol, and Casamino Acids). Samples were obtained at stationary growth phase (24 h), and caseinolytic activity was determined by using 120 μl of cell-free supernatant. Values are averages ± standard deviations for three independent experiments.
b
Percent caseinolytic activity in each medium expressed in relation to the activity in peptone medium (100%).