1962 Volume 27 Issue 5 Pages 231-238
1. Erwinia carotovora produces two kinds of pectin depolymerases (DP), one having the optimum pH at about 8.5 (DPa) and the other at about pH 4.0 (DPb).
2. The initial pH of culture medium affected the production of DP, i. e., in synthetic medium A containing pectin (see Table 2), both DP, especially DPb, were scarcely produced in case the initial pH was 5.5 or 5.8, but abundantly in case that was above 6.0. In the former case, pH shift toward 4.0∼4.5 and its stagnation at this level for a long time during the culture period were the main factors which depressed the enzyme secretion (see Table 1 and Fig. 1).
3. In beef extract broth DPa was secreted to varying degrees of activity according to the isolates used, whereas DPb was scarcely secreted irrespective of isolates, even in the presence of pectin. Addition of 0.5per cent peptone to the synthetic medium A stimulated the secretion of DPa at the primary stage of growth, whereas somewhat depressed the secretion of DPb. Addition of 0.5per cent mono-sodium glutamate to the synthetic medium A stimulated the secretion of both enzymes to a great extent. In media containing glucose as the sole carbon source, DPb was scarcely produced, whereas DPa was secreted to a relatively high degree. The media used by Echandi et al. (1957) and by Wood (1955) in their studies on pectolytic enzymes were unfavorable for the production of DPb; especially in the latter no DPb activity was detected.
DPa was usually secreted faster than DPb. In the most suitable medium for depolymerase productions, DPa was secreted rapidly from the primary stage of growth, reaching its maximum accumulation after 48 hours. DPb was secreted much more slowly, reaching its maximum accumulation on 3rd to 8th day after inoculation, the date varying according to the isolates used.
4. Both depolymerases, especially DPb, were scarcely secreted in media of low salt concentrations, even if it contained enough pectin as the substrate. This may be due to the pH shift toward 4.0∼4.5 because of the low buffering effect (see Table 4 and Fig. 3).
5. Both depolymerases were produced more abundantly in flask culture than in test tube culture, suggesting that the larger was the area of air contact with the medium surface the larger was the amount of enzymes produced. This effect of air was not so intense as in the case of PME production previously reported (Table 5 and Fig. 4).
6. The activity of both depolymerases, after 5 day-incubation in the synthetic medium A, differed according to the isolates used (see Table 6).