carbon source followed by cultures containing starch. Cultures containing fructose, maltose, xylose or cellulose did not yield any detectable amounts of the antibiotic. The results also showed that the increase of glycerol level in the culture from 10g/l to 12.5 g/l led to 1.32-fold increase in antibiotic production (Fig 2). The utilisation of glycerol and starch by S. violatus for growth and production of the antibiotic indicates the presence of an active uptake system for these substrates. Glycerol was also found to be used as a sole carbon source by other Streptomyces species.
2. Effect of glycerol concentration on the production of antibiotic byStreptomyces violatus at different incubation periods: a) 4 days, b) 7 days and c) 10 days.
2 - Effect of different carbon sources on the production of antibiotic by S. violatus.
. 2.2 Influence of nitrogen source results revealed that the level of antibiotic production may be greatly influenced by the nature, type and concentration of the nitrogen source supplied in the culture medoium (Table 3). Similar observations have been reported by many investigators. The highest antibiotic production was obtained in cultures of S. Violatus containing sodium nitrate or potassium nitrate as a nitrogen source, followed by cultures containing peptone, alanine, monosodium glutamate or phenylalanine. However, cultures containing asparagine or ammonium citrate did not yield any antibiotic activity and showed lowest growth. The results also showed that the concentration of NaNO3 (Fig. 3) greatly influenced the production of the antibiotic by S. violatus cultures, while the maximum antibiotic yield was obtained in cultures suplemented with 2.5 g/l NaNO3. These results are in partial agreement with those of other investigators. A negative effect of asparagine on the production of cephamycin C was also observed on cultures of S. cattleya, S. latamdurans and Cephalosporium acremonium.
Figure 3. Effect of sodium nitrate (NaNO 3) concentration on the production of antibiotic by Streptomyces violatus at different incubation periods: a) 4 days, b) 7 days and c) 10 days.
3 - Effect of different nitrogen sources on the production of antibiotic by S. violatus.
2.2.3 Influence of potassium phosphate and magnesium sulphate salts is a major factor in the synthesis of a wide range of antibiotics. However, an excessive amount of inorganic phosphate suppresses the production of antibiotics such as tetracycline, actinomycin and candicidin (Kishimoto et al. 1996). The results of the present work (Fig 4) showed that KH2PO4 was not favourable for the production of antibiotic by S. violatus, while K2HPO4 at a concentration of 1g/l yieldes an inhibition zone of 22 mm, equivalent to an antibiotic concentration of 128 ?g/ml. It was also observed that addition of a mixture of both phosphate salts (KH2PO4 and K2HPO4) showed the most positive effect on the production of antibiotic by S. violatus. The antibiotic concentration reached its maximum value (245?g/ml) when using a phosphate salt mixture of 1g/l, showing a 1.9-fold and 6.1-fold increase when compared to the highest values ??obtained when K2HPO4 and KH2PO4 were individually supplied to the medium , respectively. These results are in agreement with those reported by other investigators. The results also showed that addition of 0.5g/l magnesium sulphate to the culture medium was optimal for the production of a maximum yield of antibiotic by S. violatus (Fig 5). At this MgSO4.7H2O concentration, the antibiotic yield was 4.2-fold than that in cultures devoid of magnesium sulphate. The importance of magnesium sulphate for antibiotic production by other Streptomyces species has been reported by several investigators. The effects of magnesium availability are presumably due to requirements of this cation for protein synthesis, and its depletion may restrict enzyme synthesis and activity.
4. Effect of different (a) KH2PO4 and (b) K2HPO4 concentrations on the production of antibiotic by Streptomyces violatus.
results also showed that addition of 0.5g/l magnesium sulphate to the culture medium was optimal for the production of a maximum yield of antibiotic by S. violatus (Fig 5). At this MgSO4.7H2O concentration, the antibiotic yield was 4.2-fold than that in cultures devoid of magnesium sulphate. The importance of magnesium sulphate for antibiotic production by other Streptomyces species has been reported by several investigators. The effects of magnesium availability are presumably due to requirements of this cation for protein synthesis, and its depletion may restrict enzyme synthesis and activity (Aasen et al. 1992; mNatsume et al. 1994).
5. Effect of (...
