or acetone. By the extraction with nonpolar solvents, a most part of water soluble compounds present in the medium is eliminated. The crude isolate obtained is used as a material for further separation processes.antibiotic producers often synthesize a number of compounds or derivatives of the desired compound that have to be separated from the antibiotic produced. The separation is carried out using standard operations such as an extraction into another solvent, chromatography techniques and, in the end, precipitation or crystallization.
2. Experemental part
Streptomyces violatus showed the highest antimicrobial activity in static cultures after 7 days incubation at 30 ° C. The antibacterial substance was more active against Bacillus subtilis and Staphyllococcus aureus than Escherichia coli or Sarcina lutea. Growth of S. violatus and production of antibiotic in a starch-nitrate medium were monitored over a period of 14 days. The organism produced a blue pigment associated with the antibiotic appearance in the cultures. Optimization of antibiotic production in batch cultures has been carried out. Substitution of starch by glycerol at a concentration of 12.5 g/l showed 1.32-fold increase of antibiotic production. Cultures containing sodium nitrate (2.5g/l) showed the highest antibiotic production followed by peptone, alanine, monosodium glutamate or phenylalanine. A mixture (w/w) of K2HPO4 and KH2PO4 (1g/l) yielded 1.9-fold and 6.1-fold increase in antibiotic production compared to cultures individually supplied with K2HPO4 or KH2PO4, respectively. The presence of ferrous sulphate and manganese chloride improved the production of the antibiotic. An inoculum size of 4x106 spores/ml and initial pH 7.0 at 30 ° C were optimum for a maximum antibiotic production of 268?g/ml in the culture filtrates of S. violatus [26].
2.1 Abstract to Streptomyces violatus
are the source of several useful antibiotics that are used not only in the treatment of various human and animal diseases but also in agriculture and biochemistry as metabolic poisons .At least 70 of the approximately 100 marketed antibitics used for the treatment of infections in humans are derived from substances produced by Streptomyces spp., for example Streptomyces aureofaciens is an important industrial microorganism as a producer of chlortetracycline and tetracycline. Discovery of new antibiotics produced by streptomycetes still continues, such as noboritomicins A and B produced by S. Noboritoensis [27], actinomycins X2 produced by S. nasri (El-Naggar et al. 1998), tetrodecamycin produced by S. nashvillensis MJ885-mF8, demethyltetracycline produced by S. aureofaciens and pyrroindomycins produced by S. rugosporus (Abbanat et al. 1999). The ability of streptomycete cultures to form antibiotics is not a fixed property but can be greatly increased or completely lost under different conditions of nutrition and cultivation (Waksman 1961). Therefore, the medium constitution together with the metabolic capacity of the producing organism greatly affects antibiotic biosynthesis. Changes in the nature and type of carbon, nitrogen or phosphate sources and trace elements have been reported to affect antibiotic biosynthesis in streptomycetes. In addition, antibiotic productivity tendes to decrease when metal ion deficient media are used and when the inocula are incubated for long periods and at high temperatures. The present study describes the production of an antimicrobial substance MSW2000 produced by a local isolate of Streptomyces violatus. Improvement of antibiotic production was acheived by optimization of the cultural conditions and by developing of a defined medium for the biosynthesis of the antibiotic.
. 1.1 Producer of experimentorientalis, S. violatus, S.craterifer and S. astreogriseus were isolated from garden soil, Faculty of Science, Alexandria, Egypt. Soil samples were collected at a depth of 5-10 cm. These strains were identified according to the International Streptomyces Project (ISP) [28] anisms: The following test organisms were used for the bioassay of the antibiotic during the screening experiment: Staphylococcus aureus (209 P FDA), Sarcina leutea (NCIB 495) , Bacillus subtilis (ATCC 6051), Escherichia coli (NCIB 1186) and Klepsiella pneumonia (Local isolate). S. aureus was used as a target organism in all other experiments. of Streptomyces violatus for antibiotic production: For studies of antibiotic production, starch-nitrate medium was used as a basal medium. It was composed of (g/l): Starch, 10.0, NaNO3, 2.5, K2HPO4, 1.0, KH2PO4,1.0, MgSO4.7H2O, 0.5, KCl, 0.5, trace salt solution 1.0 ml (CuSO4.5H2O (0.64 g/l ), FeSO4.7H2O (0.11 g/l), MnCl2.4H2O (0.79 g/l) and ZnSO4.7H2O (0.15 g/l), distilled water, 1.0 litre. Medium pH was adjuste...
