Xylanolytic activities of some streptomycetes with special reference to xylanase of s.poonensis and s. libani

The objective of this work was to study the xylanolytic activities of 15 streptomycetes species. The values of xylanase productivity obtained revealed that Streptomyces poonensis, Streptomyces libani and Streptomyces zaomyceticus showed the highest levels of productivity. The effect of culture conditions and medium composition on the production of xylanase by the former two species was studied. The highest yield of xylanase was obtained after 72-96 hour of cultivation when the pH of culture medium was controlled at 6.5-7.5. The best sources which enhanced the productivity of extracellular xylanase were xylan, casein or peptone and K2HPO4. Some properties of crude xylanase produced by S. poonensis were also studied

Antimicrobial and antitumor activities of three new antibiotics and their effects on protein and nucleic acids synthesis

The anti-microbial activity, toxicity and antitumor activity of three new antibiotics were investigated in relation to their effects on protein, DNA and RNA synthesis of some gram positive and gram negative bacteria. The results indicated that one antibiotic demethyltetracycline did not show any toxic effect on normal Swiss albino mice at a concentration up to 500 mg/kg body weight, meanwhile it exhibited an in vivo antitumor effect against Ehrlich ascites tumor. However, granaticin and caeseorhodomycin showed a slight toxicity [10%] to normal Swiss albino mice at a concentration of 450 mg/kg body weight, but they did not show a significant antitumor effect against Ehrlich ascites tumor. The three tested antibiotics acted as inhibitors to protein and DNA synthesis, but they had no marked effect on RNA synthesis

Regulation of production and some properties of chitinase produced by streptomyces cyaneogriseus strain.

Fourteen Streptomyces isolates were assayed for their chitinolytic activities. All the isolates were positive chitinase producers. Streptomyces cyaneogriseus in a 6-day-old shaken culture at 30 degree and an initial pH of 7.5 was the most promising chitinase producer. Chitinase yields increased as the amount of chitin in the culture Chitinase medium increased [0.5-2.0%] and the maximum activity was obtained with 1.5% colloidal chitin. The addition of yeast extract [0.3%] gave 47% increase in chitinase production and reduced the incubation period for five days. Some properties of the crude enzyme produced by St. cyaneogriseus were studied. A maximal enzyme activity was reached at pH of 6.5-7.0 and 40 degree for 30 min. The enzyme was stable below 50C and became completely inactive at 65C

Demethyltetracycline biosynthesis by streptomyces aureofaciens sub-species viridulaus as influenced by medium composition

The influence of different nutritional compounds on demethyltetracycline by Streptomyces aureofaciens subspecies viridulaus was examined. Of the variety of carbon sources, nitrogen and phosphorus compounds tested; fructose, sodium nitrate and sodium dihydrogen phosphate supported the highest demethyltetracycline production. The addition of ferrous sulfate and nicotinamide [as trace element and vitamin, respectively] stimulated the biosynthesis of the antibiotic. In the majority of cases, the biomass yield ran parallel with the antibiotic production

Biosynthesis of demethyltetracycline by a strain of streptomyces

Streptomyces aureofaciens sub-species viridulaus [isolate No. MN 27] was found to produce a yellowish orange pigment. This pigment was extracted from the fermentation medium by chloroform at neutral pH [pH 7], chromatographically purified and obtained as orange powder. The purified pigmented substance exhibits a strong antimicrobial activity towards Gram positive and Gram negative bacteria [MIC =200, 50, 5, 100, 35 ug/ml against B. Subtilis, B. Megaterium, B. Cereus, Athrobacter simplex, and E. coli, respectively]. The physicochemical characteristics of the purified substance were investigated and accordingly the present antibiotic pigment was identified as a new antibiotic belonging to tetracycline group of antibiotics having indicator properties for which the name demethyltetracycline was suggested