Biosynthetic Conditions And Extration Method Of Antibiotic Inhibiting Pseudomonas Aeruginosa In Streptomyces Strain SM037

Ninty-eight Actinomycete strains producing antimicrobial substances to restrain the growth of Pseudomonas aeruginosa, were isolated from the soil with 1400 ppm of La2O3 in it. Among these strains, SM037 had the strongest activity against P. aeruginosa, Staphylococcus aureuss(Gram-positive bacteria), Bacillus thuringiensis(Gram-positive bacteria), Escherichia coli(Gram-negative bacteria), Salmonella pullorum(Gram-negative bacteria) and Candida albicans(fungal). That meant the strain SM037 was a strain of yielding broad-spectrum antibiotic, and has been studied further in this paper.According to the morphology of mycelium and spores in Gause's syntetic No1 media, the growth features in different media, the capability of using of a series carbon resources, the physiol-biochemical characteristics including the ability to liquate gelatin, to hydrolyze starch and cellulase and to produce H2S, the SM037 was identified as Streptomyces.canaries var.canaries tentatvily.For increasing production of antibiotic, the liquid media composition was studied. Antibiotic content of the fermented liquid was determined by cylinde-plate method. The screening data indicated that the optimal carbon source was soluble starch, and the optimal nitrogen source was KNO3. By changing the ratio of carbon source and nitrogen source, and by using the orthogonal tests of carbon, nitrogen and phosphate, the optimal proportion of these components was obtained. The percentage of these components was as following, soluble starch 4%, KNO3 0.2% and K2HPO4 0.05%.The study showed that suitable technical parameters in fermentation were: initial pH 7.0~7.5, 7% inoculum in a 50 ml liquid (in 250ml flask) at 28℃. Under the suitable fermentation condition and in the optimal media the antibiotic yield of strain SM037 reached maximum during 96～108 hours. After the optimization studying of fermentation conditions, the potency unit of fermentation liquor was increased from 326u·ml-1 to 1592u·ml-1.The ability of biological active substances in fermentation liquid kept stable in 60℃water-bath for 30min, started to decline at 70℃, and the activity reduced fast between 80 and 121℃. In the alkali environment, the antimicrobes ability of fermentation liquid slowly reduced with the increasing of pH value, and on the other hand, as the pH value reducing, the antiorganism activity reduced quickly in acidic environment. The study showed that the active substances is stable in alkali environment and unstable in acidic environment. The biological active substances were purified through employing different fractionation and purification methods such as extracted by ethyl acetate, chromatographed by 200~300 size silica column, and determined by silica GF254, By MS checking, three main substances were found, which named S-I, S-II, and S-III. According to the analysis of MS data and the searching results of the Biological Active Substance Data Base, the structures of S-I, S-II, and S-III were determined primarily as C10H15N3O3, C17H28N8O8, and C24H52N8O2 which are Eulicin, Cairomycin B and Antibiotic LL-AC 541 respectively.