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    Cultivable sponge-associated actinobacteria: Phylogenetic diversity and antimicrobial activities
    (Elsevier Science Bv, 2012) Oner, Ozlem; Ekiz, Guner; Hames-Kocabas, E. Esin; Demir, Volkan; Gube, Ozkan; Ozkaya, F. Can; Yokes, M. Baki; Uzel, Atac; Bedir, Erdal
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    Increased alkalotolerant and thermostable ribonuclease (RNase) production from alkaliphilic Streptomyces sp M49-1 by optimizing the growth conditions using response surface methodology
    (Springer, 2013) Demir, Tugce; Gube, Ozkan; Yucel, Mesut; Hames-Kocabas, E. Esin
    Total of 171 alkaliphilic actinomycetes were evaluated for extracellular RNase production and Streptomyces sp. M49-1 was selected for further experiments. Fermentation optimization for RNase production was implemented in two steps using response surface methodology with central composite design. In the first step, the effect of independent fermentation variables including temperature, initial pH and process time were investigated. After identification of carbon and nitrogen sources affecting the production by one variable at a time method, concentrations of glucose and yeast extract and also inoculum size were chosen for the second central composite design. A maximum RNase activity was obtained under optimal conditions of 4.14 % glucose concentration, 4.63 % yeast extract concentration, 6.7 x 10(6) spores as inoculum size for 50 ml medium, 42.9 A degrees C, 91.2 h process time and medium initial pH 9.0. Optimum activity of the enzyme is achieved at pH 11 and temperature 60 A degrees C. The enzyme is highly stable at pH range 9.0-12.0 and at 90 A degrees C after 2 h. Statistical optimization experiments provide 2.25 fold increases in the activity of alkalotolerant and thermostable RNase and shortened the fermentation time compared to that of unoptimized condition. The members of Streptomyces can be promising qualified RNase producer for pharmaceutical industries.
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    Synthesis, Structural Analysis and Antimicrobial Activities of Novel Water Soluble Ionic Liquids Derived from N-Heterocyclic Carbene Salts
    (Croatian Chemical Soc, 2016) Kunduracioglu, Ahmet; Gube, Ozkan; Hames-Kocabas, Elif Esin; Eyupoglu, Volkan; Sonmez, Fatih
    Six N-heterocyclic Carbene based Ionic Liquids (ILs) have been synthesized by conventional methods. The ILs were spectroscopically characterized by NMR and FT-IR techniques. Their in vitro antimicrobial activities were determined towards gram-positive and gram-negative bacterias and yeast strains using minimum inhibition concentration (MIC) assay. The best inhibition performances were obtained with compound 1 due to its more hydrophilic nature compared with the others. It exhibited 1 mg L-1 MIC value against to the most bacteria while the others showed 4 mg L-1.