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    A cellulase-free, thermoactive, and alkali xylanase production by terrestrial Streptomyces sp CA24
    (Tubitak Scientific & Technological Research Council Turkey, 2013) Porsuk, Ilknur; Ozakin, Suleyman; Bali, Bulent; Yilmaz, Ebru Ince
    Microbial xylanases have attracted much attention because of their applications in industrial processes during the past few decades. Sixty-five terrestrial actinomycetes previously isolated from rhizospheric soils of endemic plants were tested for their ability in production of xylanase. The results revealed that 33 isolates could degrade xylan on both solid and liquid media. Extracellular xylanase production by these isolates was characterized during their growth in liquid medium. Streptomyces sp. CA24, one of the most active strains, was selected for optimization of xylanase production. The enzyme secretion was enhanced when the medium was supplemented with oat spelt xylan (0.5%) and yeast extract (0.5%) at pH 10.0. Optimization of the culture conditions resulted in a 5-fold enhancement in enzyme production (255 U/mL). The most important characteristic of the enzyme is its production over a broad pH range of 6.0-10.0 during all stationary phases. The cellulase-free xylanase was optimally active at 60 degrees C and almost 90% stable after 4 h at 50 degrees C. The high levels of enzyme production obtained under alkali batch cultivation conditions, coupled with no production of cellulase, suggests the use of the local terrestrial strain Streptomyces CA24 and/or its enzyme in industrial processes such as pulp and paper production.
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    Öğe
    Molecular characterization of rhizospheric soil streptomycetes isolated from indigenous Turkish plants and their antimicrobial activity
    (Springer, 2008) Yilmaz, Ebru Ince; Yavuz, Murat; Kizil, Murat
    As part of a research program whose aim is to determine the diversity of streptomycetes in order to discover new bioactive secondary metabolites, rhizosphere soils of three indigenous plants were analyzed. A total of 55 actinomycetes were isolated using three different medium from the samples. The rhizospheric soil of the plant Aethionema dumanii gave the highest number of actinomycetes, i.e., 42% versus 27% and 31% for the soils from Salvia aytachii and Achillea ketenoglui, respectively. The AIA is the most favorable medium for the isolation of the actinomycetes from different rhizospheric soils. 16S rDNA sequence analysis revealed that while some isolates belong to different cluster groups such as Streptomyces lydicus, S. rochei, S. microflavus, S. griseoflavus, S. albidoflavus and S. violaceusniger, the majority of the sequences did not considerable clustered with the member of different Streptomyces groups. The in vitro antimicrobial activities of the crude organic and aqueous extracts of isolates were screened using a disc diffusion assay against a panel of bacteria and C. albicans. A total of 22 isolates showed antimicrobial activity. The antibacterial action of the extracts is more pronounced on Gram-positive than on Gram-negative bacteria in most cases. About 18% of the actinomycetes showed also antifungal activity. Study of the influence of two different culture media on production of bioactive molecules showed that the higher antimicrobial activity was obtained in M2 when compared to TSB. The results from this study provide evidence that the streptomycetes in the rhizosphere soils could be promising sources for antimicrobial bioactive agents.