Browsing by Author "Tamer, AU"

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    Thermoactive cellulase-free xylanase production from alkaliphilic Bacillus strains using various agro-residues and their potential in biobleaching of kraft pulp
    Azeri, C; Tamer, AU; Oskay, M
    The four bacterial strains were isolated on media containing xylan and screened for xylanase activity. The bacterial strains (Ag12, Ag13, Ag20 and Ag32) were characterized based on morphological, biochemical and physiological characters and identified as belonging to the genus Bacillus. The effects of different factors such as pH (7.0 - 10.0), temperature (25.0 -50.0 degrees C) and inexpensive agro-residues (wheat straw, wheat bran and corncob) on xylanase production of strains were studied under shake flask conditions. Maximal enzyme activities were obtained by cultivation in birch-wood xylan, but high enzyme production was also obtained on wheat straw and corncob when cultivated at pH 8.5. Under optimized fermentation conditions, no cellulolytic activity were detected on the crude extracts. The effects of temperature (40.0 - 80.0 degrees C), pH (6.0 - 10.0) and salt concentration (1.0, 5.0 and 10.0%) on the xylanases activity were determined. The maximum activity was obtained temperature 60.0 degrees C and pH at 9.0. The enzyme was stable at 60.0 degrees C for more than 60 min, suggesting that the xylanases of Bacillus strains are thermoactive and being of interests for biobleaching processes. The effectiveness of crude xylanases from the strains Ag12, Ag20 and Ag32 on kraft pulp were carried out at pH 9.0 at 60.0 degrees C. Biobleaching studies of kraft pulp with xylanases and its subsequent treatment with 1.0% EDTA (30 min at 50.0 degrees C) and peroxide (80 min at 70.0 degrees C), showed that the enzymes reduced the kappa number by 27.4, 61.7 and 75.3% and enhanced the brightness by 1.0, 1.5 and 3.0% from xylanases produced by strains Ag12, Ag20 and Ag32, respectively. These results suggest that the application of this xylanases to the paper and pulp industry may be very promising.
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    Antimicrobial activity and cytotoxicity of Abies nordmanniana subsp. equi-trojani extracts.
    Sakar, MK; Ercil, D; Tamer, AU; Sahin, N
    Extracts of leaves, cones and twig and stem bark of A. nordmanniana subsp. equi-trojani (collected from Turkey in 1991) exhibited activity against Art salina, Mycobacterium smegmatis, Bacillus subtilis, Sarcina lutea and Staph aureus.
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    ISOLATION AND SCREENING FOR ANTI-MICROBIAL ACTIVITIES OF CULTURABLE MESOPHILIC Streptomyces STRAINS FROM NORTH CYPRUS SOILS
    Oskay, M; Tamer, AU; Karaboz, I
    A total of 249 different Streptomyces strains were isolated from different sites of the North Cyprus habitats for their antimicrobial potential. Out of these, 66 isolates exhibited inhibitory activity against at least one of the tested microorganisms. Approximately, 51% isolates produced antibacterial substances against Gram-positive bacteria, 6% against Gram-negative bacteria, and 23% against both Gram-negative and Gram-positive bacteria, whereas 18% of isolates showed antifungal activity. According to the spectrum of broadness, the two most active isolates were selected, and designed as KGG13 and KVK11. A great variety of morphological, physiological and biochemical features of selected strains were determined for their taxonomic position, and obtained data strongly suggested that these strains belong, to the genus Streptomyces, confirmed by their antimicrobial activity in batch culture. In order to standardize the antibiotic production, some cultural conditions, such as the effect of different temperatures, nature of carbon sources, pH value, and time incubation in h, were determined. The highest antimicrobial activities were obtained when glucose and glycerol at 1% (w/v) was used as sole carbon source, at pHs 7.3 and 7.5 for the strains KGG13 and KVK11, respectively.
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    Pandoraea oxalativorans sp nov., Pandoraea faecigallinarum sp nov and Pandoraea vervacti sp nov., isolated from oxalate-enriched culture
    Sahin, N; Tani, A; Kotan, R; Sedlácek, I; Kimbara, K; Tamer, AU
    Five isolates, designated TA2, TA4, TA25(T), KOx(T) and NS15(T) were isolated in previous studies by enrichment in mineral medium with potassium oxalate as the sole carbon source and were characterized using a polyphasic approach. The isolates were Gram-reaction-negative, aerobic, non-spore-forming rods. Phylogenetic analyses based on 16S rRNA and DNA gyrase B subunit (gyrB) gene sequences confirmed that the isolates belonged to the genus Pandoraea and were most closely related to Pandoraea sputorum and Pandoraea pnomenusa (97.2-99.70/0 16S rRNA gene sequence similarity). The isolates could be differentiated from their closest relatives on the basis of several phenotypic characteristics. The major cellular fatty acid profiles of the isolates comprised C(16:0), C(18:1)omega 7c, C(17:0) cyclo and summed feature 3 (C(16:1)omega 7c and/or iso-C(15:0) 2-OH). On the basis of DNA DNA hybridization studies and phylogenetic analyses, the isolates represent three novel species within the genus Pandoraea, for which the names Pandoraea oxalativorans sp. nov. (TA25(T) =NBRC 106091(T) =CCM 7677(T) =DSM 23570(T)), Pandoraea faecigallinarum sp. nov. (KOx(T) =NBRC 106092(T) =CCM 2766(T) =DSM 23572(T)) and Pandoraea vervacti sp. nov. (NS15(T) =NBRC 106088(T) =CCM 7667(T) =DSM 235711) are proposed.