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Öğe Antimicrobial activity of resins obtained from the roots and stems of Cedrus libani and Abies cilicia(Maik Nauka/Interperiodica, 2002) Kizil, M; Kizil, G; Yavuz, M; Aytekin, CThe antimicrobial activity of the ethanol extract of resins obtained from the roots and stems of Cedrus libani and Abies cilicia has been studied, using the disc diffusion method. The results obtained indicate that crude extracts of the resins of both plants are highly efficient in preventing the growth of microorganisms.Öğe Dyeing of wool fibres with natural dyes: Effect of proteolytic enzymes(Taylor & Francis Inc, 2006) Dogru, M; Baysal, Z; Aytekin, CIn spite of the widespread use of proteins (casein, peptone, etc.) and protein fragments as a substrate for the proteolytic enzymes, a substrate prepared from dyes that adsorb onto appropriate materials, such as wool and cotton, are also used for enzyme activity determination. In the point of view of this thought, it was our aim to develop the substrates which are easily and economically obtainable and also environmentally safer for the frequently used proteolytic enzymes, such as subtilisin carlsberg, trypsin, chymotrypsin, and protease type XVI and, if possible, to prepare the specific substrate at least for one of these enzymes. For this aim, wool was dyed with natural dyes such as juglone, lawsone, berberine, and quercetin. The optimum pH, incubation time, and agitation rate were determinated. The results indicate that, of all the tested enzymes on wool-dye complex as an insoluble subtrate, the most appropriate complex was found to be wool-lawsone complex.Öğe Proteolytic activity of commercial subtilisin from genus Bacillus on some animals milk caseins(Mbr Press Inc, 1997) Aytekin, C; Kaya, Z; Dogru, MCasein is a non-specific substrate for the all proteases. In this study casein was purified from cow, water buffalo, sheep and goat milk and used as a substrate for subtilisin purified preparations from genus Bacillus. On the basis of K-M and V-max value we can say that cow milk casein is the best substrate for the enzyme compared to other animals milk caseins. On the other hand, we have investigated the possible relationship between the Ca2+ and (PO4)(3-) content of casein and the casein appropriate for the enzyme. The cow milk casein with lowermost Ca2+/(PO4)(3-) ratio suggests that these ions may have an influence on enzyme-substrate interaction. Although this enzyme is active in the pH range of 7-11 and a temperature range of 25-60 degrees C, the optimal pH and temperature for the enzyme against cow milk casein were found to be 10,0 and 37 degrees C respectively.Öğe Solid state fermentation for production of ?-amylase by a thermotolerant Bacillus subtilis from hot-spring water(Elsevier Sci Ltd, 2003) Baysal, Z; Uyar, F; Aytekin, CThe production of extracellular a-amylase by thermotolerant Bacillus subtilis was studied in solid state fermentation (SSF). The effect of wheat bran (WB) and rice husk (RH) was examined. The appropriate incubation period, moisture level, particle size and inoculum concentration was determined. Maximum yields of 159,520 and 21,760 U g(-1) were achieved by employing WB and RH as substrates in 0.1 M phosphate buffer at pH 7 with 30% initial moisture content at 24 and 48 h. Particle size and inoculum concentration were found to be 1000 pm, 20% and 500 mum, 15% for WB and RH, respectively. Enzyme yield was 7.3-fold higher with WB medium compared with RH. (C) 2002 Elsevier Science Ltd. All rights reserved.Öğe A study for determining mechanism of subtilisin-casein interaction by using inhibition kinetics data(Mbr Press Inc, 1998) Aytekin, C; Baysal, ZKCasein is a non-specific substrate for the an extacellular protease subtilisin. In this study tyrosine, tryptophan, cysteine, phenol and ethyl-methane sulfonate (EMS) were added to the enzyme-substrate medium in appropriate concentrations to investigate their kinetics effect. The additions of these compounds to incubation medium were found cause to different kinds of inhibitions. The inhibition effects of tyrosine, tryptophan and phenol indicate that the enzyme attacks the aromatic amino acid residues on the substrate. Because the sulfhydryl group of cysteine is a very strong induce protonates the imidazol groups of histidine on the enzyme. This can be explained as cysteine effected that the histidine residues decrease the nucleophilicity of the serine residues in the active site of enzyme. On the other hand the effect of mutagenic compound EMS caused to competitive inhibition. It was observed that this result to be in contradiction with alkylation reagents effect that cause to irreversible inhibition.
