Çetin Aytekin

Solid state fermentation for production of α-amylase by a thermotolerant Bacillus subtilis from hot-spring water

Abstract The production of extracellular α-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 μm, 20% and 500 μm, 15% for WB and RH, respectively. Enzyme yield was 7.3-fold higher with WB medium compared with RH.

In Vitro Antimicrobial and Antioxidant Activity of Ethanol Extract of Three Hypericum and Three Achillea Species From Turkey

The present study was conducted to determine the antimicrobial, antifungal and antioxidant activity of the ethanol extract of Hypericum scabrum L (HSm), Hypericum lysimachioides var. lysimachioides (HL), and Hypericum retusum Aucher (HR) and ethanol extracts of Achillea aleppica D.C. subsp. aleppica (AA), Achillea aleppica D.C. subsp. zederbaueri (Hayek) Hub.-Mor (AZ), and Achillea biebersteinii Afan. (AB). The antioxidant properties of extracts were evaluated using different antioxidants tests, including reducing power, free radical scavenging, deoxyribose assay, metal chelating activities and determination of total phenolic compounds. The extracts obtained from Hypericum and Achillea species showed high antioxidant properties. The protective effects of plant extracts were compared with a well known antioxidant, Butilated Hydroxytoluen (BHT) and α-tocopherol. Total antioxidant activity of ethanol extracts of plants were also tested by using ferric thiocyanate (FTC) and thiobarbituric acid (TBA) methods. Antioxidative activities of plant extracts were found to be comparable with Vitamin E. The results showed that the ethanol extracts of all tested plant exhibited different activity against tested microorganisms. Since most of the studied extracts have good antimicrobial and antioxidant activity, it might be possible to use them as natural food additives that act both as antioxidants and as spices.

Antimicrobial activity of the resins obtained from the roots and stems of Cedrus libani and Abies cilicica.

The 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.

Removal of methylene blue from aqueous solutions onto Bacillus subtilis: determination of kinetic and equilibrium parameters

AbstractIn the present study, Bacillus subtilis, a Gram-positive bacteria, was used in dried biomass form as biosorbent for removal of methylene blue (MB) from aqueous solutions. Batch adsorption tests were performed at different contact times, temperatures, pH, adsorbent doses, and initial dye concentration. The adsorption isotherms are described by means of the Langmuir and Freundlich isotherms. It was found that the Langmuir equation fit better than the Freundlich equation. Maximum biosorption capacity was found to be 169.49, 178.57, and 181.82 mg g−1 at 298, 308, and 318 K, respectively. The adsorption kinetics of MB could be described by the pseudo-second-order reaction model. The activation energy of the biosorption (Ea) was determined as 11.30 kJ mol−1 at initial concentration of 50 mg L−1. Free energy of adsorption (ΔG°), enthalpy (ΔH°), and entropy (ΔS°) changes were calculated to predict the nature of adsorption. The estimated values for ΔG° were −21.22, −22.02, and −23.01 kJ mol−1 at 298, 308, ...

Dyeing of wool fibres with natural dyes: effect of proteolytic enzymes.

Abstract In 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.

Antimicrobial Activity of the Tar Obtained from the Roots and Stems of Pinus brutia

The antimicrobial activity of the crude and methanol, hexane, chloroform, petroleum ether, ethyl acetate and n -butanol extracts of tar obtained from the roots and stems of Pinus brutia Ten., used in the folk medicine of Turkey, were screened in vitro for antimicrobial activity against clinically isolated bacterial strains: Staphylococcus aureus (15 isolates), Streptococcus pyogenes (12 isolates), Escherichia coli (17 isolates) and the yeast fungus Candida albicans (3 isolates) by the paper disc diffusion method. Results revealed that a crude extract of the tar is highly effective against all tested microorganisms by preventing their growth to a significant extent. All the organic extracts showed similar moderate antimicrobial activity against tested microorganisms at a concentration of 80 µg/mL. The results demonstrate that the crude tar extract has a very broad spectrum of activity, and suggests that it may be useful in the treatment of various microbial infections. The results suggest that traditional folk medicine could be used a guide in our continuing search for new natural products with potential medicinal properties.

Use of Natural Dye‐Casein Complexes: Effect of Proteolytic Treatment

Abstract The activity of proteolytic enzymes is commonly measured using casein as a substrate. A modified caseinolysis assay was developed with natural dyes such as juglone, lawsone, berberine, and quercetin for Subtilisin carlsberg, protease type XVI, and trypsin, respectively. The pH dependence and incubation time were determined. Km, Vmax, and kcat/Km values were also determined for these enzymes. Lawsone was found to be a better substrate than the others.