Mehlika Benli

Antimicrobial activity of endemic Crataegus tanacetifolia (Lam.) Pers and observation of the inhibition effect on bacterial cells.

Up to now an increasing number of antibiotic‐resistant bacteria have been reported and thus new natural therapeutic agents are needed in order to eradicate these pathogens. Through the discovery of plants such as Crataegus tanacetifolia (Lam.) Pers that have antimicrobial activity, it will be possible to discover new natural drugs serving as chemotherapeutic agents for the treatment of nosocomial pathogens and take these antibiotic‐resistant bacteria under control. The objective of the present study was to determine antimicrobial activity and the activity mechanism of C. tanacetifolia plant extract. The leaves of C. tanacetifolia, which is an endemic plant, were extracted using methanol and tested against 10 bacterial and 4 yeast strains by using a drop method. It was observed that the plant extract had antibacterial effects on Bacillus subtilis, Shigella, Staphylococcus aureus, and Listeria monocytogenes among the microorganisms that were tested. Minimum inhibitory concentration (MIC) results obtained at the end of an incubation of 24 h were found to be ≥6.16 mg ml−1 for B. subtilis, <394 mg ml−1 for Shigella, and ≥3.08 mg ml−1 for L. monocytogenes and S. aureus and minimum bactericidal concentration (MBC) were found as ≥24.63 mg ml−1 for B. subtilis, ≥394 mg ml−1 for Shigella, ≥6.16 mg ml−1 for L. monocytogenes, and ≥98.5 mg ml−1 for S. aureus. According to the MBC results, it was found that the plant extract had bactericidal effects and in order to explain the activity mechanism and cell deformation of bacterial strains treated with plant extract, the scanning electron microscopy (SEM) was used. The results of SEM showed that the treated cells appeared shrunken and there was degradation of the cell walls. This study, in which the antibacterial effect of C. tanacetifolia was demonstrated, will be a base for further investigations on advanced purification and effect mechanism of action of its active compounds. Copyright

The effects of using transglutaminase, exopolysaccharide‐producing starter culture and milk powder on the physicochemical, sensory and texture properties of low‐fat set yoghurt

This study focused on the effects of transglutaminase (TGase), exopolysaccharide (EPS)-producing starter culture or skim milk powder addition on some properties of low-fat set yoghurt. The incorporation of TGase to yoghurt did not affect the acidity of the experimental samples. However, the proteolytic activity of the starter culture significantly decreased in TGase-treated yoghurt. Addition of TGase to yoghurt with a low dry matter content (11.08%) resulted in low serum separation and gel firmness and viscosity close to those of yoghurt with a higher dry matter content (14.81%). According to the sensory results, it would be possible to produce an acceptable product with a low dry matter and low fat content using TGase. The results shown that the use of EPS-producing starter cultures for the purpose of improving the texture properties of low dry matter content yoghurt could not be recommended.

Purification and characterization of intracellular and extracellular α-glucosidases from Geobacillus toebii strain E134

Two different α‐glucosidase‐producing thermophilic E134 strains were isolated from a hot spring in Kozakli, Turkey. Based on the phenotypic, phylogenetic and chemotaxonomic evidence, the strain was proposed to be a species of G. toebii. Its thermostable exo‐α‐1,4‐glucosidases also were characterized and compared, which were purified from the intracellular and extracellular fractions with estimated molecular weights of 65 and 45 kDa. The intracellular and extracellular α‐glucosidases showed optimal activity at 65 °C, pH 7·0, and at 70 °C, pH 6·8, with 3·65 and 0·83 Km values for the pNPG substrate, respectively. Both enzymes remained active over temperature and pH ranges of 35–70 °C and 4·5–11·0. They retained 82 and 84% of their activities when incubated at 60 °C for 5 h. Their relative activities were 45–75% and 45–60% at pH 4·5 and 11·0 values for 15 h at 35 °C. They could hydrolyse the α‐1,3 and α‐1,4 bonds on substrates in addition to a high transglycosylation activity, although the intracellular enzyme had more affinity to the substrates both in hydrolysis and transglycosylation reactions. Furthermore, although sodium dodecyl sulfate behaved as an activator for both of them at 60 °C, urea and ethanol only increased the activity of the extracellular α‐glucosidase. By this study, G. toebii E134 strain was introduced, which might have a potential in biotechnological processes when the conformational stability of its enzymes to heat, pH and denaturants were considered. Copyright

Fine structural analysis of the stinger in venom apparatus of the scorpion Euscorpius mingrelicus (Scorpiones: Euscorpiidae)

In this study, the morphology, histology and fine structure of the stinger, a part of the venom apparatus of Euscorpius mingrelicus (Kessler, 1874) (Scorpiones: Euscorpiidae) were studied by light microscopy and transmission electron microscopy (TEM). The stinger, located at the end section of the telson, is sickle-shaped. The venom is ejected through a pair of venom pores on its subterminal portion. Both venom ducts extend along the stinger without contact with each other since they are separated by connective tissue cells. The stinger cuticle is composed of two layers. Additionally, there are many pore canals and some hemolymph vessels in the cuticle. This work constitutes the first histological and fine structure study on Euscorpius mingrelicus stinger.

A STUDY ON USING EXOPOLYSACCHARIDE-PRODUCING CULTURE IN LOW FAT KASAR CHEESE

In this study, the impacts of an exopolysaccharide-producing (EPS+) starter culture on some quality characteristics of low fat Kasar cheese samples were investigated. For this purpose, four cheese samples were manufactured: cheeses containing 20% fat-in-dry matter with added 0.5% EPS+ and 1.0% EPS+ culture (EPS+0.5 and EPS+1.0), control cheese containing 20% fat-in dry matter (K20) and control cheese containing 40% fat-in-dry matter (K40). The samples were allowed to ripening for 90 days at 4 ± 1 °C and were evaluated for chemical, physical, sensory and microstructure qualities on the 1 st, 15th, 30th, 60th and 90th days of ripening. SEM images showed that textural characteristics of low-fat cheese samples could be improved by using EPS+ starter culture and of which had similar texture to the control cheese with 40% fat-in-dry matter. However, it was determined that defects in body and flavor became definite with an excessive increase in moisture level and the cheese with 1.0% EPS+ culture preferred less than the cheese with 0.5% EPS+ culture.