Sebnem Harsa

Prevalence and Antibiotic Resistance of Foodborne Staphylococcus aureus Isolates in Turkey

Abstract In this study, 154 Staphylococcus aureus isolates were detected from 1070 food samples (14.4%) collected from seven cities in Turkey. Antimicrobial susceptibility testing against 21 antibiotics was performed by agar disk diffusion method, and those isolates resistant to any antibiotic were further analyzed to determine minimum inhibitory concentration by E-test and polymerase chain reaction analysis of vanA and mecA genes. According to disk diffusion test results, a total of 139 strains were resistant to at least one tested antibiotic, with 39 (25.3%) strains being multidrug resistant (MDR) and the other 15 strains being susceptible to all antibiotics. Penicillin G, linezolid, erythromycin, and tetracycline took up 71.4%, 23.4%, 18.2%, and 15.6% of the tested strains, respectively. In addition, all of the strains were susceptible to vancomycin, oxacillin, cefoxitin, and imipenem. Only one strain (S158B) was resistant to both teicoplanin and cefazolin. On the other hand, the presence of vanA and mecA genes was not detected in the strains. Pulsed-field gel electrophoresis analysis was used to identify genetic-relatedness of the MDR strains. It is noteworthy that some strains from different sources showed 100% homology; however, some of MDR strains were found unrelated with 60% or less homology. The high diversity observed in pulsed-field gel electrophoresis results indicated the possible contamination of S. aureus from different sources and routes.

Identification of extracellular enzyme producing thermophilic bacilli from Balcova (Agamemnon) geothermal site by ITS rDNA RFLP

Aims:  Molecular characterization of extracellular enzyme producing thermophilic bacilli from Balcova geothermal site.

Identification of extracellular enzyme producing alkalophilic bacilli from Izmir province by 16S‐ITS rDNA RFLP

Aims:  To screen industrially important extracellular enzymes from the newly isolated alkalophilic bacilli and to characterize them by phenotypic and 16S‐internal transcribed spacer (ITS) rDNA restriction pattern analysis.

Isolation and characterization of Bacillus thuringiensis strains from olive‐related habitats in Turkey

Aims:  To isolate Bacillus thuringiensis strains from different olive‐related habitats (olive groves and olive oil factories) in Turkey and to characterize these strains by molecular methods.

Production of Food Grade β-Galactosidase from Artisanal Yogurt Strains

Superior artisanal isolates of thermophilic lactic acid bacteria producing high lactic acid and β-galactosidase were isolated from traditional Turkish yogurt samples from the Toros mountain region from a highly bio-diverse environment. A full factorial statistical design, with the factors of types of strains and medium formulations under static and agitation conditions, were applied to investigate the effects on β-galactosidase and lactic acid production. Streptococcus thermophilus 95/2 and Lactobacillus delbrueckii subsp. thermophilus 77 exhibited remarkable potential as promising starter culture candidates valuable to various applications in the dairy industry. The efficiency of cell disruption methods was investigated on the extraction of intracellular β-galactosidase enzyme. Lysozyme enzyme treatment was determined as the most effective method, which resulted in approximately 1.5 and 10 times higher enzyme activity than glass bead and homogenization treatment, respectively.

Chromatographic separation of amyloglucosidase from the mixtures of enzymes

Abstract An affinity chromatographic separation of amyloglucosidase (AMG) enzyme using β-cyclodextrin-chitosan matrix was investigated in this study. The adsorbent selectively adsorbed AMG from the mixtures of enzymes (lactase and α-amylase), and this selectively bound AMG was eluted from the column in two steps with a recovery yield of about 72%. A small fraction of AMG and other contaminating proteins did not bind to the column specifically and were eluted easily. Purified AMG was visualised on the sodiumdodecyl sulphate–polyacrylamide gel electrophoresis (SDS–PAGE) experiments.

Microencapsulation of L. acidophilus NRRL B-4495 in whey Protein-Pullulan Microparticles: Influence of Pullulan Concentration and Outlet Temperature

Spray drying technique is one of the oldest methods adapted to many industrial areas to protect bioactive components. In this study, pH and heat tolerance of encapsulated probiotic Lactobacillus acidophilus NRRL B-4495 cells were investigated. Additionally, influence of process conditions including outlet temperature and pullulan concentration on spray drying process was observed. Scanning electron microscopy images showed that incorporation of pullulan higher than 2.0 % in wall matrix created huge amount of fibrous particles. Spherical microcapsules having smooth surface were formed with 2.0 % pullulan (WPI-pullulan 4.5:1 )formulation leading to an improvement of barrier properties of microcapsules. Moreover, incorporation of pullulan improved the survival rate to 94.21 % after spray drying. Results suggested that decreasing outlet temperature exhibited much higher cell survivals up to 92.68 %. However, between outlet temperatures, significant differences (p≤0.05) in moisture content and recovery of final product indicated that more effective encapsulation of L. acidophilus NRRL B-4495 cells was achieved at 50 °C. During spray drying, due to dehydration and high heat, cytoplasmic membrane of bacterial cells undergo damage and therefore, microencapsulation in WPI-pullulan blend by spray drying provided the highest survival against heat stress at 45 ÂoC. Moreover results showed that encapsulated cells survived at minimum desired level (7 log CFU/g) at pH 2.0 in contrast to free cells.