Gıda İşleme Bölümü

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https://hdl.handle.net/20.500.12491/10781

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Detailed investigation on the insulation and permeability characteristics of rigid polyurethane foam loaded with micron-sized Turkey feather powder depending on the free volume change
(SAGE Publiscations Ltd, 2023) Soykan, Uğur; Çetin, Sedat; Yahşi, Uğur
This study brokes new ground to understand the insulation and permeability performances of rigid polyurethane foams (RPUFs) containing the different contents of micron-sized turkey feather powders (TFPs) depending on the free volume change for the first time. The effects of TFPs loading on the RPUFs were investigated by the examination of their structural and chemical features (particle size and ATR-FTIR analyses), free volume property (PALS analysis), insulation features (thermal conductivity and sound absorption tests), permeability performance (air and water vapor permeability tests) and cellular topology (SEM). PALS analysis results revealed that the addition of TFPs into the foams led to the sharp decrease in all free volume parameters since TFPs caused the formation of the disordered cells by occupying the holes in the matrix. Furthermore, both thermal conductivity and acoustic performance of the resulting foams get worse when compared to unfilled RPUF. This results were attributed to the formation of thinner and weaker cells during polymerization, reduction in the amount of CO2 inside the cells, enhancement in the solid-phase level in the matrix due to the increasing of volumetric density. Additionally, the foam samples with high content of TFPs showed considerably lower air and water vapor permeabilities when compared to neat RPUFs due to the dominant hydrophobic character of the keratin and reduction in the degree of vacancies in the matrix. SEM analysis also revealed that TFPs showed good compatibility with RPUF, but the distorted and irregular shaped cellular morphology was obtained at high contents.
Immobilization of alpha-amylase onto Ni2+ attached carbon felt: Investigation of kinetic parameters from potato wastewater
(Wiley-V C H Verlag Gmbh, 2023) Acet, Ömür; İnanan, Tülden; Koç, Eda Öndül; Sert, Buse; Acet, Burcu Önal; Odabaşı, Mehmet
Alpha-amylase is an important enzyme for textile, food, paper, and the pharmaceutical industrial areas. In this study, Ni2+ attached carbon felt structures with nitrogen active site (Ni2+-N-ACF) are produced. The surface morphologies of the N-ACF and Ni2+-N-ACF are investigated by means of scanning electron microscopy (SEM) analysis. Ni2+ ions binding on the N-ACFs are determined by energy dispersive X-ray (EDX) analysis and a graphite furnace atomic absorption spectrometer (AAS). The effect of pH, ionic strength, initial alpha-amylase concentration, and temperature parameters is investigated for alpha-amylase immobilization on Ni2+-N-ACF structures. In addition, pH and temperature effect on the activities of the free and the immobilized amylase, kinetic parameters, storage, and operational stabilities are made. Lastly, starch degradation in potato waste water is tested on Ni2+-N-ACF. The obtained results show that alpha-amylase immobilized Ni2+-N-ACF can be used for starch degradation on an industrial scale.
Annealing-induced modifications on structural, surface chemical bonding, and electrical characteristics of p-NiO/n-TiO2 heterostructure
(Springer, 2023) Kaya, Şenol; Soykan, Uğur; Sunkar, Mustafa; Karaboğa, Seda; Doğan, Muhsin Uğur; Terzioğlu, Rıfkı; Yıldırım, Gürcan; Terzioğlu, Cabir
The influences of annealing temperatures on the electrical characteristics of a p- NiO/n-TiO2 heterojunction diode were thoroughly investigated, taking into account changes in microstructure, morphology, and surface chemistry of the p-NiO/n-TiO2 films, which were deposited on an insulating SiO2/ Si layer. During different annealing processes, considerable stress variations were observed in the p-NiO/n-TiO2 films due to the crystalline evolution of p-NiO and n-TiO2. Notably, the crystallization of the TiO2 layer, which serves as the intermediary between the back contact materials and NiO, led to the evident formation of grain structures. As the annealing temperature increased, the surface roughness also grew from 5.4 to 8.7 nm. At an annealing temperature of 500 degrees C, the formation of a parasitic NiTiOx phase was observed, particularly at the interface between NiO and TiO2. Conversely, the study also revealed that annealing temperature played a significant role in the rectifying behavior, barrier potential, and ideality factor of the diode. Among the various annealing processes, the most favorable results were achieved after annealing at 400 degrees C. At this temperature, the diode demonstrated the lowest ideality factor of 1.89, accompanied by superior rectifying behavior and a barrier potential of 0.70 eV. The findings clearly indicate that any alterations in the surface chemistry and microstructure of the film directly impact the diode's characteristics. Thus, optimizing the annealing temperature becomes crucial for enhancing the performance of the p-NiO/n-TiO2 heterojunction diode.
Evaluation of crystallinity, thermal, mechanical and morphological features of high density polyethylene composites reinforced with crosslinked semifluorinated acrylate polymer microspheres
(SAGE Publications Ltd, 2023) Soykan, Uğur; Çetin, Sedat
This study mainly aims both to prepare well-shaped crosslinked 3,3,4,4,5,5,6,6,7,7,8,8,8 tridecafluorooctyl-4-(acrloyloxy) benzoate (ABCF13) polymer microspheres and to investigate the influences of the prepared microspheres addition on the crystallinity, thermal, mechanical and morphological features of high density polyethylene (HDPE). The suspension polymerization method was used for the production of well-defined microspheres and, the content of the microspheres varied from 1.0% to 10.0% in the composites. The characterization of crosslinked poly(ABCF13) microsphere-loaded HDPE composites were performed via powder X-ray diffraction, differential scanning calorimeter, universal mechanical (tensile and impact) testers and scanning electron microscope (SEM) techniques. According to the experimental findings, a and b unit cell parameters increased initially and reached maxima with the sample including 5.0% microsphere, which were followed by dramatic decreases, while c parameter remained relatively unchanged. Thermal analysis also showed that the melting temperature of HDPE reduced with the initial loading of the microspheres, then stayed at a plateau value of about 129 degrees C due to the formation of lattice distortions, generation of microstructural disorders and the defects in the crystal structures. The mechanical test results revealed that there existed considerable improvements in tensile strength, modulus and impact strength. The maximum tensile strength 25.66 MPa, elastic modulus 499.30 MPa and maximum absorbed energy in the impact test 26.84 kJ/m(2) (29%, 42% and 41% improvement, respectively) were achieved with the blend involving 5.0% microsphere. After the maxima, the mechanical characters depicted weakening trend as the microsphere content increased in the matrix. The SEM analyses revealed that although there existed fibrillar formations in all samples, the extensions decreased with the increase of the microsphere content. While ductile behavior was observed with the formation of long-bulky extensions at low contents, brittleness started to prevail at high contents with some short and thin fibrils.
Investigation of the relation between free volume and physico-mechanical performance in rigid polyurethane foam containing turkey feather fibers: Part 2
(SAGE PUBLICATIONS LTD, 2022) Soykan, Uğur; Khaleel, Mustafa; Çetin, Sedat; Yahşi, Uğur; Tav, Cumali
Rigid polyurethane foams (RPUFs) were modified with 0-15 wt.% turkey feather fibers (TFFs) produced from waste turkey feathers. One-shut free rising method was used for the production of TFFs-filled-RPUFs in a closed mold. The dependence of mechanical performance and water vapor permeability (WVP) feature of the final foams on TFFs loading was evaluated with free volume change. The free volume analysis was performed via Positron Annihilation Lifetime Spectroscopy (PALS), while the mechanical and WVP characteristics were determined with the use of the universal tester machines. PALS findings showed that the incorporation of TFFs with RPUF matrix caused the considerable diminishment in the free volume due to TFFs serving as a filling material and formation of strong secondary bonds between components. Moreover, tensile strength and extension of the foams decreased with the increasing of TFFs, which caused by the occurrence of noteworthy restriction on the spatial alignment and orientation capability of polyurethane chains due to the lack of sufficient free volume allowing the chains to move freely. As for the compression tests, all the TFFsloaded RPUFs depicted substantially lower performance due to TFFs interfering with the ordered organization of isocyanate domains. Moreover, impact test results showed that the addition of TFFs into RPUF matrix brought about the insufficient impact energy delocalization throughout the matrix due to the restriction on the mobility of polymer chains. Additionally,the remarkable diminishment in WVP was recorded due to the reduction in the number of vacancies and constitution of keratin composed of roundly 60% of hydrophilic protein (especially cystine). All in all, this study established a strong links between free volume and characteristics of TFFs-loaded RPUFs.
Antimicrobial and antioxidant activity of phenolic extracts from walnut (Juglans regia L.) green husk by using pressure-driven membrane process
(Springer India, 2023) Arslan, Hüdaverdi; Koç, Eda Öndül; Özay, Yasin; Canlı, Oltan; Özdemir, Sadin; Tollu, Gülşah
In this study, antioxidant (DPPH and metal chelating), DNA cleavage, biofilm, and antimicrobial properties of extracted phenol from the walnut green husk (WGH) and its different concentrate and permeate samples were evaluated. For maximum phenolic compound extraction from the WGH first, the effects of solvent type (deionized water, methanol, n-hexane, acetone, and ethanol), solvent temperature (25-75 degrees C), and extraction time (0.5-24 h) were optimized. Then to concentrate phenolic compounds a pressure-driven membrane process was used with four different membrane types. The phenol contents of the concentrate samples were found to be microfiltration (MF) concentrate 4400 mg/L, ultrafiltration (UF) concentrate 4175 mg/L, nanofiltration (NF) concentrate 8155 mg/L, and reverse osmosis (RO) concentrate 8100 mg/L. LC-MSMS was used to determine the quantification of phenolic compounds in permeate and concentrate streams. In addition, all of the concentrate samples with high phenol content showed a high antioxidant activity as 100% with MF concentrate, UF concentrate, NF concentrated and RO concentrated. Likewise, concentrate samples were found to have very high antibiofilm activity as 82.86% for NF concentrate againts S. aureus, 85.80% for NF concentrate against P. aureginosa, 80.95% for RO concentrate against S. aureus, and 83.61% for RO-concentrate against P. aureginosa. When the antimicrobial activity of the extracted phenol from WGH and its different concentrate and permeate samples were evaluated by micro dilution and disk diffusion methods, it was found that the ability of the concentrate samples to inhibit bacterial growth was much higher than permeate ones. In addition, extracted phenol from WGH and its different concentrate and permeate samples showed significant DNA nuclease activity.
Role of hemp fiber addition on thermal stability, heat insulation, air permeability and cellular structural features of rigid polyurethane foam
(Sage Publications Ltd, 2023) Soykan, Uğur; Kaya, Şenol
In this current study, rigid polyurethane foams (RPUFs) composites were prepared using different percentage (3, 6, 9 and 12%) of the hemp fibers via one-shut one-step polymerization method. The influences of the hemp fiber addition on the RPUFs were investigated meticulously by means of Fourier-transform infrared spectroscopy (FTIR), thermo gravimetric analysis (TGA), thermal conductivity measurement and scanning electron microscopy (SEM) techniques by evaluating the alternations in the chemical structures of the component, thermal stability, apparent density, insulation performance and cellular topology of the produced samples. The structural analysis revealed that there existed the strong secondary chemical bonds between the functional groups belonging to the components and, depending on that, the improvement in the thermal stability of the foam samples was recorded accompanied by the formation of the better interfacial adhesion. Furthermore, thermal conductivity values of the hemp fiber-loaded RPUFs were observed to increase regularly with the increasing of the content level of the hemp fibers. This was explained by enhancement in the bulk phase conduction level depending of the apparent density rising, reduction in CO2 concentration inside cells as well as the formation of the distorted cellular structures. The obtained air permeability results displayed that the hemp fibers incorporated successfully with RPUF structure, which provides the occurrence of the novel micro barriers and pathways limiting the passage of the air throughout the matrix. The taken scanning electron microscopy images also indicated that the cellular morphology and dimensional stability of the produced foams affected negatively by the hemp fiber addition. At high contents, the wrinkled, non-uniform and irregular cellular structures were observed with ruptured and collapsed walls and struts.
Role of free volume in mechanical behaviors of side chain lcp grafted products of high density polyethylene
(Springer, 2021) Şen, Behiye Öztürk; Çetin, Sedat; Yahşi, Uğur; Soykan, Uğur
The monomer, p-benzophenoneoxycarbonylphenyl methacrylate (BPOCPMA) the polymer of which exhibit mesomorphic behavior as side chain LCP has been graft copolymerized onto high density polyethylene (HDPE) in order to improve its properties. The PALS analysis of the products displayed that the graft copolymerization, while led to relatively small increase in the free volume size at low percentages of poly(BPOCPMA), resulted in decreases in the size and fraction of the free volume with the increase of poly(BPOCPMA) content. The graft copolymerization gave rise to remarkable improvements in the mechanical properties, especially in tensile strength and modulus, and the improvements were accompanied by the decreases in the free volume fraction. SEM analysis of the fracture surfaces of the mechanical test samples displayed a gradual transition from ductile fracture at low graft contents to brittle nature dominated at high percentages of poly(BPOCPMA). The XRD analysis showed significant expansions in the lateral dimensions (a and b parameters) of the orthorhombic unit cell in the crystalline domains of HDPE matrix, in consistence with poly(BPOCPMA) content. The grafting also gave rise to noteworthy increases in the crystalline melting temperature of the HDPE
Monitoring the ripening attributes of Turkish white cheese using miniaturized vibrational spectrometers
(ELSEVIER SCIENCE INC, 2022) Yaman, Hülya; Aykas, Didem Peren; Flores, Rafael Jimenez; Saona, Luis E. Rodriguez
Monitoring the ripening process by prevalent analytic methods is laborious, expensive, and time consuming. Our objective was to develop a rapid and simple method based on vibrational spectroscopic techniques to understand the biochemical changes occurring during the ripening process of Turkish white cheese and to generate predictive algorithms for the determination of the content of key cheese quality and ripening indicator compounds. Turkish white cheese samples were produced in a pilot plant scale and ripened for 100 d, and samples were analyzed at 20 d intervals during storage. The collected spectra (Fourier-transform infrared, Raman, and near-infrared) correlated with major composition characteristics (fat, protein, and moisture) and primary products of the ripening process and analyzed by pattern recognition to generate prediction (partial least squares regression) and classification (soft independent analysis of class analogy) models. The soft independent analysis of class analogy models classified cheese samples based on the unique biochemical changes taking place during the ripening process. partial least squares regression models showed good correlation (RPre = 0.87 to 0.98) between the predicted values by vibrational spectroscopy and the reference values, giving low standard errors of prediction (0.01 to 0.57). Portable and handheld vibrational spectroscopy units can be used as a rapid, simple, and in situ technique for monitoring the quality of cheese during aging and provide real-time tools for addressing deviations in manufacturing.
A survey on surface morphology control of cross-linked poly(N-vinylpyrrolidone polymer particle via inverse suspension polymerization
(Scientific Technical Research Council Turkey-TUBITAK, 2021) Soykan, Uğur; Çetin, Sedat
Abstract: This study mainly centers on the preparation and characterization of the cross-linked poly(NVP) microspheres by means of inverse suspension polymerization technique. The effect of the cross-linker content, the volumetric ratio of dispersed phase to suspension phase (DP/CP), agitation rate, and the reaction temperature on the characteristics of the microparticles were investigated meticulously using SEM, and the optimum preparation conditions were determined. The findings revealed that the morphological and surface properties of the obtained particles could be controlled easily by changing these parameters. Accordingly, the microparticles having the perfect spherical with smooth surface and good roundness, dumbbell-shaped, snowman besides dented, sunked and macelike appearance were obtained. At low cross-linker content, bulky, distorted and accumulated particles were detected, while more stable, well-defined, and desired microspheres were observed at high content. Furthermore, as DP/CP decreased, the microspheres tended to have collapsed, distorted and little wrinkled (buckled) and indented morphologies due to the heterogeneous shrinkages in droplets. Additionally, it was apparent that the increment in stirring rates caused systematically decrement in the size of the microspheres. At relatively higher reaction temperature, the mace-like microparticles having needle-like occurrences extending outwardly perpendicular on the surface started to appear due to the stiff character of the cross-linker.
DFT, molecular docking and drug-likeness analysis: Acrylate molecule bearing perfluorinated pendant unit
(ELSEVIER, 2021) Soykan, Uğur; Sert, Yusuf; Yıldırım, Gürcan
In this study, 2-oxo-1,1-diphenyl-2-((3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl) oxy)ethyl acrylate (ODDFA) molecule was synthesized by the condensation reaction method and the detailed characterization of ODDFA was experimentally and theoretically performed for the first time. As for the theoretical work, molecular geometry, vibrational frequencies, chemical shifts (H-1 and C-13), electrochemical properties and the molecular electrostatic potential (MEP) were investigated with density functional theory method (DFT, B3LYP) at the standard 6-311++G(d,p) level of calculation in the ground state. Moreover, molecular docking simulation and drug-likeness studies of title compound are carried out to determine the pharmacy potential for the title molecule. Bond lengths and angles, the electron engagements, conjugative effect, lone pairs of electrons and possible intra-molecular charge transfer regions regarding the most favored molecular structure of the ODDFA are discussed in detail. The obtained results show that mostly all the computations and experimental results are noted to be in a good correlation with each other. HOMOLUMO analysis also depicts that the pi-pi* conjugations are concentrated on the phenyl rings and carbonyl groups as well as ODDFA molecule possesses the kinetic chemical stability. As for the MEP examination, there exist both the nucleophilic and electrophilic reactive regions together over the surface of molecule thanks to the existence of both the polar and apolar functional groups in the molecule. Moreover, the molecular docking studies confirm that the ODDFA compound studied have the strong potential to behave as the potent inhibitor for tyrosinase with the PDE code of 5I38. Drug-likeness analysis also reveals that the molecule possesses considerable molinspiration bioactivity. (C) 2021 Elsevier B.V. All rights reserved.
The use of bacteriophage cocktails to reduce Salmonella Enteritidis in hummus
(ELSEVIER, 2022) Tayyarcan, Emine Kübra; Evran, Şefika; Akın, Pervin Arı; Soykut, Esra Acar; Boyacı, İsmail Hakkı
Salmonellosis is among the most common foodborne diseases. Despite the precautions taken at every stage of the production, several Salmonella outbreaks were associated with hummus which has started to become a popular food across the world. Phages are used for the biocontrol of food pathogens and have several benefits including being effective, specific and safe. In this study, the efficacy of two phages with three multiplicity of infection (10, 100, 1000) on the reduction of Salmonella Enteritidis in hummus during the storage at 4 degrees C and 10 degrees C was evaluated. The characterization of phages was performed by examining their host range, revealing their morphological features by using TEM, and determining replication parameters by using one-step growth and adsorption curves. After these procedures, they were applied to the hummus experimentally contaminated with S. Enteritidis. As a result, it was found that phages decreased Salmonella count by 2.30 and 3.23 log units at the end of 7-day storage at 4 degrees C and 10 degrees C, respectively. Additionally, phages did not significantly affect the texture and color of hummus. This paper has shown that phages could be used to reduce Salmonella counts in hummus without affecting the features that may influence its acceptability by the consumer.
Influences of turkey feather fiber loading on significant characteristics of rigid polyurethane foam: Thermal degradation, heat insulation, acoustic performance, air permeability and cellular structure
(Elseiver Science Ltd, 2021) Khaleel, Mustafa; Soykan, Uğur; Çetin, Sedat
This comprehensive study delves into the preparation and detailed characterization of rigid polyurethane foams (RPUFs) filled with varying content levels (3, 6, 9, 12 and 15 wt%) of turkey feather fibers (TFFs) fabricated from the waste feathers. TFFs-loaded RPUFs were successfully produced via one-shut free-rise method in a closed mold. The obtained foam samples were evaluated by the examination of their chemical structure (FTIR analysis), thermal degradation behavior (TGA analysis), insulating performance (thermal conductivity and acoustic tests), application potential (air permeability test) and cellular morphology (SEM). TGA analysis revealed that the incorporating of TFFs at low percentage provided the thermal stability to the foams since the strong chemical interactions were formed between TFFs and RPUF matrix, however, this effect was lost at higher contents. 17% improvement (from 0.0352 to 0.0291 W/m.K.) in thermal insulating performance was recorded at the foam sample containing 3% TFFs beyond which thermal conductivities of the specimens increased gradually and, reached to the relatively maximum value. This improvement can be explained by the presence of high numbers of uniform distributed closed cells from RPUFs and hollow honeycomb structure of TFFs in the foam matrix. As for the acoustic features, the TFFs-modified foams showed tend to increase their acoustic performance in almost all frequencies with the increasing of the TFFs percent, which is attributed to the consistent increment in the apparent densities of the foam and reduction in the cavities in the matrices. Additionally, in comparison with unfilled foam, the foams with 3 and 6 wt% of TFFs illustrated lower air permeability (12.6% reduction) thanks to TFFs acting as an additional micro-barriers restricting air passage in the matrices. Furthermore, the taken SEM images revealed that the cellular structures of the resulting foams were considerably influenced by TFF loadings. The uniform cell distribution without any defective shapes was seen at low TFFs contents, whereas the formation of distorted and inhomogeneous cellular structures, local TFFs accumulations accompanied by the regional phase separation were observed at high contents.
Development of turkey feather fiber-filled thermoplastic polyurethane composites: Thermal, mechanical, water-uptake, and morphological characterizations
(Sage Publications, 2022) Soykan, Uğur
This present study centers sensitively on the determination of the effect of natural turkey feather fibers (TFFs) loading on fundamental features (thermal, mechanical, water-uptake, and micro-structural) of thermoplastic polyurethane (TPU). The composites with different TFFs contents (3, 6, 9, and 12 wt.%) were fabricated by the melt blending method using the twin screw extruder and micro-injection molder. The samples were characterized by means of differential scanning calorimeter (DSC), universal mechanical (tensile and hardness) tester, water-uptake, and scanning electron microscope (SEM) techniques. The thermal analysis depicted that the melting temperatures of the soft and hard segments as well as the crystallinity degree of TPU increased consistently with the increase of TFFs loading level thanks to the formation of better close-packed TPU chains in the matrices. As for the mechanical test results, when compared neat TPU, the tensile strengths were reinforced by 26.8% and 19.7%, and the modulus increased by 6.6% and 45.1% for the composite samples including 3% and 6% of TFFs, respectively. However, drastic diminishment were observed at further contents. Additionally, TFFs loadings brought about gradual increase in the water-uptake capacities of the composites due to the increasing of the number of voids and omnipresent flaws in TPU matrices. The taken SEM images also revealed that, at low contents, there existed the enrichment of interfacial adhesion between TFFs and TPU matrix, whereas the morphological appearance of the composites get worse at high contents accompanied by the formation of micro-structural defects.
Detailed analysis on thermal, microstructural, mechanical, and morphological features of side chain liquid crystalline polymer/isotactic polypropylene graft copolymers: Effect of grafted and ungrafted polymer units
(Wiley, 2021) Şen, Behiye Öztürk; Soykan, Uğur; Çetin, Sedat
The main scope of this comprehensive study is to investigate the effects of poly(p-benzophenoneoxycarbonylphenyl acrylate), poly(BPOCPA), which presenting as only graft units or both graft and ungrafted units in the matrix, on the fundamental features of isotactic polypropylene (IPP). The graft copolymerization of BPOCPA onto IPP was performed with the aid of bulk melt polymerization at varying monomer content levels ranging from 5% to 40%. The thermal behavior, crystal quality, mechanical performance, and surface morphology of the samples were investigated by means of differential scanning calorimeter, X-ray diffractometer (XRD), universal mechanical test, and scanning electron microscope (SEM) techniques. Thermal analyses depicted that there existed the noteworthy enhancements in both crystalline melting temperatures and percent crystallinities of matrix polymers. Furthermore, according to XRD results, a and b parameters increased significantly at low percentages of the graft units, while the parameter c decreased in all products in consistence with the content. As for the mechanical characterization, the grafting led to remarkable improvements in modulus, tensile and impact strength of the products. SEM micrographs indicated that the samples were completely homogeneous without any phase separation and the products exhibited brittle nature with some ductility.
Role of percent grafting and chain length of fully fluorinated pendant units in the grafted acrylic compound on crucial characteristic properties of high density polyethylene
(Elsevier Science Sa, 2020) Soykan, Uğur
This comprehensive study paves way to investigate the effects of not only the extent of grafting but also the chain length of the perfluorinated pendant tail presenting in the three different fluoroalkyl acrylate monomers on the significant characteristic properties; namely the thermal behavior, crystal structure quality, mechanical performance and morphological structure of high density polyethylene (HDPE). The individual graft copolymerizations of the monomer onto HDPE were conducted at the content level from 5 % to 30 % via bulk-melt polymerization. The characterizations of copolymers were performed with differential scanning calorimeter (DSC), powder X-ray diffractometer, universal testing machine and scanning electron microscope (SEM) techniques. As for the results deduced from DSC analysis, both the melting temperatures of HDPE and degree of crystallinity were found to increase systematically with the enhancement in the percent grafting level up to 10 % beyond which the parameters were noted to decrease drastically and reach towards globally minimum values. According to the XRD results, as the percentage of grafting enhanced, the remarkable expansions were observed in unit cell parameters of HDPE crystallized in the orthorhombic symmetry. Moreover, the presence of relatively higher amount of -CF2 groups in the perfluorinated pendant tail caused the formation of three-dimensional lateral repulsions due to its helix structure. Furthermore, there seemed to remarkably improve in the mechanical performance features in case of percent grafting level of 70.6 % where the tensile strength, Modulus and impact strength parameters were measured to be about 42.51 MPa, 539.90 MPa and 41.11 kj/m(2), respectively. These reinforcements were found to be explained by the improvement in the regulation, orientations, alignments of HDPE chains. Furthermore, the formation of thick, bulky and long-fibrils were observed at high percent grafting.
SERS-based rapid assay for sensitive detection of Group A Streptococcus by evaluation of the swab sampling technique
(Royal Soc Chemistry, 2019) Eryılmaz, Merve; Soykut, Esra Acar; Çetin, Demet; Boyacı, İsmail Hakkı; Suludere, Zekiye; Tamer, Uğur
Beta-hemolytic, Group A Streptococcus pyogenes (GAS) is a life-threating pathogen and the reason for prominent disease, pharyngitis. The conventional analysis of GAS, gold standard, takes 48 hours and the related rapid tests lack in accuracy and sensitivity. In this study, firstly, the efficiency of swab sampling, which is a must in the GAS detection, was discussed with the proposed surface-enhanced Raman spectroscopy (SERS)-based batch assay and each step was controlled by the plate-counting method. Secondly, SERS-based lateral flow immunoassay (LFIA) test strips were constructed and the variation in the SERS intensity of 5,5'-dithiobis (2-nitrobenzoic acid) (DTNB) was observed. Thus, a linear correlation was found with a R-2 value of 0.9926 and the LOD was calculated to be 0.2 CFU mL(-1) of GAS which could be counted as one cell. The combination of the gold standard with the LFIA-SERS technique enabled the fast and accurate pathogen detection. In addition, GAS was quantified with paper-based test strips up to 100 CFU ml(-1) level of bacteria for the first time without any interference. Besides, this study was featured with the discussion of the whole cell and pretreated cell detection of pathogens with LFIAs. Therefore, this work enlightens the points that have never been discussed on pathogen detection with paper-based platforms.
Investigation of different interactions between Staphylococcus aureus phages and pomegranate peel, grape seed, and black cumin extracts
(Wiley, 2019) Tayyarcan, Emine Kübra; Soykut, Esra Acar; Yılmaz, Özay Menteş; Boyacı, İsmail Hakkı; Khaaladi, Maha; Fattouch, Sarni
Today, antibiotic resistance is one of the most crucial problems so that researchers have begun to search for alternatives to antibiotics. Among these alternatives, phage therapy and phytotherapy became prominent. The present study aims to put forward a different approach by combining these two methods. For this purpose, Staphylococcus aureus phages were isolated from commercial mixtures. After that, extraction of phenolic compounds from pomegranate peels (Ps), grape seeds (GSs), and black cumin (NS) was carried out and antimicrobial activities were determined. Phage-phenolic interactions were investigated by examining the effect of phenolic extracts on phage plaque sizes and then on phage titer and bacteria count. As a result, it was found that only the NS extract had a positive effect on phage activity and increased the size of phage plaques. However, no synergistic effect was observed in experiments performed in liquid media. It was also found that P and GS extracts inhibited phage activity. Practical Applications The present study was focused on effects of extracts obtained from pomegranate peel, grape seed, and black cumin on Staphylococcus aureus phage activity. It is known that antibiotic resistance constitutes a major obstacle to the pathogen elimination. In this study, phage therapy and phytotherapy, which are prominent methods in pathogen elimination, have been combined and the effect of phenolic compounds isolated from natural sources on phage activity and bacteria count have been examined. Given the results of the current study, it has been demonstrated that the combined use of phages and antimicrobial compounds could be an important alternative to combating pathogens. It is thought that this combined method should be taken into consideration both in the practice of phage therapy on humans and animals, and in applications in the food industry.
Microencapsulation of phages to analyze their demeanor in physiological conditions
(Springer, 2019) Soykut, Esra Acar; Tayyarcan, Emine Kübra; Evran, Şefika; Boyacı, İsmail Hakkı; Çakır, İbrahim
Nowadays, phage therapy emerges as one of the alternative solutions to the problems arising from antibiotic resistance in pathogenic bacteria. Although phage therapy has been successfully applied both in vitro and in vivo, one of the biggest concerns in this regard is the stability of phages in body environment. Within the scope of this study, microencapsulation technology was used to increase the resistance of phages to physiological conditions, and the resulting microcapsules were tested in environments simulating body conditions. For this purpose, Bacillus subtilis, Salmonella enterica subsp. enterica serovar Enteritidis (Salmonella Enteritidis), and Salmonella enterica subsp. enterica serovar Typhimurium (Salmonella Typhimurium) phages were isolated from different sources and then microencapsulated with 1.33%(w/v) sodiumalginate using a spray dryer to minimize the damage of physiological environment. Stability of microcapsules in simulated gastric fluid and bile salt presence was tested. As a consequence, the maximum titer decrease of microencapsulated phages after 2-h incubation was found to be 2.29 log unit for B. subtilis phages, 1.71 log unit for S. Enteritidis phages, and 0.60 log unit for S. Typhimurium phages, while free phages lost their viability even after a 15-min incubation. Similarly, microencapsulation was found to increase the stability of phages in the bile salt medium and it was seen that after 3 h of incubation, the difference between the titers of microencapsulated phages and free phages could reach up to 3 log unit.
In vitro properties of potential probiotic indigenous lactic acid bacteria originating from traditional pickles
(Hindawi Ltd, 2015) Tokatlı, Mehmet; Gülgör, Gökşen; Elmacı, Simel Bağder; İşleyen, Nurdan Arslankoz; Özçelik, Filiz
The suitable properties of potential probiotic lactic acid bacteria (LAB) strains (preselected among 153 strains on the basis of their potential technological properties) isolated from traditional Cubuk pickles were examined in vitro. For this purpose, these strains (21 Lactobacillus plantarum, 11 Pediococcus ethanolidurans, and 7 Lactobacillus brevis) were tested for the ability to survive at pH2.5, resistance to bile salts, viability in the presence of pepsin-pancreatin, ability to deconjugate bile salts, cholesterol assimilation, and surface hydrophobicity properties. Most of the properties tested could be assumed to be strain-dependent. However, Lactobacillus plantarum and Lactobacillus brevis species were found to possess desirable probiotic properties to a greater extent compared to Pediococcus ethanolidurans. In contrast to Pediococcus ethanolidurans strains, the tested Lactobacillus plantarum and Lactobacillus brevis strains exhibited bile salt tolerance, albeit to different extent. All tested strains showed less resistance to intestinal conditions than gastric juice environment. Based on the survival under gastrointestinal conditions, 22 of the 39 strains were selected for further characterization. The eight strains having the highest cholesterol assimilation and surface hydrophobicity ratios could be taken as promising probiotic candidates for further in vivo studies, because of the strongest variations found among the tested strains with regard to these properties.

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