Şebnem Harsa

Protection of Lactobacillus acidophilus NRRL-B 4495 under in vitro gastrointestinal conditions with whey protein/pullulan microcapsules

In this research, whey protein/pullulan (WP/pullulan) microcapsules were developed in order to assess its protective effect on the viability of Lactobacillus acidophilus NRRL-B 4495 under in vitro gastrointestinal conditions. Results demonstrated that WP/pullulan microencapsulated cells exhibited significantly (p ≤ 0.05) higher resistance to simulated gastric acid and bile salt. Pullulan incorporation into protein wall matrix resulted in improved survival as compared to free cells after 3 h incubation in simulated gastric solution. Moreover WP/pullulan microcapsules were found to release over 70% of encapsulated L. acidophilus NRRL-B 4495 cells within 1 h. The effect of encapsulation during refrigerated storage was also studied. Free bacteria exhibited 3.96 log reduction while, WP/pullulan encapsulated bacteria showed 1.64 log reduction after 4 weeks of storage.

Preparation and Characterization of PolyLactide-Hydroxyapatite Biocomposites

In the present study, the preparation and characterization of polylactideHydroxyapatite(HA) composite films for biomedical applications have been studied. The effects of number of parameters such as polymer type, HA loading, surface modification and its concentration on the mechanical and microstructural properties of the composites were investigated. Poly-LLactide and 96/4 Poly(L-Lactide co D-Lactide) copolymer-HA composites containing 10-40 wt % HA particles have been prepared by solvent casting technique. The HA powder was synthesized by precipitation technique. Interfacial interactions between HA and polylactide polymer were modified to improve filler compatibility and mechanical properties of the composites by surface treatment of the HA with two different silane coupling agents; 3-aminopropyltriethoxysilane (AMPTES) and 3mercaptopropyltrimethoxysilane (MPTMS) at three different concentrations(0.5-2 wt%). Silane treatment indicated improvements in the mechanical properties of the composites compared to the untreated HA loaded polylactide composites. Tensile test results showed that the maximum improvement in the mechanical properties of the composites was obtained for PLA composites containing 1 wt% aminofunctional silane treated HA and 0.5-wt % mercaptopropyltrimethoxy silane treated HA for PDLA composites. Scanning electron microscopy studies also revealed better dispersion of silane treated HA particles in the polymer matrix. Introduction Bioabsorbable devices for load bearing applications, based on bioabsorbable polymer or composites can overcome some problems associated with metallic implants or devices applied in orthopaedics (1). These devices made of biodegradable polymers such as poly (L-lactide), poly (L-lactide co DL Lactide) copolymers are already in clinical use for the last twenty years [1-2]. Mechanical properties of these polymers gradually reduce as they degrade, allowing loads to be transferred to the bone, therefore reducing stress shield effect. Although they have many advantages over metallic implants, the major drawn back of such resorbable polymers is that they have weak mechanical properties especially for the load bearing applications [3]. Recently hydroxyapatite (HA) reinforced polylactide based composites have attracted great attention due to the favourable characteristics of HA which is expected to confer a bone bonding behaviour and to improve mechanical properties of these composites [4-5]. Many researchers have examined the preparation and characterization of hydroxyapatite/PLA composites in the last two decades [4-6]. In spite of the promising results obtained so far, nobody has studied the improvement of the interfacial interaction and adhesion between polylactide polymer and HA filler. The interaction and adhesion between filler and polymer matrix have a significant effect on the properties of the particulate filled reinforced materials, being essential to transfer the load between two phases and thus improve the mechanical properties. To improve the mechanical properties, it is necessary to render the surface of the filler and the polymer compatible, which can be achieved using several types of surface coupling agents. In the literature, there are many studies dealing with the characterization of interfaces and their influence on the mechanical Key Engineering Materials Online: 2004-05-15 ISSN: 1662-9795, Vols. 264-268, pp 1953-1956 doi:10.4028/www.scientific.net/KEM.264-268.1953

Mechanical Properties of Hydroxyapatite Composites Reinforced with Hydroxyapatite Whiskers

Abstract. Sintering and mechanical behavior of pure and hydroxyapatite (HA) whisker reinforced HA composites were investigated in this work. Pure and composite samples were prepared by using a commercial powder and whiskers prepared by molten salt synthesis. The dry-pressed samples were sintered in the 800 and 1300°C range. The effect of whisker-addition on the mechanical properties of HA was investigated through compression and hardness testing. Compressive strength and fracture strain were observed to increase by the addition of whiskers.

Nanotubular structures developed from whey-based α-lactalbumin fractions for food applications.

Whey proteins have high nutritional value providing use in dietary purposes and improvement of technological properties in processed foods. Functionality of the whey‐based α‐lactalbumin (α‐La) may be increased when assembled in the form of nanotubes, promising novel potential applications subject to investigation. The purpose of this study was to extract highly pure α‐La from whey protein isolate (WPI) and whey powder (WP) and to construct protein nanotubes from them for industrial applications. For protein fractionation, WPI was directly fed to chromatography, however, WP was first subjected to membrane filtration and the retentate fraction, whey protein concentrate (WPC), was obtained and then used for chromatographic separation. α‐La and, additionally β‐Lg, were purified at the same batches with the purities in the range of 95%–99%. After enzymatic hydrolysis, WPI‐based α‐La produced chain‐like and long nanotubules with ∼20 nm width while WPC‐based α‐La produced thinner, miscellaneous, and fibril‐like nanostructures by self‐assembly. Raman and FT‐IR spectroscopies revealed that α‐La fractions, obtained from both sources and the nanostructures, developed using both fractions have some structural differences due to conformation of secondary structure elements. Nanotube formation induced gelation and nanotubular gel network entrapped a colorant uniformly with a transparent appearance. Dairy‐based α‐La protein nanotubules could be served as alternative gelling agents and the carriers of natural colorants in various food processes.

Preparation of Ceramic Composite Membranes for Protein Separation

Proceedings of the 8th Conference and Exhibition of the European Ceramic Society; Istanbul; Turkey; 29 June 2003 through 3 July 2003

Improved viability of Lactobacillus acidophilus NRRL-B 4495 during freeze-drying in whey protein-pullulan microcapsules

Abstract In this research, pullulan was incorporated in protein-based encapsulation matrix in order to assess its cryoprotective effect on the viability of freeze-dried (FD) probiotic Lactobacillus acidophilus NRRL-B 4495. This study demonstrated that pullulan in encapsulation matrix resulted in a 90.4% survival rate as compared to 88.1% for whey protein (WPI) encapsulated cells. The protective effects of pullulan on the survival of FD-encapsulated cells in gastrointestinal conditions were compared. FD WPI-pullulan capsules retained higher survived cell numbers (7.10 log CFU/g) than those of FD WPI capsules (6.03 log CFU/g) after simulated gastric juice exposure. Additionally, use of pullulan resulted in an increased viability after bile exposure. FD-free bacteria exhibited 2.18 log CFU/g reduction, while FD WPI and FD WPI-pullulan encapsulated bacteria showed 0.95 and 0.49 log CFU/g reduction after 24 h exposure to bile solution, respectively. Morphology of the FD microcapsules was visualized by scanning electron microscopy.

Whey protein-pullulan (WP/Pullulan) polymer blend for preservation of viability of Lactobacillus acidophilus

In this study, whey protein isolate-pullulan (WP/pullulan) microspheres were developed to entrap the probiotic Lactobacillus acidophilus NRRL-B 4495 by spray-drying technique. Microcapsules were analyzed for physicochemical characteristics including morphology, particle size, moisture content, water activity, dissolution time, and color properties. Results revealed that microcapsules were spherical in shape and obtained particle sizes between 5 and 160 µm, with an average size of around 50 µm. Blending pullulan with WP provided enhanced survival of probiotic bacteria during spray drying with a final viable cell number of 8.81 log CFU/g of microcapsule. Encapsulated probiotics were also found to have significantly (p ≤ 0.05) higher survived cell numbers compared to free probiotics under detrimental gastrointestinal conditions. Moreover, dissolution analysis suggested that protein-polysaccharide powdered microcapsules showed pH-sensitive dissolution properties in simulated gastric juice and simulated intestinal juice.

Preparation and Characterization of Hydroxyapatite/Calcium Phosphate Powders

The preparation of calcium phosphate based powders through chemical precipitation in order to determine the optimum conditions for the preparation of stoichiometric, thermally stable hydroxyapatite (HA) powders was investigated in this work. The effects of parameters like pH, aging time, and heat treatment temperature on the phase structure and morphology of the powders were investigated by SEM and XRD.HA was prepared at a Ca/P ratio of 1.67. The precipitation pH had a profound influence on the morphology and crystallite size of the powders in the 4-11 pH range. Relatively large 5μm prismatic particles were obtained at low pH whereas the powders were formed from agglomerates of nano sized particles at high pH. Powders had a HA dominant phase structure above a pH of 8. Phase pure HA powders were obtained with close to theoretical yields at pH = 10 and 11. The crystallite sizes of the powders varied from about 30 nm at 90°C to 50-90 nm at 1250°C with the smallest crystallite sizes obtained for pH 10 and 11 powders at 1250°C. The crystallite size increased significantly with aging temperature. Introduction The average 70 kg man contains about 780 g P, of which about 700 g is present as bone apatite corresponding to about 3.5-4 kg hydroxyapatite [1]. Since hydroxyapatite is the main inorganic component of the hard tissues, among all materials it seems to be the most promising material for renewing and regeneration operations because of its excellent biocompatibility. Synthetic HA powder with composition Ca(10-x)(HPO4)x(PO4)(6-x) (OH)(2-x) 0 ≤ x ≤1 is commonly prepared by various precipitation techniques. The powder properties may be directly affected by various precipitation parameters lie Ca/P ratio of the starting reagents, pH, aging time and temperature, stirring, addition rate of the reactants, etc [2,3,4,5]. The preparation of HA ceramics with a fine microstructure and improved mechanical properties necessitates consolidation of nonagglomerated nano-sized particles and uniform particle size distributions. In this study the effect of pH, aging time and temperature on the powder properties like crystallite size, phase purity, morphology and thermal stability was investigated. Experimental Powders were precipitated by the drop wise (10 ml/min) addition of 0,334 M 500cc Ca(NO3)2.4H2O (Sigma) solution to 0,2 M 500cc (NH4)2HPO4 (Merck) solution. pH of the solution was adjusted by addition of NH4OH at specific pH value at 60°C while stirring. The Ca/P ratio was set at 1,667 in the final reaction medium. The precipitates was filtered and washed several times with deionised water and were further washed with ethyl alcohol to remove the excess water from the precipitate to control agglomerate strength. The precipitate oven dried at 90°C. Six different powders in the range of 4-11 were prepared by aging at 60°C for 24 hrs. The precipitate was aged at 30°C, 60°C, 90°C before filtration in order to understand the effects of aging temperature on powder properties. The aging time was varied in the 0-48 hrs for aging Key Engineering Materials Online: 2004-05-15 ISSN: 1662-9795, Vols. 264-268, pp 2075-2078 doi:10.4028/www.scientific.net/KEM.264-268.2075

Adsorption equilibrium and dynamics of lactase/CM-Sephadex system

Partitioning behaviour and adsorption isotherms of lactase/CM-Sephadex system at equilibrium were investigated together with the adsorption kinetics in this study. Maximum adsorption was obtained at the pH values between 5.5–6.0. Adsorption isotherm was a close fit to the Langmuir model.