Preparation and characterization of polymer-coated mesoporous silica nanoparticles and their application in Subtilisin immobilization

Belma Özbek,Şule Ünal 한국화학공학회 2017 Korean Journal of Chemical Engineering Vol.34 No.7

The preparation and characterization of polymer-coated mesoporous silica nanoparticles (MSNs) and their application in Subtilisin (Alcalase®) immobilization were investigated. For the synthesis of polymer-coated MSNs, acrylic acid (AA) and chitosan (CS) mixture were blended as poly(acrylic acid) (PAA) and CS polymer layer onto MSNs via in-situ polymerization technique. Then, both uncoated MSNs and polymer-coated mesoporous silica nanoparticles (CS-PAA/MSNs) were characterized by taking into account properties such as morphologic pattern, size distribution, surface charge of the particles as well as thermogravimetric stability with SEM, TEM, Zetasizer and TGA analyses. Subtilisin was immobilized onto polymer-coated mesoporous silica nanoparticles via adsorption technique. For optimizing the enzyme immobilization process, the percent enzyme loading depending on the matrix amount, immobilization time and pH were investigated. Then, the activity values of immobilized enzyme and free enzyme were compared at various pH and temperature values. The maximum enzyme activity was achieved at pH 9.0 for both immobilized and free enzyme. Immobilized enzyme showed more stability at higher temperatures compared with free enzyme. Furthermore, the operational and storage stability of immobilized enzyme were determined. The activity of immobilized enzyme was reduced from 100% to 45.83% after five repeated uses. The storage stability of immobilized enzyme was found to be higher than that of free enzyme. The activity of immobilized enzyme was reduced from 100% to 60% after 28 days of storage time. We concluded that the polymer-coated MSNs were a suitable matrix for Subtilisin immobilization compared to uncoated MSNs.

A modelling study on hydrolysis of whey lactose and stability of β-galactosidase

Belma Özbek,Elçin Demirhan,Dilek K l ç Apar 한국화학공학회 2010 Korean Journal of Chemical Engineering Vol.27 No.2

In the present study, the effect of process conditions on whey lactose hydrolysis and enzyme inactivation were investigated. The experiments were carried out in 250 mL of 25 mM phosphate buffer solution by using β-galactosidase produced from Kluyveromyces marxianus lactis in a batch reactor system. The degree of lactose hydrolysis (%) and residual enzyme activity (%) against time were investigated versus lactose concentration, enzyme concentration,temperature and pH. The mathematical models were derived from the experimental data to show the effect of process conditions on lactose hydrolysis and residual enzyme activity (in the presence and absence of lactose). At the optimum process conditions obtained (50 g/L of lactose concentration, 1 mL/L of enzyme concentration, 37 oC of temperature and pH 6.5), 81% of lactose was hydrolyzed and enzyme lost its activity by 32%. The activation energy for hydrolysis reaction (EA) and the enzymatic inactivation energy (ED) were calculated as 52.7 kJ/mol and 96.7 kJ/mol. Mathematical models at various process conditions have been confirmed with the experimental results.

Phenolic Composition and Antimicrobial and Antioxidant Activities of Leucoagaricus leucothites (Vittad.) Wasser

Belma Aslim,Sahlan Ozturk 한국식품영양과학회 2011 Journal of medicinal food Vol.14 No.11

Leucoagaricus leucothites (Vittad.) Wasser is an edible macrofungus found limitedly in Turkey. The ethanolic extract of L. leucothites has shown strong antimicrobial activity against some foodborne and spoilage bacteria. Therefore, the phenolic composition of L. leucothites ethanolic extract was analyzed by using high-performance liquid chromatography. Catechin (288 mg/L) was found to be the major component in the extract. Antioxidant activity of the extract was evaluated by studying the scavenging ability of 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals, and chelating ability of the extract was assessed in a ferrous ion assay. The scavenging effect on DPPH radicals was 71% at 10 mg/mL, whereas the chelating effect on ferrous ions was 82% at 15 mg/mL. The total contents of phenol (3.40±0.5 mg/g), ascorbic acid (2.10±0.3 mg/g), β-carotene (0.02±0.0 mg/g), and lycopene (0.01±0.0 mg/g) in the macrofungi ethanolic extract were also determined.

Comparison of Antioxidant Capacities of Ganoderma lucidum (Curtis) P. Karst and Funalia trogii (Berk.) Bondartsev & Singer by Using Different In Vitro Methods

Hande Yegenoglu,Belma Aslim,Feyza Oke 한국식품영양과학회 2011 Journal of medicinal food Vol.14 No.5

The aim of the study was to investigate antioxidant activities of Ganoderma lucidum and Funalia trogii. Ethanol and water crude extracts from G. lucidum and F. trogii were investigated for their antioxidant capacity in some different assays, namely, the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity, metal chelating activity against ferrous ions, and plasma lipid peroxidation inhibitory. In addition, the amounts of total phenol, ascorbic acid, β-carotene, and lycopene components in the extracts were determined. Among the four mushroom extracts, G. lucidum water extract and G. lucidum ethanol extract showed the highest scavenging activity against DPPH radicals (50% inhibitory concentration = 0.055 ± 0.001 mg/mL). Total phenol was the major antioxidant component found in the mushroom extracts. These results showed that G. lucidum may be used in pharmaceutical applications because of its effective antioxidant properties.

Drying kinetics and effective moisture diffusivity of purslane undergoing microwave heat treatment

Elçin Demirhan,Belma Özbek 한국화학공학회 2010 Korean Journal of Chemical Engineering Vol.27 No.5

The effects of microwave drying on moisture content, moisture ratio, drying time and effective moisture diffusivity of purslane leaves (Portulaca oleracea L.) were investigated. By increasing the microwave output power (180-900W) and the sample amounts (25-100 g), the drying time decreased from 43 to 12.5 minutes and increased from 27 to 54 minutes, respectively. To determine the kinetic parameters, the drying data were fitted to various models based on the ratios of the differences between the initial and final moisture contents and equilibrium moisture content versus drying time. Among the models proposed, the semi-empirical Midilli et al. model gave a better fit for all drying conditions applied. By increasing the microwave output power and decreasing the sample amount, the effective moisture diffusivity values ranged from 5.913×10−11 to 1.872×10−10 m2/s and from 9.889×10−11 to 3.292×10−11 m2/s, respectively. The activation energy was calculated using an exponential expression based on the Arrhenius equation.

In Vitro Antimicrobial Effect of Satureja wiedemanniana Against Bacillus Species Isolated from Raw Meat Samples

Nihal Yucel,Belma Aslim,Hakan Özdoğan 한국식품영양과학회 2009 Journal of medicinal food Vol.12 No.4

the presence of Bacillus species. Among the meat samples analyzed, the predominant species isolated was Bacillus circulans; other Bacillus species were identified as Bacillus firmus, Bacillus lentus, Bacillus megaterium, Bacillus licheniformis, Bacillus mycoides, Bacillus sphaericus, and Bacillus cereus. Minced meat samples were more contaminated with Bacillus species than sliced beef sample. From these samples, 242 Bacillus species isolates were obtained, which were investigated for proteolytic and lipolytic activity, associated with meat spoilage. Interestingly, some Bacillus strains produced the highest values of proteolytic/lipolytic activities. Nineteen Bacillus strains were selected among the 242 isolates according to their proteolytic/lipolytic activity with a clear zone diameter of ≥6mm. The essential oil of Satureja wiedemanniana (Lalem) Velen was also tested against these 19 Bacillus species that had proteolytic and lipolytic activity. The essential oil yield obtained from the aerial parts of the plant was 0.35% (vol/wt). The inhibition zones of the essential oil obtained against all the Bacillus species were in the range of 5.0–12.0mm. The oil showed high antimicrobial activities against B. licheniformis M 6(26), M 11(16), and M 12(1) strains. B. licheniformis 12(1) showed high lipolytic activity (18.0mm). Also, B. licheniformis M 6(26) and M 11(16) showed high proteolytic activity (16.0 and 14.0mm). These results may suggest that an essential oil of S. wiedemanniana can be used as a natural preservative in meat against spoilage bacteria.

Sesame cake protein hydrolysis by alcalase: Effects of process parameters on hydrolysis, solubilisation, and enzyme inactivation

Elçin Demirhan,Belma Özbek,Dilek K l ç Apar 한국화학공학회 2011 Korean Journal of Chemical Engineering Vol.28 No.1

We investigated the effects of process parameters (substrate concentration, enzyme concentration, temperature and pH) on the hydrolysis and solubilization of sesame cake protein as well as enzyme stability. The sesame cake protein was hydrolyzed by Alcalase enzyme (a bacterial protease produced by a selected strain of Bacillus Licheniformis)that was chosen among five commercial enzymes examined. The optimum process conditions for hydrolysis and solubilization were obtained as 15 g L^(−1) substrate concentration, 3 ml L^(−1) enzyme concentration, 50 ℃ and pH 8.5. Under these conditions, the values of degree of hydrolysis and solubilization were found as 26.3% and 82.1%, respectively,and enzyme lost its activity by approx. 56% at the end of 120 min processing time. Modeling studies were performed to determine the kinetics of hydrolysis, solubilization and enzyme inactivation. The relationship between hydrolysis and solubilization was found linear for all experimental conditions examined. The inactivation energy of Alcalase at the temperature range of 45-55 ℃ was determined to be 25544 J mol^(−1).

Resveratrol-induced Depression of the Mechanical and Electrical Activities of the Rat Heart is Reversed by Glyburide: Evidence for Possible KATP Channels Activation

Mesut Buluc,Murat Ayaz,Belma Turan,Emine Demirel-Yilmaz 대한약학회 2007 Archives of Pharmacal Research Vol.30 No.5

Resveratrol, a natural phytoalexin found in wine, has been suggested to have benefits in preventing cardiovascular diseases. However, the direct effects of resveratrol on the activity of cardiac tissues and its mechanism of action have not been determined. This study examined the effects of resveratrol on the right and left atrium and left papillary muscle isolated from the rat heart. The contractile responses of the right atrium and papillary muscle and the action potential from the left atrium were recorded and the effects of resveratrol on these responses were observed. The resting force of the isolated right atrium and the peak developed force of the left papillary muscle were depressed by resveratrol (0.1 nM - 0.1 mM). Exposure to the KATP channel blocker glyburide (3 µM) prevented significantly the resveratrol-induced decrease. Resveratrol (0.1 mM) shortened the repolarization phase of action potential recorded from the left atrium and this effect of resveratrol was reversed by glyburide (3 µM). These results indicated that resveratrol depressed cardiac muscle contraction and shortened action potential duration probably due to the activation of KATP channels in the rat heart.

Mobile Robot Motion Framework Based on Enhanced Robust Panel Method

Jasmin Velagic,Lamija Vukovic,Belma Ibrahimovic 제어·로봇·시스템학회 2020 International Journal of Control, Automation, and Vol.18 No.5

This paper proposes a framework for the mobile robot motion in partially unknown static and dynamic environments. Its main part is a path planner which is based on the enhanced robust panel method (ERPM). This proposed method improves an existing panel method in order to be employed for moving obstacles represented as open polygonal chains. The robustness of the proposed method is provided due to the automatic adjustment of the potential field parameters. Therefore, the proposed path-planning strategy incorporates relevant obstacle pruning and activation window algorithms to speed up the overall navigation process. Furthermore, the modified Histogramic-In-Motion-Map (MHIMM) method is proposed to continuously update a grid-based map of the environment. The path planning and robot motion performance evaluation with respect to the sensor noise and different environments is done using various metrics. The effectiveness and robustness of the proposed motion frameworkare demonstrated through numerous realistic scenarios within ROS environment with Pioneer 3DX mobile robot.

In Vitro Antimicrobial Effect of Satureja wiedemanniana Against Bacillus Species Isolated from Raw Meat Samples

Yuce, Nihal,Aslim, Belma,Ozdogan, Hakan The Korean Society of Food Science and Nutrition 2009 Journal of medicinal food Vol.12 No.4

In this study a total of 30 raw meat samples obtained from Ankara, Turkey were screened for the presence of Bacillus species. Among the meat samples analyzed, the predominant species isolated was Bacillus circulans; other Bacillus species were identified as Bacillus firmus, Bacillus lentus, Bacillus megaterium, Bacillus licheniformis, Bacillus mycoides, Bacillus sphaericus, and Bacillus cereus. Minced meat samples were more contaminated with Bacillus species than sliced beef sample. From these samples, 242 Bacillus species isolates were obtained, which were investigated for proteolytic and lipolytic activity, associated with meat spoilage. Interestingly, some Bacillus strains produced the highest values of proteolytic/lipolytic activities. Nineteen Bacillus strains were selected among the 242 isolates according to their proteolytic/lipolytic activity with a clear zone diameter of ${\geq}6\;mm$. The essential oil of Satureja wiedemanniana (Lalem) Velen was also tested against these 19 Bacillus species that had proteolytic and lipolytic activity. The essential oil yield obtained from the aerial parts of the plant was 0.35% (vol/wt). The inhibition zones of the essential oil obtained against all the Bacillus species were in the range of 5.0.12.0 mm. The oil showed high antimicrobial activities against B. licheniformis M 6(26), M 11(16), and M 12(1) strains. B. licheniformis 12(1) showed high lipolytic activity (18.0 mm). Also, B. licheniformis M 6(26) and M 11(16) showed high proteolytic activity (16.0 and 14.0 mm). These results may suggest that an essential oil of S. wiedemanniana can be used as a natural preservative in meat against spoilage bacteria.