Nurdan Kasikara Pazarlioglu

Detection of phenolic compounds by thick film sensors based on Pseudomonas putida.

Amperometric biosensors using bacterial cells were developed for the determination of phenolic compounds and the measurement was based on the respiratory activity of the cells. For this purpose, Pseudomonas putida DSM 50026 which is one of the well-known phenol degrading organisms, was used as a biological component. The cells were grown in the presence of phenol as the sole source of organic carbon. As well as phenol adapted cells, the bacterium which used the glucose as the major carbon source, was also used to obtain another type of biosensor for the comparison of the responses and specificities towards different xenobiotics. The commercial oxygen electrode was used as a transducer to test the sensor responses for both induced and non-induced cells. Our results showed that the adaptation step enable us to obtain biosensor devices with different substrate specificity. Moreover, P. putida was immobilized on the surface of thick film working electrodes made of gold by using gelatin membrane cross-linked with glutaraldehyde. The biosensors were calibrated for different phenolic substances. Furthermore, phenol detection was performed in synthetic wastewater samples.

Screening for ligninolytic enzymes from autochthonous fungi and applications for decolorization of Remazole Marine Blue

This study presents new and alternative fungal strains for the production of ligninolytic enzymes which have great potential to use in industrial and biotechnological processes. Thirty autochthonous fungal strains were harvested from Bornova-Izmir in Turkiye. In the fresh fruitbody extracts laccase, manganese peroxidase and lignin peroxidase activities, which are the principal enzymes responsible for ligninocellulose degradation by Basidiomycetes, were screened. Spores of some of the basidiomycetes species such as Cortinarius sp., Trametes versicolor, Pleurotus ostreatus, Abortiporus biennis, Lyophyllum subglobisporium, Ramaria stricta, Ganoderma carnosum, Lactarius delicious ve Lepista nuda were isolated and investigated optimum cultivation conditions in submerged fermentation for high yields of ligninolytic enzyme production. In addition, isolated fungal strains were monitored on agar plates whether having the capability of decolorization of a textile dye Remazol Marine Blue.

Determination of phenolic acids using Trametes versicolor laccase

Two biosensors based on Trametes versicolor laccase (TvL) were developed for the determination of phenolic compounds. Commercial oxygen electrode and ferrocene-modified screen-printed graphite electrodes were used for preparation of laccase biosensors. The systems were calibrated for three phenolic acids. Linearity was obtained in the concentration range 0.1-1.0muM caffeic acid, 0.05-0.2muM ferulic acid, 2.0-14.0muM syringic acid for laccase immobilised on a commercial oxygen electrode and 2.0-30.0muM caffeic acid, 2.0-10.0muM ferulic acid, 4.0-30.0muM syringic acid for laccase immobilised on ferrocene-modified screen-printed electrodes. Furthermore, optimal pH, temperature and thermal stability studies were performed with the commercial oxygen electrode. Both electrodes were used for determination of a class of phenolic acids, achieving a cheap and fast tool and an easy to be used procedure for screening real samples of human plasma.

Enhanced production of manganese peroxidase by Phanerochaete chrysosporium

Production of manganese-dependent peroxidase (MnP) by the white-rot fungus Phanerochaete chrysosporium BKM-F-1767 (ATCC 24725) was monitored during growth in different media and growth conditions. The effect of some activators of MnP production, Mn2+, Tween 80, phenylmethylsulphonylfloride (PMSF), oxygen, temperature, pH, glycerol and nitrogen was studied. Supplementing the cultures with Tween 80 (0.05 %, v/v) and Mn2+ (174 µM) resulted a maximum MnP activity of 356 U/L which was approximately two times higher than that obtained in the control culture (without Tween 80). Decolourisation of Direct Blue 15 and Direct Green 6 (50 mg/L) was also achieved with MnP.

Biodegradation of Direct Blue 15 by free and immobilized Trametes versicolor.

To investigate biodegradability by Trametes versicolor, five structurally different direct azo-dyes--Direct Black 38, Direct Blue 15 (DB 15), Direct Orange 26, Direct Green 6, and Direct Yellow 12--were studied. The DB 15 was determined as the best biodegradable dye by this white-rot fungus. Laccase and manganese peroxidase activities were monitored with the biodegradation process; it was observed that laccase played an important role in the dye degradation, while manganese peroxidase activity could not be detected. Possible degradation products also were examined by gas chromatography-mass spectrometry, but no metabolite was detected after the degradation and/or decolorization process. To enhance performance of the fungi during the degradation, Trametes versicolor cells were immobilized in alginate beads. Then, DB 15 decolorization by immobilized Trametes versicolor was studied in a small-scale packed-bed reactor. The color removal efficiency in repeated batches was found to be 98 and 93% for 50 mg/L DB 15.

New and different lignocellulosic materials from Turkey for laccase and manganese peroxidase production by Trametes versicolor

In the present study, the production of laccase (Lac) and manganese‐dependent peroxidase (MnP) by the white‐rot fungus Trametes versicolor grown in submerged cultures with different agricultural residues was investigated. The lignocellulosic materials studied were almond shells, hazelnut husks, sunflower stems, clover straw and hazelnut cobs, because they are common agricultural wastes in Turkey. Among the different lignocellulosic materials studied, hazelnut cobs provided the highest Lac and MnP activities (47.09 and 109.21 U/L, respectively). The optimum conditions were determined for Lac and MnP production in submerged cultures of T. versicolor by using hazelnut cobs as substrate. For Lac production, the optimum incubation time, hazelnut cob concentration, pH, and shaking rate were found as 4 days, 2% w/v, 6.0 and 130 rpm, respectively. For MnP production, the optimum incubation time, hazelnut cob concentration, pH and shaking rate were found as 5 days, 2% w/v, 6.0 and 90 rpm, respectively.

Effects of mediators on the laccase biosensor response in paracetamol detection

An enzyme electrode suitable for paracetamol detection was developed by immobilizing laccase on a dissolved‐oxygen probe surface. The immobilization procedure was achieved by means of gelatin, which was then cross‐linked with glutaraldehyde. The measurement was based on the detection of oxygen consumption in relation to analyte oxidation. The optimum experimental conditions for the biosensor were investigated and the system was calibrated for paracetamol. Also the effects of three different mediators, namely HBT (1‐hydroxybenzotriazole), VLA [violuric acid (5‐isonitrosobarbituric acid)] and TEMPO (2,2′,6,6′‐tetramethylpiperidine‐N‐oxyl radical) were tested for the biosensors response. As a result, it was observed that HBT has a remarkable effect on the signal by providing more oxygen consumption during the enzymatic reaction. A linear relationship between sensor responses and analyte concentrations was obtained over the concentration range 2.0–15.0 μM, whereas, in the presence of the mediator HBT, this range became 0.5–3.0 μM.

Pseudomonas putida Based Amperometric Biosensors for 2,4-D Detection

Abstract Amperometric biosensors using Pseudomonas putida cells as a bioelement were developed for 2,4-dichloro phenoxy acetic acid (2,4-D). After the adaptation process of Pseudomonas putida to 2,4-D, cells were immobilized onto the screen printed graphite electrodes (SPG) as well as Clark oxygen probe by gelatin and glutaraldehyde. Optimum pH, temperature, and stability of the biosensor were investigated. Substrate specificities for various phenolic compounds were also searched. In repeatability studies, variation coefficients and standard deviations for both type of systems were calculated; SPG and Clark electrodes were calculated and results are given as a comparison of two systems. Finally, the biosensors were applied to 2,4-D determination in a real herbicide sample.

Laccase biosensors based on mercury thin film electrode

A biosensor was developed by immobilizing laccase onto mercury thin film electrode (MTFE) by means of gelatin that is then crosslinked with glutaraldehyde. Mercury thin film (MTF) was deposited onto glassy carbon electrode (GCE) and the obtained biosensor was utilized for the determination of phenolic compounds. The measurement was based on the amperometric detection of oxygen consumption in relation to analyte oxidation. The optimum experimental conditions for the biosensor were investigated and the system was calibrated for both catechol and phenol. A linear relationship between sensor responses and analyte concentrations was obtained in concentration range between 0.5 × 10−6– 5.0 × 10−6 M for catechol and 2.5 × 10−6– 2.0 × 10−6 M for phenol, respectively. Mercury thin film was also formed onto the surface of screen printed graphite electrodes and applied for the catechol detection. The linearity was observed in concentration range between 2.5 × 10−6– 3.0 × 10−5 M.

A Novel Carrier for Phanerochaete chrysosporium Immobilization

Phanerochaete chrysosporium BKMF-1767 cells were immobilized on different carriers. The optimum carrier according to adsorbed P. chrysosporium cells number (86.38%) was determined to be polystyrene foam, a novel carrier. The conditions for the immobilization of cells on polystyrene foam were optimized and determined as 50 rpm, 37°C, and 2 h. The results show that the adsorption of P. chrysosporium on polystyrene foam follows the Langmuir adsorption isotherm. High manganese peroxidase activity (421 U/L) and dry mass (4.7 g/L) were recovered from the batch mode polystyrene foam solid state fermentation system.