Kısmi saflaştırılmış salatalık (Cucumis sativus L.) askorbat oksidazının aktivite tayini için yeni bir titrimetrik yöntem

The determination of L-ascorbic acid (Vitamin C) in various foodstuffs, soft drinks, fruit and vegetables, vitamin tablets and rarely in physiological fluids is of great importance. Nowadays, L-ascorbic acid is widely used as an additive and antioxidant for foodstuffs. Consequently, extensive investigations about Vitamin-C determination have been succeeded. Recent studies have been concentrated on the enzymatic methods in which ascorbate oxidase has been used in order to develop a special method for L-ascorbic acid in the presence of interfering substances. In this work, ascorbate oxidase, which will later be used for the purposes mentioned above, was isolated from cucumber (Cucumis sativus L.) by developing an economic and practical method. The partially purification of ascorbate oxidase was carried out and a new titrimetric method has been developed by the modification of DCIP method, used for L-ascorbic acid analyses to determine the activity of ascorbate oxidase.Çeşitli gıdalarda, meyve sularında, meyve ve sebzelerde, vitamin tabletlerinde ve bazen de fizyolojik sıvılarda L-askorbik asit (C-vitamini) tayini büyük önem taşımaktadır. Günümüzde L-askorbik asit yaygın bir şekilde gıda maddelerine katkı maddesi ve antioksidan olarak ilave edilmektedir. Özellikle bu durum C-vitamininin tayini üzerinde kapsamlı çalışmalar yapılmasına neden olmaktadır. Son yıllardaki çalışmalar L-askorbik asidi girişim etkilerinden etkilenmeksizin spesifik bir şekilde tayin etmek için, askorbat oksidazın kullanıldığı enzimatik yöntemler üzerinde yoğunlaşmaktadır. Bu çalışmada, yukarıda sözü edilen amaç çerçevesinde kullanılacak askorbat oksidazın (EC 1.10.3.3) salatalıktan (Cucumis sativus L.) pratik ve ekonomik bir şekilde izolasyon ve kısmi saflaştırılması gerçekleştirildi. Kısmi saflaştırılmış askorbat oksidaz aktivitesinin tayini için L-askorbik asit tayininde kullanılan DCIP yöntemi modifiye edilerek yeni bir titrimetrik yöntem geliştirildi

Sulfite determination by an inhibitor biosensor-based mushroom (Agaricus bisporus) tissue homogenate

PubMed ID: 21714707The aim of the study presented here is to develop a biosensor based on mushroom (Agaricus bisporus) tissue homogenate for sensitive and economical determination of sulfite in foods. The working principle of the biosensor is based on an inhibition effect of sulfite on polyphenol oxidases in mushroom. Mushroom tissue homogenate was immobilized by gelatin and glutaraldehyde on a Clark-type oxygen electrode. Some optimization studies related to the bioactive layer components and working conditions were identified. The biosensor was applied to the food samples. The biosensor reported here was successfully allowed to analyze sulfite, which was a food additive in real food samples. © 2012 Informa Healthcare USA, Inc

ß-Galactosidase monitoring by a biosensor based on Clark electrode: Its optimization, characterization and application

PubMed ID: 18395435ß-Galactosidase is an hydrolase enzyme that catalyzes the hydrolysis of ß-galactosides into monosaccharides. Substrates of different ß-galactosidases include ganglioside GM1, lactosylceramides, lactose, and various glycoproteins. A novel aspect of the activity determination of ß-galactosidase was presented. A glucose oxidase biosensor based on Clark electrode was utilized in order to monitor ß-galactosidase. Immobilization of glucose oxidase was made by gelatin and glutaraldehyde as cross-linker. Several parameters such as glucose oxidase activity, gelatin amount, and glutaraldehyde percentage for cross-linking were optimized. The most important parameter, lactose concentration in working buffer was studied in detail. Optimum temperature, thermal stability, optimum pH, buffer system and its concentration effect on the biosensor system, repeatability, reproducibility, and storage and operational stabilities of the biosensor were identified. A linear detection range for ß-galactosidase was observed between 9.4 × 10-5 and 3.2 × 10-2 U/ml. Finally, ß-galactosidase activity in artificial intestinal juice was investigated by the biosensor and the results obtained were compared with a reference spectrophotometric method. © 2008 Elsevier B.V. All rights reserved.Canon Foundation for Scientific Research: 2004 FEN 002The authors are grateful to the financial supports of Ege University, Scientific Research Foundation (Grant No. 2004 FEN 002). -

Direct determination of sulfite in food samples by a biosensor based on plant tissue homogenate

In the work described here, a biosensor was developed for the determination of sulfite in food. Malva vulgaris tissue homogenate containing sulfite oxidase enzyme was used as the biological material. M. vulgaris tissue homogenate was crosslinked with gelatin using glutaraldehyde and fixed on a pretreated Teflon membrane. Sulfite was enzymatically converted to sulfate in the presence of the dissolved oxygen, which was monitored amperometrically. Sulfite determination was carried out by standard curves, which were obtained by the measurement of consumed oxygen level related to sulfite concentration. Several operational parameters had been investigated: the amounts of plant tissue homogenate and gelatin, percentage of glutaraldehyde, optimum pH and temperature. Also, some characterization studies were done. There was linearity in the range between 0.2 and 1.8 mM at 35°C and pH 7.5. The results of real sample analysis obtained with the biosensor agreed well with the enzymatic reference method using spectrophotometric detection. © 2004 Elsevier B.V. All rights reserved

ß-galactosidase determination by an electrochemical biosensor mediated with ferrocene

PubMed ID: 21338333In this paper, a new viewpoint on the activity determination of ß-galactosidase is reported. Glucose oxidase was directly immobilized on a glassy carbon electrode and mediated by ferrocene. The biosensor's performance was based on mediated electron transfer by ferrocene, which reduced via glucose oxidase reaction. In this reaction, substrate of glucose oxidase, glucose was provided by the activity of ß-galactosidase in the sample. The parameters of the fabrication process for the electrode were optimized. Experimental conditions influencing the biosensor performance, such as pH, ferrocene and lactose concentrations, and temperature, were investigated and assessed. Finally, the biosensor was successfully applied to determination of ß-galactosidase activity of artificial intestinal juice. © 2011 Informa Healthcare USA, Inc.Canon Foundation for Scientific Research: 2004 FEN 002The authors wish to thank for financial support Ege. University, Scientific Research Foundation (Grant No. 2004 FEN 002), and The Scientific and Technical Research Council of T ü rkiye (TUB ITAK). Address correspondence to Mustafa Kemal S ü rk, Nam ı k Kemal University, Faculty of Arts and Science, Chemistry Department, 59100, Tekirda ^, Turkey. E-mail: [email protected] -

A biosensor for the determination of ß-galactosidase activity: A different viewpoint on biosensors

PubMed ID: 21351849ß-galactosidase splits lactose into glucose and galactose. Because of its biotechnological interest, we presented a biosensor system in order to monitor ß-galactosidase activity. Immobilization steps of the biosensor were identified by cyclic voltammograms and electrochemical impedance spectroscopy. ß-galactosidase was voltammetrically detected at about +150 mV (vs. Ag/AgCl) in citrate buffer solution (0.05 M, pH 4.8). The linear response for ß-galactosidase detection was in the range of 0.0118 U mL -1to 0.47 U mL -1and a shorter response time of ~50 s. Our results demonstrated the biosensor's electrochemical properties and analytical characteristics were very useful and effective for monitoring of ß-galactosidase activity. © 2011 Informa Healthcare USA, Inc.Canon Foundation for Scientific Research: 2004 FEN 002The authors are grateful for the financial support of Ege Univ.ersity, Scientific Research Foundation (Grant No. 2004 FEN 002) and The Scientific and Technical Research Council of T ü rkiye (TUB ITAK). Address correspondence to Mustafa Kemal Sezgint rk, Nam ı k Kemal University, Faculty of Arts and Sciences, Chemistry Department, 59100 Tekirda ^, Turkey. E-mail: [email protected] or [email protected]. -