Sibel Sungur

β-Galactosidase from Kluyveromyces lactis cell disruption and enzyme immobilization using a cellulose-gelatin carrier system

Abstract Whole cell immobilization is one of the major immobilization methods due to cost advantages. Extracellular enzyme producing cells can be immobilized directly, but intracellular enzyme producing cells should be treated first to increase cell permeability. In this work β-galactosidase-producing Kluyveromyces lactis (ATCC 8583) cells were used. Since β-galactosidase is an intracellular enzyme permeabilized dead cells were immobilized into gelatin using glutaraldehyde as cross-linker. Two chemical and one physical disruption processes were tested and the physical method was determined to be better because of the probable risk of chemical toxicity accompanied with the chemical methods. Thirty percent activity was obtained by immobilized cells relative to free disrupted cells.

Studies on immobilization of urease in gelatin by cross-linking

Urease enzyme was immobilized in photographic gelatin by chemical cross-linking using formaldehyde, glutaraldehyde and chromium (III) acetate. The effects of enzyme and cross-linker concentrations, temperature, incubation time and pH on urea hydrolysis were investigated. Effect of reuse on the activity of immobilized enzyme was also studied. Glutaraldehyde (0.004 M) was the most suitable cross-linker; relative activities within 2.5 months after 24 reuses were stable (about 78%).

Effect of chromium salts on invertase immobilization onto car☐ymethyl-cellulose-gelatine carrier system

The carboxymethylcellulose-gelatine carrier system was investigated for invertase immobilization. Chromium (III) acetate, chromium (III) sulphate and potassium chromium (III) sulphate were used as cross-linking agents. Effect of carboxymethylcellulose-gelatine ratio and cross-linker concentration on immobilized enzyme activity were analysed. Reusability of immobilized enzyme was also investigated. Maximum immobilized enzyme activities were obtained with cross-linkers chromium (III) sulphate (0.004 mol dm-3) and potassium chromium (III) sulphate (0.001 mol dm-3) for a carrier composition of carboxymethylcellulose-gelatine ratio 0.111 (w/w) as 78%.

Urease immobilization into poly(acrylamide) - gelatin gels

Abstract Urease ( EC. 3. 5. 1. 5 ) was immobilized into photographic gelatin-poly(acrylamide) gels by using chromium(III)acetate as crosslinker. The effect of crosslinker concentration , enzyme loading, pH, temperature, supports composition and reuse number on activity were studied. The suitable conditions for an operative and stable system were investigated.

Immobilization of alpha - amylase into gelatin films with various cross - linkers

Abstract This article reports the cross linking of α-amulase enzyme to gelatin by using formaldehyde, chromium (III) acetate, chromium (III) sulfate and potassium chromium (III) sulfate as hardeners. The effect of concentration of cross linkers, enzyme and gelatin on the activity of immobilized enzyme were investigated.

Development of Lactose Biosensor Based on β‐Galactosidase and Glucose Oxidase Immobilized into Gelatin

In this article, we describe the preparation of a new lactose biosensor based on electrode coating with β‐galactosidase and glucose oxidase immobilized gelatin. For this purpose, β‐galactosidase and glucose oxidase enzymes were immobilized onto gelatin by crosslinking with glutaraldehyde. Properties of the immobilized β‐galactosidase and glucose oxidase enzymes electrode have been studied. The effects of glutaraldehyde concentration, temperature and pH variations and reusability were among the subjects analyzed. Lactose biosensors were subjected to continuous repeated use in order to observe reusability and shelf life; where standard lactose and milk samples were used as substrate solutions. Continuous reuse experiments showed that most of the lactose biosensors activities were retained even after the 10th use in a period of 30 days.

Immobilization of α-amylase into photographic gelatin by chemical cross-linking

Abstract α-Amylase was immobilized into photographic gelatin by chemical cross-linking with chromium (III) acetate and chromium (III) sulphate. Cellulose triacetate film strips, enabled simple handling when coated with an α-amylase-gelatin mixture, accomplishing a high degree of durability during consecutive immersions into reaction media. The optimum conditions for pH, substrate concentration, temperature, incubation time and storing conditions of free and immobilized α-amylase were determined. The effect of use number on activity and the effect of resting on reuse number were also determined. Photographic gelatin was found to be a very efficient natural polymer, due to its extraordinary diffusion characteristics for immobilization as a carrier.

Polyester film strips coated with photographic gelatin containing immobilized invertase

Abstract Invertase was immobilized into photographic gelatin by chemical crosslinking with formaldehyde and chromium (111) acetate. Polyester film strips were coated with invertase-gelatin mixture which increased durability during consecutive immersions into reaction media. The effect of gelatin, crosslinker and enzyme concentrations on activity were studied. Enzyme leakages from immobilized invertase film strips were controlled by washing with EDTA solutions. The activities of washing solutions were measured spectrophotometrically to determine unbounded enzyme concentration. Effect of use number on activity was also determined. Percent activity of immobilized invertase was lower than that of free enzyme. The activity however retained even after 10 washings (170 minutes) followed by 9 use in 18 weeks.

Immobilization of Urease into Carboxymethylcellulose - Gelatine System

Abstract In the present work carboxymethylcellulose (CMC) and CMC-gelatin were used as carrier systems for urease immobilization. Immobilization was based on the formation of insoluble salts of CMC and gelatin with chromium(111) ions. Chromium(111) acetate (CA) and chromium(111) sulfate (CS) were used for this purpose and their effect on urease activity was investigated. The activities of immobilized urease using pure and CMC-gelatin carrier systems were compared. Urease activity was determined by using Berthelot method. Reuse number, pH, enzyme and cross linker concentrations and the incubation period were the factors taken into account in this investigation. Activity of immobilized enzymes were found to be stable for at least 2 months and 16–24 usage. Immobilization percentage obtained under optimum conditions was 40%.

Immobilization of glucose oxidase onto gelatin for biosensor construction

The properties of a glucose biosensor made by immobilization of glucose oxidase onto gelatin in a layer of electrochemically deposited polyaniline have been investigated. Glucose oxidase was immobilized within gelatin cross-links with chromium(III) acetate. The glucose oxidase biosensor was developed by forming a polyaniline-deposited electrode surface as support for the immobilized enzyme gel, in order to increase its durability. The polyaniline/gelatin/glucose oxidase biosensor has been characterized using chemical and electrochemical methods. Temperature, pH, cross-linking agent concentration, enzyme concentration, kinetic properties, reusability and the effect of electro-active compounds were among the parameters studied. The response time of the glucose oxidase biosensor is 90 s, the detection limit is below 1 mmol/dm3 and the sensor can be used 20 times within a 2-month period without losing its stability.