Biomedical subjects

U Bencivenga

Publications and source records attributed to U Bencivenga.

11 recordsLinked to original sources

PubMed2005

Modulation of the catalytic activity of free and immobilized peroxidase by extremely low frequency electromagnetic fields: dependence on frequency.

A study of the influence of electromagnetic fields (EMF) of various frequencies, from 50 up to 400 Hz, on the catalytic activity of soluble and insoluble horseradish peroxidase (POD) was carried out. To simulate the conditions in which the enzyme operates in vivo, the POD was immobilized by entrapment on a gelatin membrane or by covalent attachment on a nylon graft membrane. The rate of inactivation of the soluble POD was found to exhibit positive and negative interactions with the 1 mT applied magnetic field, with an optimum positive effect at 130 Hz. The immobilized PODs, on the contrary, do not exhibit negative interactions, but show a maximum positive interaction at 150 Hz when entrapped and at 170 Hz when covalently attached. At 50 Hz and at frequencies higher than 250 Hz no effects were observed with insoluble POD. The optimum frequency of positive interaction between the EMF and the catalytic activity of the insoluble enzymes is shifted with respect to that of the soluble enzymes towards higher frequencies, the size of the shifts being dependent on the intensity of the physical forces involved in the immobilization process.

Catalysis↗

PubMed2003

In vitro studies of the influence of ELF electromagnetic fields on the activity of soluble and insoluble peroxidase.

The influence of an extremely low frequency (ELF) magnetic field (50 Hz and 1 mT, EMF) on the activity of a soluble and insoluble horseradish peroxidase (E.C. 1.11.17) has been studied as a function of time. Insoluble derivatives were obtained by enzyme entrapment into two different gelatin membranes or by covalent attachment of the enzyme on two nylon membranes, differently preactivated. Results have shown that the field affects the inactivation rate of the soluble enzyme, while no effects are observed with insoluble derivatives. Since in vivo enzymes are immobilised into the biomembrane bilayer or entrapped into the cytoplasmic mixture, one might speculate that our experimental conditions do not reflect the catalytic activity of the enzymes in vivo.

Benzothiazoles↗

PubMed2002

Advantages of using non-isothermal bioreactors for the enzymatic synthesis of antibiotics: the penicillin G acylase as enzyme model.

A new hydrophobic and catalytic membrane was prepared by immobilizing Penicillin G acylase (PGA, EC.3.5.1.11) from E. coli on a nylon membrane, chemically grafted with butylmethacrylate (BMA). Hexamethylenediamine (HMDA) and glutaraldehyde (Glu) were used as a spacer and coupling agent, respectively. PGA was used for the enzymatic synthesis of cephalexin, using D(-)-phenylglycine methyl ester (PGME) and 7-amino-3-deacetoxycephalosporanic acid (7-ADCA) as substrates. Several factors affecting this reaction, such as pH, temperature, and concentrations of substrates were investigated. The results indicated good enzyme-binding efficiency of the pre-treated membrane, and an increased stability of the immobilized PGA towards pH and temperature. Calculation of the activation energies showed that cephalexin production by the immobilized biocatalyst was limited by diffusion, resulting in a decrease of enzyme activity and substrate affinity. Temperature gradients were employed as a way to reduce the effects of diffusion limitation. Cephalexin was found to linearly increase with the applied temperature gradient. A temperature difference of about 3 degrees C across the catalytic membrane resulted into a cephalexin synthesis increase of 100% with a 50% reduction of the production times. The advantage of using non-isothermal bioreactors in biotechnological processes, including pharmaceutical applications, is also discussed.

Anti-Bacterial Agents↗

PubMed2002

The alpha1-antitrypsin/elastase complex as an experimental model for hemodialysis in acute catabolic renal failure, extracorporeal blood circulation and cardiocirculatory bypass.

A modified polyethersulphone graft membrane was loaded with antiproteases, with the aim of reducing the active protease blood concentration during hemodialysis in acute catabolic renal failure or cardiopulmonary bypass. As protease/antiprotease system, elastase and alpha1-antitrypsin were used. The concentration of active elastase in aqueous solutions decreased as function of contact time with the membrane, approaching saturation. A 40% loss of elastase activity was obtained at pH 7.4, which was not due to autolysis, which accounted for 5% of the loss. The highest reduction was achieved at pH 9.0 (25% higher than at pH 7.4). The saturation level of elastase decrease, calculated by means of the Einstein equation, was reached after more than 47 minutes. We speculate that a time reduction might be achieved either increasing the concentration of immobilized antiproteases, or increasing the rate of elastase movement across the membranes by hydraulic, osmotic, or temperature gradients. This technology can be applied to hemodialysis, and in extracorporeal blood circulation to promote elastase release.

Acute Kidney Injury↗

PubMed2001

Isothermal and non-isothermal characterization of catalytic nylon membranes chemically grafted: dependence on the grafting percentage.

The behaviour of five different hydrophobic beta-galactosidase derivatives, obtained by grafting different amount of butylmethacrylate (BMA) on planar nylon membranes, has been studied under isothermal and non-isothermal conditions.Under isothermal conditions the effect of the grafting percentage on the enzyme activity has been studied as a function of pH, temperature and substrate concentration. Independently from the parameters under observation, the yield of the catalytic process reaches the maximum value at a grafting percentage value equal to 21%. The apparent K(m) values result linearly increasing with the increase of the grafting percentage, while the apparent V(max) exhibits a maximum value.Under non-isothermal conditions, a decrease of the apparent K(m) values and increase of the apparent V(max) has been found in respect to the same values obtained under isothermal conditions.The percentage activity increases induced by the presence of a temperature gradient have been found to decrease with the increase of the percentage of graft BMA.A parameter correlating the percentage increase of enzyme activity under non-isothermal conditions with the hydrophobicity of the catalytic membrane has also been identified. This parameter is the ratio between thermoosmotic and hydraulic permeability.Results have been discussed in terms of reduction of diffusion limitations for substrate and products movement towards or away from the catalytic site by the process of thermodialysis.The usefulness of using non-isothermal bioreactors in industrial biotechnological processes has been confirmed.

Journal Article↗

PubMed2000

Glucose determination by means of a new reactor/sensor system operating under non-isothermal conditions.

The dynamic and steady-state responses as well as the response times of a glucose biosensor have been studied under isothermal and non-isothermal conditions as a function of analyte concentration. The presence of a temperature gradient across the catalytic membrane system improved the biosensor characteristics, because the dynamic and steady-state responses increased and the response times decreased under non-isothermal conditions. For example, a macroscopic temperature difference of 20 degrees C applied across the catalytic membrane system increases the biosensor sensitivity of 70% and reduces of 50% its response time. The dependence of the observed effects on the magnitude of the temperature difference applied has been correlated with the substrate (and products) transport across the catalytic membrane system due to the process of thermodialysis.

Journal Article↗

PubMed1999

A glucose biosensor operating under non-isothermal conditions: the dynamic response.

The results obtained with a glucose biosensor operating under non-isothermal conditions are presented and discussed. Glucose oxidase, immobilized onto Nylon membranes, was used as biological element. An amperometric two electrodes system was employed to measure the anodic current produced by oxidation of hydrogen peroxide. Non-isothermal conditions were characterised in terms of the temperature difference, delta T = Tw - Tc, and of the average temperature of the system, Tav = (Tw + Tc)/2, Tw and Tc being the temperature in the warm and cold half-cells constituting the biosensor. Comparison between the functioning of the biosensor under isothermal and non-isothermal conditions was performed. It was found that, under non-isothermal conditions, the dynamic response and sensitivity increased, while the response times and the detection limit decreased, if comparison was done with the same parameters measured under isothermal conditions. The increase of the dynamic response was found to be proportional to the applied temperature gradient.

Biosensing Techniques↗

PubMed1998

Advantages in using immobilized thermophilic beta-glycosidase in nonisothermal bioreactors.

Catalytic membranes, obtained by immobilizing thermophilic beta-glycosidase onto nylon supports, were used in a nonisothermal bioreactor to study the effect of temperature gradients on the rate of enzyme reaction. Two experimental approaches were carried out to explain the molecular mechanisms by which the temperature gradients affect enzyme activity. The results showed that the thermophilic enzyme behaved as the mesophilic beta-galactosidase, exhibiting an activity increase which was linearly proportional to the transmembrane temperature difference. The efficiency of the system proposed was determined by calculating two constants, alpha and beta, which represent respectively the percentage increase of enzyme activity when a temperature difference of 1 degrees C or a temperature gradient of 1 degrees C cm-1 were applied across the catalytic membrane. The increase of enzyme activity in nonisothermal bioreactors entailed a proportional reduction of production times. The advantages in using thermophilic enzymes immobilized in nonisothermal bioreactors are also discussed.

Bioreactors↗

PubMed1996

A non-isothermal bioreactor utilizing immobilized baker's-yeast cells: a study of the effect on invertase activity.

The behaviour of the enzyme invertase, located on the cell wall of baker's-yeast cells and entrapped in a gelatin membrane, was studied under isothermal and non-isothermal conditions. The reaction rate linearly increased with the applied transmembrane temperature gradient, with reference either to the average temperature or to the temperature on the warm side of the catalytic membrane. These results were obtained both when the bioreactor was operated under conditions of closed volumes and when the substrate-containing solutions are recirculated. The mathematical relationships have been elaborated between the temperatures read in the working solutions and those on the two faces of the catalytic membrane. Since the temperature difference across the membrane is smaller than that indicated by the thermocouples, the observed effects are greater than expected. The potential advantages of the use of a non-isothermal bioreactor in processes of industrial interest are discussed.

Biotechnology↗

PubMed1987

Temperature gradients and prebiological evolution.

Thermodiffusive transport of trace elements that play important roles in living organisms, such as molybdenum, nickel, copper, and vanadium, was studied in a nonisothermal biphasic system comprised of a liquid solution and jelly layers. Our intent was to mimic the effects of temperature gradients on prebiological evolution. Conditions were found, similar to those probably existing during development of early eobionts, under which all the elements tested were concentrated within the heated jelly. Nonisothermal matter transport through grossly porous artificial membranes--the process of thermodialysis--was next investigated to assess the behavior of compartmentalized, i.e., membrane bound, eobionts. Particular interest was dedicated to the continuity of nonisothermal transport phenomena in the homogeneous and heterogeneous (membrane) systems and to the ability of compartmentalized eobionts to withstand osmotic swelling by means of thermoosmotic transport. Interestingly enough, under the experimental conditions adopted, sodium/potassium countertransport is also found, suggesting a very early physicochemical origin of the sodium-potassium pump. Surprisingly enough, evidence of teleonomic behavior appears in those very simple analogs of prebiological systems.

Biological Evolution↗

PubMedDate not supplied

Increase in beta-galactosidase activity in a non-isothermal bioreactor utilizing immobilized cells of Kluyveromyces fragilis: fundamentals and applications.

The beta-galactosidase activity of Kluyveromyces fragilis cells immobilized in a kappa carrageenan gel was studied in a bioreactor functioning under isothermal and non-isothermal conditions. We observed an increase in enzyme activity which was found to be proportional to the intensity of the temperature gradient applied across the biocatalytic membrane, as well as to the average temperature of the bioreactor. The efficiency of such a non-isothermal bioreactor was calculated with respect to the yield of a bioreactor working under comparable isothermal conditions and was evaluated in terms of reduction of processing times in industrial applications. The possibility that enzyme activity in living cells is affected by non-isothermal conditions naturally existing owing to metabolic heat production is also discussed.

Bioreactors↗