Immobilization of the urease on eggshell membrane and its application in biosensor.

Eggshell membrane is a natural material, essentially made up of protein fibers having flexibility in the aqueous solution and possessing gas and water permeability. It is used as a biomembrane for immobilization of urease for the development of a potentiometric urea biosensor. Eggshell membrane was treated with polyethyleneimine (PEI) to impart polycation characteristics. Urease was immobilized on the PEI treated eggshell membrane through adsorption. SEM study was carried out to observe the changes in surface morphology after immobilization. FTIR study of membrane was carried out to observe the changes in IR spectra after immobilization of enzyme. Immobilized membrane was associated with ammonium ion selective electrode. Biosensor exhibited sigmoidal responses for the urea concentration range from 0.5 to 10mM. The response time of the biosensor was 120 s. A single membrane was reused for 270 reactions without loss of activity. The urease-eggshell membranes were stable for 2 months when stored in buffer even at room temperature.

Glutaraldehyde activated eggshell membrane for immobilization of tyrosinase from Amorphophallus companulatus: application in construction of electrochemical biosensor for dopamine.

Tyrosinase from a plant source Amorphophallus companulatus was immobilized on eggshell membrane using glutaraldehyde. Among the three different approaches used for immobilization, activation of eggshell membrane by glutaraldehyde followed by enzyme adsorption on activated support could stabilize the enzyme tyrosinase and was found to be effective. K(m) and V(max) values for dopamine hydrochloride calculated from Lineweaver-Burk plot were 0.67 mM and 0.08 mM min(-1), respectively. Studies on effect of pH showed retention of more than 90% activity over a pH range 5.0-6.5. Membrane bound enzyme exhibited consistent activity in the temperature range 20-45 degrees C. Shelf life of immobilized tyrosinase system was found to be more than 6 months when stored in phosphate buffer at 4 degrees C. An electrochemical biosensor for dopamine was developed by mounting the tyrosinase immobilized eggshell membrane on the surface of glassy carbon electrode. Dopamine concentrations were determined by the direct reduction of biocatalytically liberated quinone species at -0.19 V versus Ag/AgCl (3M KCl). Linearity was observed within the range of 50-250 microM with a detection limit of 25 microM.

Uranium sorption by Pseudomonas biomass immobilized in radiation polymerized polyacrylamide bio-beads.

A Pseudomonas strain identified as a potent biosorbent of uranium (U) and thorium was immobilized in radiation-induced polyacrylamide matrix for its application in radionuclide containing wastewater treatment. The immobilized biomass exhibited a high U sorption of 202 mg g(-1) dry wt. with its optimum at pH 5.0. A good fit of experimental data to the Freundlich model suggested multilayered uranium binding with an affinity distribution among biomass metal binding sites. Scanning electron microscopy revealed a highly porous nature of the radiation-polymerized beads with bacterial cells mostly entrapped on pore walls. Energy dispersive X-ray analysis (EDXA) coupled with SEM ascertained the accumulation of uranium by the immobilized biomass without any physical damage to the cells. A significant (90%) part of biosorbed uranium was recovered using sodium bicarbonate with the immobilized biomass maintaining their U resorption capacity for multiple sorption-desorption cycles. Uranium loading and elution behavior of immobilized biomass evaluated within a continuous up-flow packed bed columnar reactor showed its effectiveness in removing uranium from low concentration (50 mg U L(-1)) followed by its recovery resulting in a 4-5-fold waste volume reduction. The data suggested the suitability of radiation polymerization in obtaining bacterial beads for metal removal and also the potential of Pseudomonas biomass in treatment of radionuclide containing waste streams.

Immobilization of catalase by entrapment of permeabilized yeast cells in hen egg white using glutaraldehyde.

An immobilized preparation of whole cell-based catalase was obtained by cross-linking the yeast cells permeabilized with toluene in hen egg white using glutaraldehyde. Optimal preparations were obtained when cross-linking was carried out for 2 h at 4 degrees C. Immobilized cells could be reused for the removal of H2O2 from milk.

A cloth strip bioreactor with immobilized glucoamylase.

Glucoamylase was immobilized on polyethylenimine (PEI)-coated cotton cloth by adsorption followed by cross-linking with 0.2% glutaraldehyde in the presence of starch. Optimal adsorption of the enzyme was seen when cloth treated with 2% PEI was contacted with the enzyme for 50 min. pH and temperature optima profiles were not changed appreciably on immobilization. However, the bound enzyme exhibited a higher thermal stability. The enzyme-bound cloth strips were used in a specially designed bioreactor for the continuous hydrolysis of starch. The reactor could be operated for over 21 days retaining about 70% of the original activity. An operational temperature of 45 degrees C was found to be optimal.

Hydrolysis of concentrated sucrose syrups by invertase immobilized on anion exchanger waste cotton thread.

Yeast invertase was immobilized on polyethyleneimine-coated cotton thread by adsorption followed by crosslinking with glutaraldehyde. The thread-bound invertase was used as an easily retrievable system for the hydrolysis of 80% w/v commercial sucrose syrups. The immobilized enzyme was stable for over 90 days to a temperature of 50 degrees C, only when stored in 80% sucrose solution. Above this temperature, inactivation of enzyme was observed. The cotton threads were used in a batch reactor for hydrolysis of sucrose in about 30 batches carried out over a period of 50 days without loss in activity. The threads could also be used in a packed bed reactor (1.51) for 97% hydrolysis of 80% sucrose syrups at 50 degrees C at a rate of about 360 kg per month for a period of 3 months.