The preparation and kinetics of immobilised penicillin amidase from Escherichia coli

The kinetics of penicillin-V deacylation on an immobilized enzyme

An immobilized Penicillin-V-acylase (commercial name, Novozym 217) with high specificity for the phenoxyacetyl-(V)- side chain was investigated in a recycle reactor and in a batch reactor to find the enzymatic reaction rate as a function of conversion, x, substrate concentration, c(A) (0) and pH. The reaction rate depends strongly on pH, and both products, phenoxy-acetic acid and 6-APA, inhibit the reaction. Nonspecific side reactions amount to only a few per cent when c(A) (0) <150 mM and pH& gt; 6.5. The effectiveness factor for commercial-size particles is found to be about 0.65, and a value of 1.3mM is obtained for the equilibrium constant, K(eq), of the deacylation reaction. A kinetic model for the deacylation process which includes the effect of pH and of the reverse (acylation) reaction is proposed. Rate data for particles of different size are fitted to the nonlinear model. Five kinetic parameters and an effective diffusivity for the immobilized enzyme particles are determined.

Biochemical engineering of biocatalysts immobilized on cellulosic materials

Complete design of the optimum immobilized biocatalyst seems to still be a matter of the future. To be successful, it would require numerical determination of all significant parameters at each enzyme engineering phase, that is at the design of the carriers, immobilized biocatalysts and immobilized reactors. Future research trends should follow this strategy. For processing, cellulosic materials have been considered carriers that fulfill requests to an example model: they represent a unique family of carriers that cover a broad variety of physical and chemical properties, immobilizing techniques, and immobilized reactors as well. The reason for writing this review article was to test the reliability of such a processing and subsequently, to confront theoretical considerations with practical applications of biocatalysts immobilized on cellulose materials.

Bioconversions in aqueous two-phase systems

Bioconversions involving enzymes and/or microbial cells in aqueous two-phase systems are reviewed. The partitioning of biocatalysts, substrates, and products is discussed in relation to their size. The efficiency of retaining biocatalysts in aqueous two-phase systems is summarized in relation to other methods of recirculating. The influence of phase components on the activity and the stability of enzymatic biocatalysts is exemplified with penicillin acylase and the cellulolytic enzyme system, and the effect of phase components on biocatalytic living cells is exemplified with the production of alpha-amylase with Bacillus sp. Process design costs in bioconversions in aqueous two-phase systems are briefly summarized.

Enzyme action in polymer and salt solutions. I. Stability of penicillin acylase in poly(ethylene glycol) and potassium phosphate solutions in relation to water activity

The stability of penicillin acylase (penicillin aminohydrolase, EC 3.5.1.11) was studied in poly(ethylene glycol) and potassium phosphate solutions. Enzyme stability measured as the half-life of the enzymatic activity and the transition temperature determined by differential scanning calorimetry, correlated well. The enzyme stability could not be related to the water activity as a measure of solute-solvent interaction. It seems to be related more to the concentration of the solutes and much less to the molecular weight of poly(ethylene glycol). The stabilizing effect of poly(ethylene glycol) is also discussed in terms of poly(ethylene glycol)-protein interactions.

Preparation and enzymatic properties of subtilisin Novo chemically attached to soluble DEAE-dextran and insoluble DEAE-sephadex

Analogous soluble and insoluble derivatives of subtilisin Novo (EC 3.4.21.14) were prepared by coupling the enzyme to CNBr-activated DEAE-dextran and DEAE-Sephadex, respectively. The DEAE-dextran-subtilisin displayed pH optima and Km values for ester hydrolysis similar to subtilisin, whereas the pH versus activity profiles obtained with DEAE-Sephadex-subtilisin were shifter towards the alkaline pH region and the Km values were increased. Compared with subtilisin, DEAE-dextran-subtilisin showed a 40-65% reduction of kcat for hydrolysis of N-acetyl-L-tyrosine ethyl ester, p-tosyl-L-arginine methyl ester and benzyloxycarbonyl-glycyl-L-tyrosinamide and its maximum velocities for digestion of casein and clupein also amounted to 40-60% of the subtilisin values. With Deae-sephadex-subtilisin, in contrast, the maximum velocity of hydrolysis decreased to a greater extent for polypeptide substrates compared to ester substrates. The present results indicate that the chemical nature of a support can effect intrinsic properties of a matrix-bound enzyme in addition to the steric and diffusional effects usually observed with polymer-attached enzymes.