Immobilization of cellulolytic and hemicellulolytic enzymes on inorganic supports

Commercial cellulase preparations from Trichoderma viride and Aspergillus niger were immobilized on porous silica glass and ceramics such as alumina and titania with titanium tetrachloride (TiCl(4)) and on their silanized derivatives with glutaraldehyde (GLUT). The amounts of the immobilized enzymes were in the range 10-50 mg/g carrier (dry) depending on the kind of carrier and immobilization method. Their activities toward carboxymethyl cellulose (CMC), xylan, aryl-beta-glucoside, and aryl-beta-xyloside were 3-53% of those of the native enzymes. The optimum pH of the enzymes shifted to the acidic side in most cases, whereas the optimum temperatures were nearly the same as those of native ones. The activity of immobilized enzyme preparations towards CMC did not change significantly during continuous operation over a periods of 60 days. Finally, xylan was hydrolyzed with the immobilized enzymes, and the sugars formed were investigated.     

Properties of enzymes immobilized by the diazotized m-diaminobenzene method.

Some properties of a number of enzymes immobilized by the diazotized m-diaminobenzene (dDAB) method are described. The pH-activity profiles of beta-D-glucosidase, glucoamylase, peroxidase, uricase, and D-glucose oxidase were virtually unchanged on immobilization while those of catalase and dextranase were significantly altered. beta-D-Glucosidase, glucoamylase, and glucose oxidase were found to be more susceptible to denaturation on lyophilization when immobilized than in the native state; however, sorbitol had a marked protective effect in every case examined. Sorbitol was also found to exert a stabilizing effect when lyophilized immobilized preparations were stored. Immobilization marginally improved the stabilities of a number of enzymes to heating at 60 degrees at pH 8.0. The usefulness for continuous reaction of a column of glucoamylase attached to celite was established. The reuse of the solid supports was demonstrated.     

Immobilized pectolytic enzymes on acrylic supports

The paper deals with the pectolytic enzymes immobilization on different acrylic supports, and the application of immobilized preparations in the apple juice pectinization process. The correlation between the protein content (C_p) and specific catalytic activities of immobilized enyzme preparations suggest a specific immobilization process only in the case of PONILEX ASH type acrylic supports. The active immobilization degree on PONILEX ASH type supports of Ultrazym 100 G and technical pectinase extract ranged from 99.80 to 296.40% for the Pectinesterase (PE) activity, and from 101.85 to 252.94% for the chain splitting (CS) activity, proving that the ionic immobilization process is a selective one. The simulated operational stability of the immobilized pectolytic enzymes tested by the PE and CS activity values proves the preservation of enzyme catalytic activity.     

Preparation and properties of immobilized papain and lipase.

Papain and lipase were immobilized on derivatized Sepharose 4-B. The activated agarose had a binding capacity of 1.2 micronmol amino groups/ml packed agarose or 17 mg proteins/g dry agarose. The immobilized enzyme preparations were tested for the effects of pH of assay, temperature of assay, and substrate concentrations. The effect of 6M urea on the activity of papain was also determined. Soluble forms of the enzymes were used for comparison. Immobilization of the enzymes resulted in slightly different pH and temperature optima for activities. For immobilized papain Km(app) was similar to the one observed with soluble papain. Immobilization of lipase, however, cause a decrease in Km values. The immobilized enzyme preparations were stable when stored at 4 degrees C and pH 7.5 for periods up to eight months. The soluble enzymes lost their activity within 96 hr under similar storage conditions. Immobilized papain did not lose any activity after treatment with 6M urea for 270 min, whereas soluble papain lost 81% of its activity after the urea treatment, indicating that the immobilization of papain imparted structural and conformational stability to this enzyme.     

Evaluation of the performance of immobilized penicillin G acylase using active-site titration

Penicillin G acylase from Escherichia coli was immobilized on Eupergit C with different enzyme loading. The activity of the immobilized preparations was assayed in the hydrolysis of penicillin G and was found to be much lower than would be expected on the basis of the residual enzyme activity in the immobilization supernatant. Active-site titration demonstrated that the immobilized enzyme molecules on average had turnover rates much lower than that of the dissolved enzyme. This was attributed to diffusion limitations of substrate and product inhibition. Indeed, when the immobilized preparations were crushed, the activity increased from 587 U g-1 to up to 974 U g-1. The immobilized preparations exhibited up to 15% lower turnover rates than the dissolved enzyme in cephalexin synthesis from 7-ADCA and D-(-)-phenylglycine amide. The synthesis over hydrolysis ratios of the immobilized preparations were also much lower than that of the dissolved enzyme. This was partly due to diffusion limitations but also to an intrinsic property of the immobilized enzyme because the synthesis over hydrolysis ratio of the crushed preparations was much lower than that of the dissolved enzyme.     

Enzymatic transglycosylation of natural and modified nucleosides by immobilized thermostable nucleoside phosphorylases from Geobacillus stearothermophilus

Natural and modified purine nucleosides have been synthesized using the recombinant thermostable enzymes purine nucleoside phosphorylase II (E. C. 2.4.2.1) and pyrimidine nucleoside phosphorylase (E. C. 2.4.2.2) from Geobacillus stearothermophilus B-2194. The enzymes were produced in recombinant E. coli strains and covalently immobilized on aminopropylsilochrom AP-CPG-170 after heating the cell lysates and the removal of coagulated thermolabile proteins. The resulting preparations of thermostable nucleoside phosphorylases retained a high activity after 20 reuses in nucleoside transglycosylation reactions at 70–75°C with a yield of the target products as high as 96%. Owing to the high catalytic activity, thermal stability, the ease of application, and the possibility of repeated use, the immobilized preparations of thermostable nucleoside phosphorylases are suitable for the production of pharmacologically important natural and modified nucleosides.     

Enzyme immobilization via monoclonal antibodies I. Preparation of a highly active immobilized carboxypeptidase A

A novel method for the preparation of highly active immobilized enzymes is described. It is based on the binding of enzymes to suitable carriers via monoclonal antibodies, which bind to the enzyme with high affinity without affecting its catalytic activity. The applicability of the method forwarded has been illustrated by the preparation of two samples of highly active immobilized carboxypeptidase A (CPA) preparations as follows: A mouse monoclonal antibody (mAb 100)to CPA that binds to the enzyme with a high-affinity constant without affecting its catalytic activity was prepared, purified, and characterized. Covalent binding of this monoclonal antibody to Eupergit C (EC) or noncovalent binding to Sepharose-protein A (SPA)yielded the conjugated carriers EC-mAb and SPA.mAb, respectively, which reacted specifically with CPA to give the immobilized enzyme preparations EC-mAb.CPA and SPA.mAb.CPA displaying full catalytic activity and improved stability. At pH 7.5 and a temperature range of 4-37 degrees C an apparent binding constant of approximately 10(8)M(-1) characterizing the interaction of CPA with EC-mAb and SPA.mAb, was obtained. To compare the properties of EC-mAb.CPA and SPA.mAb.CPA with those of immobilized CPA preparations obtained by some representative techniques of covalent binding of the enzyme with a corresponding carrier, the following immobilized CPA preparations were obtained and their properties investigated: EC-CPA (I), a preparation obtained by direct binding of EC with CPA; EC-NH-GA-CPA (II), a derivative obtained by covalent binding of CPA to aminated EC via glutaraldehyde; EC-NH-Su-CPA (III), a CPA derivative obtained by binding the enzyme to aminated EC via a succinyl residue; and EC-HMD-GA-CPA (IV), obtained by binding the enzyme via glutaraldehyde to a hexamethylene diamine derivative of EC. Full enzymic activity for all of the bound enzyme, such as that recorded for the immobilized CPA preparations EC-mAb.CPA and SPA.mAb.CPA, was not detected in any of the insoluble covalently bound enzyme preparations.     

Production of immobilized SalI and PvuII restrictase preparations

Conditions for the immobilization of specific endonucleases Sal I and Pvu II on BrCN-activated Sepharose 4B have been selected. Some physico-chemical properties of the preparations of immobilized restrictases Sal I and Pvu II have been characterized. The specific and general activity values of the preparations thus obtained have been established. The immobilized enzymes have been used for the multiple restriction of the DNA of phage lambda and the DNA of Neisseria meningitidis.     

Immobilized Human Plasmins: Preparation and Enzymatic Properties

Plasminogen was immobilized on agarose using either a commercially available substituted gel, or the cyanogen bromide (CNBr) activation procedure as a means of coupling the protein to agarose. Coupling the zymogen to the gel followed by its activation with urokinase yielded an immobilized plasmin. The immobilized enzymes have esterase, amidase and protease activity towards lysine and arginine esters, lysine anilide and casein, respectively. They activate plasminogen by a linear non-autocatalytic process. Both enzyme preparations are stable for extended periods of time in the absence of any stabilizing agents, and are not denatured by high salt concentrations or detergents.     

Studies on the stability of immobilized xanthine oxidase and urate oxidase.

The stability of immobilized preparations of xanthine oxidase and urate oxidase was studied, and optimized, because of the potential joint use of both enzymes in clinical analysis. Xanthine oxidase was immobilized on cellulose, Sepharose, hornblende, Enzacryl-TIO, and porous glass. Thehalf-lives of these preparations at 30 degree C ranged from 40 min to 5.0 hr. In this respect immobilized enzyme resembled soluble enzyme in dilute solution (0.11 mg/ml), when the half-live was about 3.5 hr. More concentrated enzyme solution (1 mg/ml) had a half-life of 64 hr, and was, therefore, considerably more stable than the untreated immobilized xanthine oxidase preparations. Inclusion of albumen in storage and assay buffer increased the half-life of bound xanthine oxidase. So also did treatment with glutaraldehyde: in the case of xanthine oxidase bound to Enzarcyl-TIO such treatment increased the half-life at 30 degree C from 3 hr to about 100 hr. Immobilized xanthine dehydrogenase was more stable than immobilized xanthine oxidase: the dehydrogenase lost no activity during continuous assay for 5 hr at 30 degree C. The stability of immobilized urate oxidase depended on the quantity of enzyme used and on the time of stirring during immobilization: thus a preparation was made (by stirring urate oxidase (48 mg/g support) with Enzacryl-TIO for 24 hr) which lost no activity during 350 hr at 30 degree C.     

Positive effects of the multipoint covalent immobilization in the reactivation of partially inactivated derivatives of lipase from Thermomyces lanuginosus

Different immobilized preparations of lipase from Thermomyces lanuginosus (TLL) have been inactivated by exposure to high temperatures, guanidine or 95% of dioxane. The studied preparations were: non-stabilized cyanogen bromide (CNBr-TLL), aminated CNBr-TLL (CNBr-TLL-A), and two stabilized preparations of aminated TLL by immobilization on glyoxyl support, Gx(9/10)-TLL-A (TLL-A immobilized at pH 9 and later incubated at pH 10) or Gx(10)-TLL-A (directly immobilized at pH 10). The reactivation of the partially inactivated immobilized enzymes under mild conditions by incubation in aqueous buffer, allowed recovery of some of the original activity, which was improved when it was pre-incubated in guanidine. Amination produced a fairly negative effect on the reactivation of the enzyme, but the multipoint covalent attachment of this aminated enzyme reversed the effect (e.g., recovered activity increased from 20% for CNBr-TLL to 80% for Gx(9/10)-TLL-A). The negative effect of the amination was clearer when the inactivation was caused by exposure to high temperatures, although the multipoint attachment of aminated enzyme was able to improve the recovered activity. The determination of enzyme activity in the presence of hexadecyltrimethylammonium bromide slowed the inactivation rates of all preparations and improved the recovery of activity after incubation under mild conditions, suggesting that the opening mechanism of the lipase could be a critical step in the TLL inactivation/reactivation. The use of multipoint attached TLL preparations did not only improve enzyme stability, but it also increased activity recovery when the preparation was incubated under mild conditions.     

Tuning of Lecitase features via solid-phase chemical modification: Effect of the immobilization protocol

Lecitase Ultra (a quimeric fosfolipase commercialized by Novozymes) has been immobilized via two different strategies: mild covalent attachment on cyanogen bromide agarose beads and interfacial activation on octyl-agarose beads. Both immobilized preparations have been submitted to different individual or cascade chemical modifications (amination, glutaraldehyde or 2,4,6-trinitrobenzensulfonic acid (TNBS) modification) in order to check the effect of these modifications on the catalytic features of the immobilized enzymes (including stability and substrate specificity under different conditions). The first point to be remarked is that the immobilization strongly affects the enzyme catalytic features: octyl-Lecitase was more active versus p-nitrophenylbutyrate but less active versus methyl phenylacetate than the covalent preparations. Moreover, the effects of the chemical modifications strongly depend on the immobilization strategy used. For example, using one immobilization protocol a modification improves activity, while for the other immobiled enzyme is even negative. Most of the modifications presented a positive effect on some enzyme properties under certain conditions, although in certain cases that modification presented a negative effect under other conditions. For example, glutaraldehyde modification of immobilized or modified and aminated enzyme permitted to improve enzyme stability of both immobilized enzymes at pH 7 and 9 (around a 10-fold), but only the aminated enzyme improved the enzyme stability at pH 5 by glutaraldehyde treatment. This occurred even though some intermolecular crosslinking could be detected via SDS-PAGE. Amination improved the stability of octyl-Lecitase, while it reduced the stability of the covalent preparation. Modification with TNBS only improved enzyme stability of the covalent preparation at pH 9 (by a 10-fold factor).     

Immobilization of β-glucosidase on an inorganic carrier

The enzymatic hydrolysis of cellobiose, an important intermediate of the decomposition of cellulose containing materials, with immobilized β-glucosidase preparations from Geotrichium candidum, Trichoderma lignorum and Aspergillus foetidus was examined At first it was the aim to prepare from differently purified samples with different specific cellobiase activities high active preparations on the basis of the inorganic carrier Silochrom S-80. Characteristics e.g. thermal stability and temperature and pH optimum of immobilized preparations were compared with those of soluble preparations Kinetics of cellobiose hydrolysis by immobilized enzyme preparations were studied.     

Epoxy-amino groups: a new tool for improved immobilization of proteins by the epoxy method

The properties of a new commercially available amino-epoxy support (amino-epoxy-Sepabeads) for immobilizing enzymes have been compared to those of conventional epoxy supports. The new support has a layer of epoxy groups over a layer of ethylenediamine that is covalently bound to the support. Thus, this support has a great anionic exchanger power and a high number of epoxy groups. We have found a number of advantages to this new heterofunctional support. Immobilization proceeds at low ionic strength using amino epoxy Sepabeads while requiring high ionic strength using conventional monofunctional epoxy supports. Immobilization is much more rapid using amino-epoxy supports than employing conventional epoxy supports. The possibility of achieving immobilized preparations in which the enzyme orientation may be different to that obtained using the traditional hydrophobic supports (with likely effects in terms of activity or stability). Stability of the immobilized enzyme has been found to be much higher using the new support than in preparations using the conventional ones in many cases. Here we show some examples of these advantages using different enzymes (beta-galactosidases, lipase, glutaryl acylase, invertase, and glucoamylase).     

Immobilization of enzymes on Spheron: 2. β-Amylase — The development of a column reactor—separator

The titanium-chelation method has been used to immobilize β-amylase (1,4-α-d-glucan maltohydrolase, EC 3.2.1.2) on to Spheron. On various grades of Spheron, protein coupling yields of 56–76% were obtained with barley and sweet-potato β-amylases. The specific enzymic activities of the immobilized enzymes fell in the range 3.7–7.6% of those of the soluble enzymes. The immobilized enzymes were more stable than the soluble, especially in the presence of l-cysteine and serum albumin. The presence of cysteine and serum albumin brought about increases in activity in the preparations, presumably by regenerating essential thiol groups in the enzyme which had been oxidized during the operations. Maltose could be separated from amylopectin and other large polysaccharides by chromatography on Spheron P100, and a system was developed in which maltose, produced by hydrolysis of amylopectin applied in pulses to a column of immobilized β-amylase, was separated from starting material and by-products on a second column of Spheron P100.     

Affinity chromatography of pancreatic carboxypeptidases using a carboxypeptidase inhibitor from potatoes as ligand

A two-step purification scheme based on affinity chromatography has been developed for bovine and porcine carboxypeptidases A and B. Enzyme preparations of high purity are achieved from extracts of pancreatic acetone powder in less than 1 day by this procedure. The application of trypsin-treated extracts of pancreatic acetone powder to immobilized carboxypeptidase inhibitor from potatoes results in the specific retention of the target exopeptidases. After clution of the bound carboxypeptidases A and B at high pH, the resultant mixture of the two enzymes is resolved by chromatography on a column of ?-amino-n-caproyl-d-arginine-Sepharose 4B. Overall yields of 70–80% of the purified enzymes have been obtained with no cross-contamination of detectable tryptic or chymotryptic activities of the preparations.     

Improving the activity and stability of Yarrowia lipolytica lipase Lip2 by immobilization on polyethyleneimine-coated polyurethane foam

In this study, polyurethane foam (PUF) was used for immobilization of Yarrowia lipolytica lipase Lip2 via polyethyleneimine (PEI) coating and glutaraldehyde (GA) coupling. The activity of immobilized lipases was found to depend upon the size of the PEI polymers and the way of GA treatment, with best results obtained for covalent-bind enzyme on glutaraldehyde activated PEI-PUF (MW 70,000 Da), which was 1.7 time greater activity compared to the same enzyme immobilized without PEI and GA. Kinetic analysis shows the hydrolytic activity of both free and immobilized lipases on triolein substrate can be described by Michaelis–Menten model. The K_m for the immobilized and free lipases on PEI-coated PUF was 58.9 and 9.73 mM, respectively. The V_max values of free and immobilized enzymes on PEI-coated PUF were calculated as 102 and 48.6 U/mg enzyme, respectively. Thermal stability for the immobilization preparations was enhanced compared with that for free preparations. At 50 °C, the free enzyme lost most of its initial activity after a 30 min of heat treatment, while the immobilized enzymes showed significant resistance to thermal inactivation (retaining about 70% of its initial activity). Finally, the immobilized lipase was used for the production of lauryl laurate in hexane medium. Lipase immobilization on the PEI support exhibited a significantly improved operational stability in esterification system. After re-use in 30 successive batches, a high ester yield (88%) was maintained. These results indicate that PEI, a polymeric bed, could not only bridge support and immobilized enzymes but also create a favorable micro-environment for lipase. This study provides a simple, efficient protocol for the immobilization of Y. lipolytica lipase Lip2 using PUF as a cheap and effective material.     

Immobilization of proteolytic complexes on pectin-containing carriers

A number of sorbents were synthesized on the basis of pectin and then used for immobilization of proteolytic complexes--pancreatin and protosubtilin. The best properties were shown by the enzyme preparations based on pectin, formaldehyde and melamin (PFM). Thus immobilization of pancreatin on PFM through Fe(III) ions gave a preparation with the activity of 79 000 mumole/g X h with respect to methyl ester of L-tryptophane (the activity yield is 91%). The pH optimum for all immobilized preparations was shifted towards the alkaline region. The thermostable fraction of the immobilized preparations retains the activity at 60 degrees for a long time.     

Bioconversion potential of plant enzymes for the production of pharmaceuticals

Plant enzymes are able to catalyze regio- and stereospecific reactions. Freely suspended and immobilized plant cells as well as enzyme preparations can therefore be applied for the production of pharmaceuticals by bioconversion, as such or in combination with chemical syntheses. This review paper deals with bioconversions of added precursors from natural or synthetic origin by several biocatalytic systems.     

Immobilization of enzymes and microbial cells using carrageenan as matrix.

Conditions for the gelation k-carrageenan, which is a new polymer for immobilization of enzymes and microbial cells, were investigated in detail. k-Carrageenan was easily induced to gel by contact with metal ions, amines, amino acid derivatives, and water-miscible organic solvents. By using this property of k-carrageenan, the immobilization of enzymes and microbial cells was investigated. Several kinds of enzymes and microbial cells were easily immobilized with high enzyme activities. Immobilized preparations were easily tailor-made to various shape such as cube, bead, and membrane. The obtained immobilized preparations were stable, and columns packed with them were used for continuous enzyme reaction for a long period. Their operational stabilities were enhanced by hardening with glutaraldehyde and hexamethylenediamine.