Preparation and properties of proteases immobilized on anion exchange resin with glutaraldehyde

High activity alkaline protease was obtained when the enzyme was immobilized on Dowex MWA-1 (mesh 20–50) with 10% glutaraldehyde in chilled phosphate buffer (M/15, pH 6.5). Activity yields of the protease and rennet were 27 and 29, respectively. The highest activities appeared at 60°C, pH 10 for alkaline protease and 50°C, pH 4.0 for rennet. The properties of both proteases were not essentially changed by the immobilization except that the K_m values of both enzymes were increased about tenfold as a result of immobilization. Both proteases in the immobilized state were more stable than those in the free state at 60°C. Other peptide hydrolases, β-galactosidase, invertase, and glucoamylase, were successfully immobilized with high activities, but lipase, hexokinase, glucose-6-phosphate dehydrogenase, and xanthine oxidase became inactive.     

Protease production by immobilized mycelia of Streptomyces fradiae

Streptomyces fradiaewas immobilized in polyacrylamide gel prepared from 5% total acrylamide (90% acrylamide and 10%N,N′-methylenebisacrylamide). Production of protease by the immobilized mycelia was attempted in a batch system. A dilute medium containing 0.5% starch, 0.5% meat extract, and 0.05% yeast extract was employed. The reusability of the immobilized and washed mycelia was examined. The activity of protease production by washed mycelia was rapidly decreased with increasing use cycles. The activity of the immobilized mycelia increased gradually, and reached a maximum after ten use cycles. Then, the activity gradually decreased with increasing reaction cycles. This might be caused by destruction of the gels. On the other hand, the sterilization of the surface of the immobilized mycelia was effective for elongation of the lifetime. As a result, the half-life of protease production by the sterilized immobilized mycelia was about 30 days. The rate of protease production by immobilized mycelia was 12,000 U/ml/hr. This value was four times higher than that by submerged culture.     

α-Amylase production by immobilized whole cells of Bacillus subtilis

Summary Whole cells of Bacillus subtilis were immobilized in polyacrylamide gel prepared from 5% total acrylamide (85% acrylamide and 15% N,N-methylenebisacrylamide). Production of -amylase by the immobilized whole cells was attempted in a batch system. -Amylase produced by the immobilized whole cells was about three times larger than that produced by washed cells at optimum conditions. The reusability of the immobilized whole cells and washed cells was examined. The activity of -amylase production by washed cells decreased with increasing use cycles. On the other hand, the activity of the immobilized cells increased gradually, and it reched a steady state after seven cycles. -Amylase was produced from a simple reaction medium containing 1% meat extract and 0.05% yeast extract by the immobilized whole cells. The rate of -amylase production by the immobilized whole cells was the same as in submerged cultivation using starch bouillon medium. Growth of B. subtilis in polyacrylamide gel was observed by electron microscopy.     

Thermostable α-amylase production by immobilized Bacillus licheniformis cells in agar gel and on acrylonitrile/acrylamide membranes

Immobilized cells of Bacillus licheniformis 44MB82-G were used for the production of thermostable -amylase. The immobilization was carried out by entrapment in agar gel or by binding to formaldehyde-activated acrylonitrile/acrylamide membranes. The -amylase production after 144 h of cultivation of membrane immobilized cells was 40% higher in comparison with the free cells. The respective value for the agar-entrapped cells was 22%. Similar trends were observed in the repeated batch fermentations performed with the immobilized cells. The scanning electron micrographs (SEM) of the immobilized cells gave additional information about their binding to the respective carriers.     

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.     

Production of thermophilic α-amylase using immobilized transformed Escherichia coli by addition of glycine

Efficient production of thermophilic α-amylase from Bacillus stearothermophilus was investigated using recombinant Escherichia coli HB101/pH1301 immobilized with κ-carrageenan by the addition of glycine. The effects of glycine, the concentrations of κ-carrageenan and KCI on the production of the enzyme as well as the stability of plasmid pHI301 were studied. In the absence of glycine, the enzyme was localized in the periplasmic space of the recombinant E. coli cells and a small amount of the enzyme was liberated in the culture broth. Although the addition of glycine was very effective for release of α-amylase from the periplasm of E. coli entrapped in gel beads, a majority of the enzyme accumulated in the gel matrix. (In this paper, production of the enzyme from recombinant cells to an ambient is expressed by the term “release”, while diffusion-out from gel beads is referred to by the term “liberate”.) Concentrations of KCI and immobilizing support significantly affected on the liberation of α-amylase to the culture broth. Mutants which produced smaller amounts of the enzyme emerged during a successive culture of recombinant E. coli, even under selective pressure, and they predominated in the later period of the passages. The population of plasmid-lost segregants increased with cultivation time. The stability of pHI301 for the free cells was increased by the addition of 2% KCI, which is a hardening agent for carrageenan. Although the viability of cells and α-amylase activity in the beads decreased with cultivation time during the successive culture of the immobilized recombinant E. coli, the plasmid stability was increased successfully by immobilization. Efficient long-term production of α-amylase was attained by an iterative re-activation-liberation procedure using the immobilized recombinant cells. Although the viable cell number, plasmid stability and enzyme activity liberated in the glycine solution decreased at an early period in the cultivation cycles, the process attained steady state regardless of the addition of an antibiotic.     

Functional polymeric supports for immobilization of cholesterol oxidase

Here, we have reported the useful functional polymeric supports for possible application of enzyme immobilization. Functional polymers were prepared by free radical polymerization from different monomers (i.e., methylmetacrylate, glycidylmethacrylate, acrylamide, etc.) and N,N-methylenebis(acrylamide) (MBAAm) crosslinker. Cholesterol oxidase (ChOx) [EC.1.1.3.6] was then covalently immobilized onto these functional supports via epichlorohydrin (ECH) and carbodiimide (EDAC) as the activating agents. It was observed that, after 60th use in 5 days, the retained activities for immobilized enzymes onto poly(methyl methacrylate-co-glycidyl methacrylate) [P(MMA-co-GMA)] and poly(acrylamide-co-acrylic acid)/polyethyleneimine [P(AAm-co-AA)/PEI] supports were found as 56% and 83%, respectively.     

Amylase from Lactobacillus cellobiosus D-39 isolated from vegetable wastes: characteristics of immobilized enzyme and whole cell

Cells and partially purified α-amylase (EC 3.2.1.1) of the producer strain, Lactobacillus cellobiosus D-39 were immobilized on acrylamide gel. The enzyme showed marked improvement in operational stability. Both immobilized cells and enzyme were stable for a long period and no appreciable loss activity was detected on keeping at 4°C for 4 months. The amylase activity of immobilized cells and enzyme attained maximum at pH 6.0 and 7.6 respectively and at temperature 60°C for both cases. The effects of various solvents, detergent and metal ions were tested; Triton X-100 gave maximum stimulation of the enzyme activity of immobilized cells whereas metal ions exhibited no such enhancement for either of immobilized cells or enzyme.     

Immobilization of d-glucose oxidase onto a hydrogen peroxide permselective membrane and application for an enzyme electrode

A hydrogen peroxide permselective membrane with asymmetric structure was prepared and d-glucose oxidase (EC 1.1.3.4) was immobilized onto the porous layer. The activity of the immobilized d-glucose oxidase membrane was 0.34 units cm^?2 and the activity yield was 6.8% of that of the native enzyme. Optimum pH, optimum temperature, pH stability and temperature stability were found to be pH 5.0, 30–40°C, pH 4.0–7.0 and below 55°C, respectively. The apparent Michaelis constant of the immobilized d-glucose oxidase membrane was 1.6 × 10^?3 mol l^?1 and that of free enzyme was 4.8 × 10^?2 mol l^?1. An enzyme electrode was constructed by combination of a hydrogen peroxide electrode with the immobilized d-glucose oxidase membrane. The enzyme electrode responded linearly to d-glucose over the concentration 0–1000 mg dl^?1 within 10 s. When the enzyme electrode was applied to the determination of d-glucose in human serum, within day precision (CV) was 1.29% for d-glucose concentration with a mean value of 106.8 mg dl^?1. The correlation coefficient between the enzyme electrode method and the conventional colorimetric method using a free enzyme was 0.984. The immobilized d-glucose oxidase membrane was sufficiently stable to perform 1000 assays (2 to 4 weeks operation) for the determination of d-glucose in human whole blood. The dried membrane retained 77% of its initial activity after storage at 4°C for 16 months.     

Covalent binding of enzymes to synthetic membranes containing acrylamide units, using formaldehyde

Synthetic membranes containing 10% acrylamide units were subjected to activation with formaldehyde at pH 7.5 and 45 degrees C. Trypsin, invertase, and urease were bound to this activated membrane and the kinetic properties of immobilized enzymes were studied. The permeability of the membrane for distilled water manifests certain differences depending on the enzyme bound. The membranes with immobilized enzymes stored at 4 degrees C in a moist state showed no change in their activity for 6 months. The membrane with immobilized invertase has preserved its activity even after 20 operations with 2% sucrose solution at 25 degrees C. The proposed method of binding enzymes to synthetic membranes containing acrylamide groups, through the introduction of N-hydroxymethyl groups, possesses several advantages with respect to the activation of the membrane in a one-step reaction with cheap and accessible reagent, high operative stability of the immobilized enzymes, no danger of bacterial rotting, and long shelf life of the membrane.     

Optimization and enhanced production of α-amylase and protease by a newly isolated Bacillus licheniformis ZB-05 under solid-state fermentation

Eight different agro-residues were tested for α-amylase and protease production by using Bacillus licheniformis ZB-05. Among them, rice husk (RH) was proved as the best substrate for two enzymes (α-amylase 443 U/g and protease 469,000 U/g). Maximum enzyme production was observed to be 30 % initial moisture, with a growth period of 36 h in 20 and 30 % inoculum volumes for α-amylase and protease, respectively. The best enzyme recovery from solid mass was obtained when extracted with tap water. Among the tested various nitrogen sources, 1 % ammonium sulphate followed by 2 % Bacto liver, 2 % ammonium sulphate and 1 % Bacto casaminoacid served as the best inorganic and organic nitrogen sources for α-amylase and protease production, respectively. As additional carbon sources, 2 % soluble starch enhanced α-amylase production, while 1 % maltose enhanced protease production.     

Involvement of protein dynamics in enzyme stability. The case of glucose oxidase

Dynamics of glucose oxidase immobilized and in solution were compared through their tryptophan fluorescence spectra, decay times and quenching by acrylamide. Energy barrier for thermal inactivation and melting temperature of both soluble and immobilized enzyme were also measured. Data show that the fluctuation amplitude is at the origin of protein instability.     

Immobilization of Bacillus licheniformis cells, producers of thermostable α-amylase, on polymer membranes

Cells of Bacillus licheniformis 44MB82-G immobilized on different polymer membranes were used for production of thermostable α-amylase. The α-amylase yields of the membrane-immobilized cells were affected by the reactive chemical groups of the carriers and the spacer size. Formaldehyde-activated polysulphone membranes (PS-FA) were the most suitable for effective immobilization. The highest amylase yield (62% increase of the control) and operational stability (97% residual activity after 480 h repeated batch cultivation) were obtained with this system. This was confirmed by scanning electron micrographs. An additional increase of α-amylase production by PS-FA-membrane immobilized cells was achieved in a fluidized-bed reactor. Received 20 March 1997/ Accepted in revised form 08 January 1998     

Immobilization of glycoenzymes through carbohydrate side chains.

Glucoamylase, peroxidase, glucose oxidase, and carboxypeptidase Y were covalently bound to water-insoluble supports through their carbohydrate side chains. Two approaches were used. First, the carbohydrate portions of the enzymes were oxidized with periodate to generate aldehyde groups. Treatment with amines (ethylenediamine or glycyltyrosine) and borohydride provided groups through which the protein could be immobilized. Ethylenediamine was attached to glucoamylase, peroxidase, glucose oxidase, and carboxypeptidase Y to the extent of 24, 20, 30, and 15 mol/mol of enzyme, respectively. These derivatives were coupled to an aminocaproate adduct of CL-Sepharose via an N-hydroxysuccinimide ester or to CNBr-activated Sepharose. Coupling yields were in the range of 37–50%. Retained activities of the bound aminoalkyl-enzymes were 41% (glucoamylase), 79% (peroxidase), 71% (glucose oxidase), 83% (carboxypeptidase Y). A glycyltyrosine derivative of carboxypeptidase Y was bound to diazotized arylamine-glass. Coupling yield was 42% and retained esterase activity was 84%. In the second approach, the enzyme was adsorbed to immobilized concanavalin A and the complex was crosslinked. Adsorption of carboxypeptidase Y on immobilized concanavalin A followed by crosslinking with glutaraldehyde was also effective. The bound enzyme retained 96% of the native esterase activity and showed very good operational stability.     

Acrylamide synthesis using agar entrapped cells of <Emphasis Type="Italic">Rhodococcus rhodochrous</Emphasis> PA-34 in a partitioned fed batch reactor

The nitrile hydratase (Nhase) induced cells of Rhodococcus rhodochrous PA-34 catalyzed the conversion of acrylonitrile to acrylamide. The cells of R. rhodochrous PA-34 immobilized in 2% (w/v) agar (1.76 mg dcw/ml agar matrix) exhibited maximum Nhase activity (8.25 U/mg dcw) for conversion of acrylonitrile to acrylamide at 10°C in the reaction mixture containing 0.1 M potassium phosphate buffer (pH 7.5), 8% (w/v) acrylonitrile and immobilized cells equivalent to 1.12 mg dcw (dry cell weight) per ml. In a partitioned fed batch reaction at 10°C, using 1.12 g dcw immobilized cells in a final volume of 1 l, a total of 372 g of acrylonitrile was completely hydrated to acrylamide (498 g) in 24 h. From the above reaction mixture 87% acrylamide (432 g) was recovered through crystallization at 4°C. By recycling the immobilized biocatalyst (six times), a total of 2,115 g acrylamide was produced.     

The properties of immobilized whole cell ofHumicola spp. with rifamycin oxidase activity

Summary The whole cell ofHumicola spp. ATCC 20620 with rifamycin oxidase activity was immobilized by copolymerization with acrylamide. The whole cell was defatted by treatment with acetone to reduce the diffusional resistance through the cell membrane. The recovery of enzyme activity after the immobilization step was about 50%. The acetone-defatted cell showed the maximum activity at pH 7.5 for both free and the immobilized forms. No appreciable activity loss could be detected when stored at 4 °C and pH 7.8 for one month, while the half life at 40 °C and pH 8 was decreased to about 8 days. The apparent Km values of rifamycin oxidase for the free and immobilized acetonedefatted cells were 0.3mM and 0.6mM, respectively. The enzyme demonstrated substrate inhibition, but the degree of substrate inhibition was different between two forms of the enzyme preparation. A complete substrate inhibition was observed for the immobilized cell, whereas the enzyme activity was partially inhibited at high substrate concentration in the acetone-defatted cells.     

Stabilization ofd-amino-acid oxidase fromTrigonopsis variabilis by manganese dioxide

Stabilization of immobilized D-amino-acid oxidase was achieved as follows. Yeast Trigonopsis variabilis producing D-amino-acid oxidase was used to deaminate cephalosporin C to glutaryl-7-aminocephalosporanic acid. Permeabilized cells were co-immobilized with manganese dioxide by entrapment in (poly)acrylamide gel so that hydrogen peroxide, liberated in the reaction, could be partially deactivated and both the enzyme and the substrate could be stabilized. Activity of entrapped cells was determined by HPLC and enzyme flow microcalorimetry. The process was evaluated in terms of activity, immobilization yield, storage stability and oxo-product formation by immobilized preparations. The storage stability of immobilized biocatalysts with MnO2 was nearly doubled and production of 2-oxoadipyl-7-aminocephalosporanic acid was 2-3-fold higher than by entrapped cells without MnO2. Glutaryl-7-aminocephalosporanic acid can be easily obtained from the resulting oxo-product by a non-enzymic reaction via externally added hydrogen peroxide.     

Exquisite regioselectivity and increased transesterification activity of an immobilized Bacillus subtilis protease

Commercially available proteases and lipases were screened for their ability to acylate regioselectively sucrose with divinyladipate either in pyridine or dimethylformamide (DMF). The protease (EC 3.4.21.62) from Bacillus subtilis (Proleather FG-F) exhibited the highest conversion (100% in 24 h of reaction in DMF) yielding sucrose 2-O-vinyladipate as main product. The enzyme preference for a secondary hydroxyl group is a distinct feature of this biocatalyst compared to others described in the literature. Two sets of chemically distinct silica supports were used for Proleather immobilization presenting terminal amino (S(APTES)) or hydroxyl groups (S(TESPM)(-)(pHEMA)). The percentage of immobilized enzyme was smaller in S(APTES) (7-17%) than in S(TESPM)(-)(pHEMA) (52-56%), yet Proleather immobilized into S(APTES) supports presented higher total and specific hydrolytic activity. The highest total and specific activities were obtained with S(TESPM)(-)(pHEMA) and S(APTES), respectively. Silicas with large pore (bimodal distribution of pores, 130/1200 A, denoted as S(1000)) presented higher specific activities relative to those with smaller pore sizes. Furthermore, the synthetic specific activity of S(1000)S(APTES) immobilized protease was ca. 10-fold higher than that of the free enzyme. In addition to sucrose, the immobilized protease was used to acylate methyl alpha-D-glucopyranoside, trehalose, and maltose in nearly anhydrous DMF. Finally, immobilized Proleather was reasonably stable, retaining ca. 55% activity after six reaction cycles.     

Immobilization and characterization of D-amino acid oxidase.

Optimal conditions with respect to pH, concentration of glutaraldehyde and enzyme, and order of addition of enzyme and crosslinking reagent were established for the immobilization of hog kidney D-amino acid oxidase to an attapulgite support. Yields of 40 to 70% were generally attained although when low concentrations of enzyme were used yields were consistently greater than 100%. It is suggested that this is due to a dimer leads to monomer shift at low protein concentrations. The stability of soluble D-amino acid oxidase was dependent on the buffer in which it was stored (pyrophosphate-phosphate greater than borate greater than Tris). Stability of immobilized enzyme was less than soluble in pyrophosphate-phosphate buffer, but storage in the presence of FAD improved stability. In addition, treatment of stored, immobilized enzyme with FAD before assay restored some of its activity. The immobilized D-amino acid oxidase was less stable to heat (50 degrees C) than the soluble enzyme from pH 6 to 8 but was more stable above and below these values. Apparent Km values for D-alanine, D-valine, and D-tryptophan decreased for the immobilized enzyme compared to the soluble.