Stabilization of proteases by entrapment in a new composite hydrogel

A new one-step procedure for entrapping proteases into a polymeric composite calcium alginate-poly(N-vinyl caproladam) hydrogel was developed that provided 75–90% retention of the activity of entrapped enzymes compared to soluble ones. Properties of entrapped carboxypeptidase B, trypsin, and thrombin were investigated. The immobilized enzymes were active within a wide pH range. The temperature optima of entrapped trypsin and carboxypeptidase B were approx 25°C higher than that of the soluble enzymes, and the resistance to heating was also increased. The effects of various polar and nonpolar organic solvents on the entrapped proteases were investigated. The immobilized enzymes retained their activity within a wide concentration range (up to 90%) of organic solvents. Gel-entrapped trypsin and carboxypeptidase (CPB) were successfully used for obtaining human insulin from recombinant proinsulin. The developed stabilization method can be used to catalyze various reactions proceeding within wide pH and temperature ranges.     

Enantioselective hydrolysis of a Schiff's base of D,L-Phenylalanine ethyl ester in water-poor media via the reaction catalyzed with α-chymotrypsin immobilized on hydrophilic macroporous gel support

The application of immobilized α-chymotrypsin for the purpose of enantioselective hydrolysis of a Schiff's base of D,L-Phe-OEt (D,L-SBPH) in the mixed water-acetonitrile media with the different content of water is described. The immobilized biocatalyst was prepared by the chemical coupling of the enzyme to poly(vinyl alcohol) (PVA) cryogel—the macroporous hydrogel prepared by means of the freezing-thawing techniques. SBPH is water insoluble, and, therefore, acetonitrile (MeCN) with minor water additives was used as a solvent for the reaction of enantics elective hydrolysis of the racemic substrate. The process was conducted for 96–200 h, and L-Phe with the purity up to 98% e.e. precipitated in both the reaction medium and gel-carrier bulk. Theproduct wasrecovered by washing the organo-insoluble sediment with aqueous ammonia. D-Phe with the purity up to 85% e.e. was recovered from the organic solution of D-ester after its acidic hydrolysis. The PVA-cryogel-attached enzyme was effective in SBPH hydrolysis in MeCN/water mixtures. The immobilized biocatalyst was active for more than 1 mo of application and could be successfully used after another 4 mo storage at +10°C.     

Design of enzyme reactors as chromatographic columns for racemic resolution of amino acid esters

Summary Racemic resolution of aromatic and aliphatic amino acid esters into L-amino acid and D-amino acid ester via LC and HPLC is achieved by using enzyme reactors as chromatographic columns. For this purpose α-chymotrypsin and trypsin are immobilized on Eupergit C, Sepharose 4B and Lichrosorb-Diol.     

Controlled hydrolysis of cheese whey proteins using trypsin and α-chymotrypsin

This study examined the production of protein hydrolysates with controlled composition from cheese whey proteins. Cheese whey was characterized and several hydrolysis experiments were made using whey proteins and purified β-lactoglobulin, assubstrates, and trypsin and α-chymotrypsin, as catalysts, at two tem peratures and several enzyme concentrations. Maximum degrees of hydrolysis obtained experimentally were compared to the theoretical values and peptide compositions were calculated. For trypsin, 100% of yield was achieved; for α-chymotrypsin, hydrolysis seemed to be dependent on the oligopeptide size. The results showed that the two proteases could hydrolyze β-lactoglobulin. Trypsin and α-chymotrypsin were stable at 40°C, but a sharp decrease in the protease activity was observed at 55°C.     

Enzymatic hydrolysis of starch in water-immiscible organic solvent,two-phase systems

Enzyme-catalyzed hydrolyzations of starch by α-amylase have been studied in various two-phase systems, consisting of water and a water-immiscible organic solvent. The hydrolytic conversion of soluble starch to malto-oligosaccharides by α-amylase was greatly accelerated in 10% (v/v) water content of water-dodecane two-phase systems. However, a rapid inactivation of the enzyme has been observed in these systems. Addition of surfactant to these systems, such as polyoxyethylene (20) sorbitan monopalmitate (Tween 60) or bis(2-ethylhexyl) sodium sulfosuccinate (AOT), was effective for the enzyme stability. Effects of enzyme immobilization on the stability of α-amylase, using Ca-alginate and chitosan beads, also have been studied. The stability of immobilized enzyme was clearly enhanced in a 5–10% (v/v) water content two-phase system, whereas the free enzyme was inactivated within 41 h, remaining at a relative activity of 47–76% after 41 h of treatment. Furthermore, scanning electron micrographs (SEM) were taken to observe the effect of the two-phase system on the hydrolysis of starch. Potato starch granules have been extremely swelled and burst out in the stirred 10% (v/v) water content system, which did not contain enzymes.     

Lactose Hydrolysis by β-Galactosidase Covalently Immobilized to Thermally Stable Biopolymers

Lactose has been hydrolyzed using covalently immobilized β-galactosidase on thermally stable carrageenan coated with chitosan (hydrogel). The hydrogel’s mode of interaction was proven by Fourier transform infrared spectroscopy, differential scanning calorimetry (DSC), and Schiff’s base formation. The DSC thermogram proved the formation of a strong polyelectrolyte complex between carrageenan and chitosan followed by glutaraldehyde as they formed one single peak. The modification of carrageenan improved the gel’s thermal stability in solutions from 35 °C to 95 °C. The hydrogel has been proven to be efficient for β-galactosidase immobilization where 11 U/g wet gel was immobilized with 50% enzyme loading capacity. Activity and stability of free and immobilized β-galactosidase towards pH and temperature showed marked shifts in their optimum pH from 4.5–5 to 5–5.5 and temperature from 50 °C to 45–55 °C after immobilization, which reveals higher catalytic activity and reasonable stability at wider pHs and temperatures. The apparent K _m of the immobilized enzyme increased from 13.2 to 125 mM, whereas the V _max increased from 3.2 to 6.6 μmol/min compared to the free enzyme, respectively. The free and immobilized enzymes showed lactose conversion of 87% and 70% at 7 h, respectively. The operational stability showed 97% retention of the enzyme activity after 15 uses, which demonstrates that the covalently immobilized enzyme is unlikely to leach. The new carrier could be suitable for immobilization of other industrial enzymes.     

Capabilities of polymer-modified monodisperse colloidal silica particles as biomaterial carrier

 Polymer modification of monodispersed colloidal silica (0.5 μm) with poly(maleic anhydride-co-styrene) (P(MA-ST)) and poly (maleic anhydride-co-methyl methacrylate) (P(MA-MMA)) and application of the composite particles to biomaterial carriers were investigated. The reaction of bovine serum albumin(BSA)-immobilized P(MA-MMA)/SiO₂ with the anti-BSA antibody showed higher sensitivity in immunological agglutination test than BSA–P(MA-ST)/SiO₂, though immobilization efficiency of BSA on P(MA-MMA)/SiO₂ was lower than that on P(MA-ST)/SiO₂. Alkaline phosphatase and glucose oxidase immobilized on the composite particles exhibited extremely low activities, but α-chymotrypsin immobilized on P(MA-MMA)/SiO₂ and its derivative particles showed the relative activity of 12.5% and 16.1% to the native enzyme, respectively. Grafting of a hydrophilic polymer of poly(acrylic acid) to P(MA-ST)/SiO₂ let to an increase of the immobilized α-chymotrypsin activity to give the maximum relative activity of 55.5%. Received: 23 August 1996 Accepted: 16 October 1996     

Immobilization of β-Galactosidase onto Magnetic Beads

A study of the cross-linking of β-galactosidase on magnetic beads is reported here. The magnetic beads were prepared from artemisia seed gum, chitosan, and magnetic fluid in the presence of a cross-linking regent (i.e., glutaraldehyde). The reactive aldehyde groups of the magnetic beads allowed the reaction of the amino groups of the enzymes. The animated magnetic beads were used for the covalent immobilization of β-galactosidase. The effect of various preparation conditions on the activity of the immobilized β-galactosidase, such as immobilizing time, amount of enzyme, and the concentration of glutaraldehyde, were investigated. The influence of pH and temperature on the activity and the stability of the enzyme, both free and immobilized, have been studied. And o-nitrophenyl-β-d-galactopyranoside (ONPG) was chosen as a substrate. The β-galactosidase immobilized on the magnetic beads resulted in an increase in enzyme stability. Optimum operational temperature for immobilized enzyme was 10 °C higher than that of free enzyme and was significantly broader.     

Preparation of alginate coated chitosan hydrogel beads by thermosensitive internal gelation technique

Chitosan hydrogel beads were successfully prepared by the method of thermosensitive internal gelation technique. The prepared beads were spherical, smooth-surfaced and non-aggregated with a diameter of 1.7–2.1 mm. The diameters of beads can be controlled and have a correlation with the initial drop size, the concentration of CaCl₂, alginate and the time of solidification. The bead is comprised of three parts, which are chitosan/glycerophosphate (CS/GP) hydrogel core, chitosan-alginate (CS/SA) gel layer in the middle and calcium-alginate gelatin capsules in outer layer. Swelling studies indicate that the beads can be stable in simulated gastric fluid. But the beads shrink sharply when removed to simulated intestinal fluid. Drug release behavior showed that release of ornidazole in the beads is much slower than in the CS/GP hydrogel.     

Enantioselective Resolution of γ-Lactam by a Whole Cell of <Emphasis Type="Italic">Microbacterium hydrocarbonoxydans</Emphasis> (L29-9) Immobilized in Polymer of PVA–Alginate–Boric Acid

Using immobilized cells of a novel strain of Microbacterium hydrocarbonoxydans L29-9 in polymers of polyvinyl alcohol (PVA)–alginate–boric acid, enantioselective resolution of racemic γ-lactam to produce (−)γ-lactam was successfully carried out. A 6:1 ratio of PVA:sodium alginate not only prevented agglomeration of the matrix but also produced beads with high gel strength. The optimum biotransformation conditions were 1 g/L substrate, pH 7.0, reaction temperature of 30 °C, and reaction time of 3 h. After every two cycles, the immobilized cell beads were separated and immersed in 0.5 mM KCl solution at 4 °C for preservation. At optimum conditions, the enantiomeric excess and the yield of (−)γ-lactam were >99% and 34%, respectively. The beads showed a slight decrease in the enantiomeric excess when re-used up to 14 cycles (the enantioselectivity of the immobilized cells decreased slightly after 14 cycles of usage).     

Preparation and properties of enzymes immobilized on supports activated by metal ions

Summary 1. Preparations of trypsin, -chymotrypsin, and glucose oxidase immobilized on synthetic and polysaccharide supports charged with transition-metal ions contain 3–64 mg of protein per 1 g of support.2. The activity of immobilized enzymes amounts to 100–10,000 U/g. The activity yield is 2.2–90X%.3. The pH dependence of the enzymes is shifted in the alkaline direction by 0.26–1.19 units. The Michaelis constants and inhibitor constants have decreased by factors of 1.5–21.4. The mechanism of the fixation of enzymes is determined by the formation of coordination bonds and by inclusion in inorganic gels. The properties of the enzymes are due to the surface charge of the activated supports.Institute of Biochemistry, Academy of Sciences of the Lithuanian SSR, Vilnius. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 629–637, September–October, 1978.     

Immobilization of prostaglandin synthetase by hydrophobic adsorption

In this article, the immobilization of prostaglandin synthetase onn-alkyl or aryl amino-agar beads by hydrophobic adsorption is reported. The effects of different hydrophobic groups in the agar beads, pH of buffer, concentration of salts on the adsorption of prostaglandin synthetase, and the properties of immobilized prostaglandin synthetase were also studied. The results showed that 20–35 mg of microsome containing PG synthetase (protein content 8–15 mg) could be adsorbed on each gram ofn-dodecylamino-agar beads after suction drying the gel in the buffer of pH 5.5 (containing 0.5 mol/L KC1), 0.1 mol/L citric-phosphate at 4‡C. The remaining immobilized enzyme activity was over 80%. The optimum pH of immobilized PG synthetase is 8.0, similar to that of the native enzymes. The thermostability of immobilized PG synthetase in the buffer containing 0.5 mol/L KC1 was increased. Immobilized PG synthetase was used as a catalyst of synthesis of prostaglandin E₁. The preservation of activity after 10 working cycles was 86.2%.     

Continuous cultivation of dilute-acid hydrolysates to ethanol by immobilized Saccharomyces cerevisiae

The continuous cultivation of immobilized Saccharomyces cerevisiae CBS 8066 on dilute-acid hydrolysates of forest residuals was investigated. The yeast cells were immobilized in 2–4% Ca-alginate beads. The 2% beads were not stable. However, the 3 and 4% beads were stable for at least 3 wk when an extra resource of calcium ions was available in the medium. The continuous cultivation of a dilute-acid hydrolysate by the immobilized cells at dilution rates of 0.3, 0.5, and 0.6 h⁻¹ resulted in 86, 83, and 79% sugar consumption, respectively, and an ethanol yield between 0.45 and 0.48 g/g. The hydrolysate was fermentable at a dilution rate of 0.1 h⁻¹ in a free-cell system but washed out at a dilution rate of 0.2 h⁻¹. The continuous cultivation of a more inhibiting hydrolysate was not successful by either free- or immobilized-cell systems even at a low dilution rate of 0.07 h⁻¹. However, when the hydrolysate was overlimed, it was fermentable by the immobilized cells at a dilution rate of 0.2 h⁻¹.     

Adsorption of 4-nonylphenol ethoxylates onto insoluble chitosan beads bearing cyclodextrin moieties

In order to develop a treatment method for industrial wastewater, the adsorption of 4-nonylphenol ethoxylates (NPEs), non-ionic surfactants used in the industry, onto chitosan beads having cyclodextrin (CDC beads) was investigated. Three kinds of CDC beads containing different cyclodextrin (CD) moieties were prepared from poly-carboxymethylated α-, β- and γ-CDs. Among α-, β- and γ-CD cavities, β-CD was the most suitable for the adsorption of the phenol derivatives. The amount of adsorption was greater for the NPEs having shorter ethoxylates. Most of the NPE adsorbed on the β-CDC beads were successfully released by the treatment of the CDC beads with various aqueous alcohol solutions. After 20 cycles of the adsorption–desorption were completed, no significant decline in the adsorption amount was observed. Continuous adsorption tests were carried out using the CDC beads filled in a glass column. At the appropriate flow rate, the NPE can be adsorbed with a reasonable saturation amount.     

Reverse hydrolysis reaction in aqueous medium without any cosolvent

The synthesis of L-tyrosine fructosyl ester, from fructose and L-tyrosine methyl ester, was carried out by a transesterification reaction catalyzed by α-chymotrypsin in water without cosolvent. The effect of fructose concentration and temperature for the transesterification reaction were determined on both specific activities and product yield. The influence of the presence of fructose has been studied regarding α-chymotrypsin and L-tyrosine fructosyl ester stabilities. It appeared that an increase of temperature enhanced enzyme activity but slumped the product yield because of the very weak stability of tyrosine fructosyl ester.     

Lipase immobilized on poly(VP-co-HEMA) hydrogel for esterification reaction

Lipase from Candida rugosa was immobilized by entrapment on poly(N-vinyl-2-pyrrolidone-co-2-hydroxyethyl methacrylate)(poly[VP-co-HEMA]) hydrogel, and divinylbenzene was the crosslinking agent. The immobilized enzymes were used in the esterification reaction of oleic acid and butanol in hexane. The activities of the immobilized enzymes and the leaching ability of the enzyme from the support with respect to the different compositions of the hydrogels were investigated. The thermal, solvent, and storage stability of the immobilized lipases was also determined. Increasing the percentage of composition of VP from 0 to 90, which corresponds to the increase in the hydrophilicity of the hydrogels, increased the activity of the immobilized enzyme. Lipase immobilized on VP(%):HEMA(%) 90∶10 exhibited the highest activity. Lipase immobilized on VP(%):HEMA(%) 50∶50 showed the highest thermal, solvent, storage, and operational stability compared to lipase immobilized on other compositions of hydrogels as well as the native lipase.     

Surface functionalization via in situ interaction of plasma-generated free radicals with stable precursor-molecules on cellulose

The surface functionalization process was accomplished in a consecutive 3 step process including: (1) Argon- and oxygen-plasma enhanced generation of free radical sites on cellophane surfaces; (2) “In situ” gas phase derivatization in the absence of plasma using hydrazine, ethylene diamine, or propylene diamine; (3) Second “in situ”, gas phase derivatization in the absence of plasma using oxallyl chloride or “ex situ” derivatization in the presence of glutaraldehyde. The presence of free radical sites on the plasma exposed cellophane surfaces was demonstrated using “in situ” sulfur dioxide and nitric oxide labeling techniques. It was shown that the free radical sites readily react under “in situ” conditions with the stable chain-precursor components and generate the desired spacer-chain molecules. ESCA, ATR-FTIR analysis and dying techniques were used to monitor the cellophane surface changes. A factorial design was used for selecting the optimal plasma parameters. Functionalized cellophane substrates were used for immobilization of α-chymotrypsin in the presence of spacer-chain molecules. The activity of the immobilized α-chymotrypsin was found to be lower in comparison to the activity of the free enzyme and the presence of virgin cellophane in the free enzyme solution also reduced significantly the activity of the enzyme. It is suggested that the swollen state of the cellophane plays a significant role in the decrease of the immobilized enzyme activity.     

Immobilization of Naringinase in PVA–Alginate Matrix Using an Innovative Technique

A synthetic polymer, polyvinyl alcohol (PVA), a cheap and nontoxic synthetic polymer to organism, has been ascribed for biocatalyst immobilization. In this work PVA–alginate beads were developed with thermal, mechanical, and chemical stability to high temperatures (<80 °C). The combination of alginate and bead treatment with sodium sulfate not only prevented agglomeration but produced beads of high gel strength and conferred enzyme protection from inactivation by boric acid. Naringinase from Penicillium decumbens was immobilized in PVA (10%)–alginate beads with three different sizes (1–3 mm), at three different alginate concentrations (0.2–1.0%), and these features were investigated in terms of swelling ratio within the beads, enzyme activity, and immobilization yield during hydrolysis of naringin. The pH and temperature optimum were 4.0 and 70 °C for the PVA–alginate-immobilized naringinase. The highest naringinase activity yield in PVA (10%)–alginate (1%) beads of 2 mm was 80%, at pH 4.0 and 70 °C. The Michaelis constant (K _Mapp) and the maximum reaction velocity (V _maxapp) were evaluated for both free (K _Mapp = 0.233 mM; V _maxapp = 0.13 mM min⁻¹) and immobilized naringinase (K _Mapp = 0.349 mM; V _maxapp = 0.08 mM min⁻¹). The residual activity of the immobilized enzyme was followed in eight consecutive batch runs with a retention activity of 70%. After 6 weeks, upon storage in acetate buffer pH 4 at 4 °C, the immobilized biocatalyst retained 90% of the initial activity. These promising results are illustrative of the potential of this immobilization strategy for the system evaluated and suggest that its application may be effectively performed for the entrapment of other biocatalysts.     

Stereospecific mannosylations of myo -inasitol: Synthesis of manno- myo -inositol fragment of Mycobacterium tuberculosis

Methyl iodide activated stereospecific α-mannosylations utilising 2-pyridyl-1-thiomannopyranoside derivatives (2,3,4) as donors and suitably protected myo-inositol derivatives (1,25,27,29) as acceptors to prepare 2-0-α-D-mannopyranosyl-6-[O-α-D-mannopyranosyl-(1–6)-O-α-D-mannopyranosyl-(l-6)-O-α-D-mannopyranosyl]-D-myo-inositol derivative (31) is described. IICT Commun. No. 3355     

Relationship between the hydration degree of poly-N-isopropylacrylamide gel and activity of immobilized α-chymotrypsin

The influence of the pH, temperature, and dimethyl sulfoxide concentration on the hydration degree of the poly-N-isopropylacrylamide gel and the activity of -chymotrypsin immobilized into the polymer was studied. The behavior of more hydrophilic preparations based on polyacrylamide and copolymer of acrylamide and acrylic acid was studied for comparison. An increase in both the temperature and dimethyl sulfoxide content decreases the hydration of the poly-N-isopropylacrylamide, which correlates with a decrease in the activity of the immobilized enzyme. The use of substrates with different structures and an irreversible inhibitor proves that the change in the properties of -chymotrypsin immobilized into the poly-N-isopropylacrylamide gel is related to the change in the rate constants of enzymatic reactions. Comparison of all experimental data obtained suggested an opportunity of local interactions between the protein globule and polymeric chains with a change in the hydration degree of poly-N-isopropylacrylamide during its phase transition.