Immobilization of Arthrobacter simplex in a thermally reversible hydrogel: effect of temperature cycling on steroid conversion

Arthrobacter simplex cells, which convert the steroid hydrocortisone to prednisolone, have been entrapped in a thermally reversible hydrogel. Such hydrogels exhibit a lower critical solution temperature (LCST) wherein the gel shrinks and deswells when it is warmed through its LCST, and then reversibly expands and reswells when it is cooled below the LCST. The immobilized cell-hydrogel system has been thermally cycled between two temperatures, each below the LCST. The upper temperature was selected to be just below the LCST, where the gel deswells but does not collapse, as it does at the LCST. The thermal cycling acts like a "hydraulic pump" which enhances mass transfer of the substrate (hydrocortisone) in and the product (prednisolone) out of the gel, thereby increasing steroid conversion dramatically relative to isothermal operation at either the upper or lower temperature. The increased conversion can also be due in part to reduced product inhibition. Mass transfer resistance and product inhibition are among the most serious problems in immobilized biocatalyst technology and thermal cycling of LCST hydrogels is both a novel and useful approach to minimizing these problems.     

Semicontinual synthesis of alkyl galactosides using β-galactosidase entrapped in polyvinylalcohol hydrogel

Fungal β-galactosidase from Aspergillus oryzae was immobilized into polyvinylalcohol (PVA) hydrogel by LentiKats® technology and used for the production of short-chain alkyl glycosides. Ethyl- and propyl-β-d-galactopyranosides were prepared from lactose (100?g/L) and varying initial amounts of alcohol (10–30% v/v) at 40?°C and pH 4.5. The entrapped β-galactosidase preserved 50% of the initial transgalactosylation activity after 25 repeated cycles in the production of ethyl β-d-galactopyranoside. When 5% (v/v) propanol was used as an acceptor, the enzyme activity (30–32?U/g immobilized enzyme) remained constant for 25 repeated batch runs. These findings suggest that entrapped β-galactosidase into LentiKats® has a great potential to be one effective, reusable and easy producible biocatalyst for the production of alkyl glycosides in a large scale.     

Activity and stability of urease entrapped in thermosensitive poly(N-isopropylacrylamide-co-poly(ethyleneglycol)-methacrylate) hydrogel

Urease was entrapped in thermally responsive poly(N-isopropylacrylamide-co-poly(ethyleneglycol)-methacrylate), p[NIPAM-p(PEG)-MA], copolymer hydrogels. The copolymer membrane shows temperature-responsive properties similar to conventional p(NIPAM) hydrogels, which reversibly swell below and de-swell above the lower critical solution temperature of p(NIPAM) hydrogel at around 32 °C. The retained activities of the entrapped urease (in p[NIPAM-p(PEG)-MA]-4 hydrogels) were between 83 and 53 % compared to that of the same quantity of free enzyme. Due to the thermo-responsive character of the hydrogel matrix, the maximum activity was achieved at around 25 °C with the immobilized urease. Optimum pH was the same for both free and entrapped enzyme. Operational, thermal and storage stabilities of the enzyme were found to increase with entrapment of urease in the thermoresponsive hydrogel matrixes. As for reusability, the immobilized urease retained 89 % of its activity after ten repeated uses.     

A screen-printed biosensor using pyruvate oxidase for rapid determination of phosphate in synthetic wastewater

A screen-printed phosphate biosensor based on immobilized pyruvate oxidase (PyOD, E.C. 1.2.3.3) has been developed for monitoring phosphate concentrations in a sequencing batch reactor (SBR) system. The enzyme was immobilized by a nafion matrix and covered a poly(carbamoyl) sulfonate (PCS) hydrogel on a screen-printed electrode. PyOD consumes phosphate in the presence of pyruvate and oxygen and generates hydrogen peroxide (H₂O₂), carbon dioxide and acetylphosphate. The electroactive H₂O₂, monitored at +420 mV vs Ag/AgCl, is generated in proportion to the concentration of phosphate. The sensor has a fast response time (2 s) and a short recovery period (2 min). The time required for one measurement using this phosphate biosensor was 4 min, which was faster than the time required using a commercial phosphate testing kit (10 min). The sensor has a linear range from 7.5 M to 625 M phosphate with a detection limit of 3.6 M. There was good agreement (R²=0.9848) between the commercial phosphate testing kit and the phosphate sensor in measurements of synthetic wastewater in a SBR system. This sensor maintained a high working stability (>85%) after 12 h of operation and involved a simple operation procedure. It therefore serves as a useful tool for rapid and accurate phosphate measurements in the SBR system and probably for process control.     

Immobilization ofβ-fructofuranosidase fromAureobasidium on DEAE-cellulose

Summary -Fructofuranosidase, which produces fructo-oligosaccharides (1-kestose and nystose) from sucrose, was purified fromAureobasidium and immobilized on DEAE-cellulose at especially high efficiency (95%). The enzymatic profiles of the immobilized enzyme were almost identical to those of the native form except that the stability was slightly improved. The immobilized enzyme was stable during long-term continuous reaction for up to 360 h.     

The continuous hydrolysis of geniposide to genipin using immobilized β-glucosidase on calcium alginate gel

Summary The reaction velocity of immobilized -glucosidase was approximated by the first-order reaction kinetics. A plug flow reactor was used for continuous hydrolysis of geniposide with this immobilized enzyme. The activity of this immobilized enzyme was retained 100% for 600 h. The amount of genipin formed by using the immobilized enzyme was 17 fold that formed using the native enzyme without reuse. Using immobilized enzyme, purity and yield of genipin, which is a hydrolyzate of geniposide, was improved comparing with the native enzyme.     

Characteristics of yeast β-galactosidase immobilized on calcium alginate gels

Summary Saccharomyces anamensis having -galactosidase activity, has been immobilized in calcium alginate gel matrix that retained 78.6% enzyme activity to that of native cells. Optimum pH(7.0) was negligibly affected by immobilization. K_m values for immobilized and native cells were 119 mM and 102 mM respectively. Protective agents like dithioerythritol, bovine serum albumin, enhance the enzyme activity when added prior to immobilization. Immobilized cells can be stored in refrigeration(4°C) for 42 days without a significant loss of enzyme activity.     

Improvement of lipase activity by synergistic immobilization on polyurethane and its application for large-scale synthesizing vitamin A palmitate

Abstract

We have developed an improved and effective method to immobilize lipase on hydrophobic polyurethane foam (PUF) with different modifications. PUF was treated with hydrochloric acid to increase the active sites and then the active carboxyl groups and amino groups were exposed. Enzyme activity of lipase immobilized on PUF-HCL (8000?U/g) was 50% higher than that of lipase immobilized on PUF (5300?U/g). There is an increase in the activity of the immobilized lipase on AA/PEI-modified support (115,000?U/g), a 2.17-fold increase compared to lipase immobilized on the native support was observed. The activity of immobilized lipases was dependent on the PEI molecular weight, with best results from enzyme immobilized on PUF-HCL-AA/PEI (MW 70,000?Da, 12,800?U/g)), which was 2.41 times higher compared to that of the same enzyme immobilized on PUF. These results suggest that the activity of immobilized lipase is influenced by the support surface properties, and a moderate support surface micro-environment is crucial for improving enzyme activity. Finally, the immobilized lipase was used for the production of vitamin A palmitate. The immobilized lipase can be reused for up to 18 times with a conversion rate above 90% for 12?h in a 3?L bioreactor.

• Research highlights

• An efficient immobilization protocol on polyurethane foam was developed

• Polyethyleneimine and acetic acid were used to regulate the micro-environment concurrently

• The activity of lipase immobilized on PUF-HCL-AA/PEI was improved by 2.41 times

• Immobilized lipase exhibited excellent operational stability for vitamin A palmitate synthesis

     

Synthesis of electroconductive polyaniline using immobilized laccase

A new method for synthesis of the conductive complex between polyaniline (PANI) and poly(2-acrylamido-2-methyl-1-propanosulfonic acid) (PAMPS) was proposed; in this method, the immobilized laccase from the basidiomycete Trametes hirsuta is used as a biocatalyst for aniline oxidative polymerization. The conditions for laccase immobilization on CM cellulose by bifunctional Woodward’s reagent were optimized. The catalytic properties of immobilized and native laccases were compared. The immobilized laccase appeared an efficient catalyst for the oxidative radical polymerization of aniline on polysulfonic acid matrix at 4°C. It was demonstrated that the immobilized enzyme could be repeatedly used for enzymatic synthesis of this polymer. Several spectral characteristics of the PANI/PAMPS complexes synthesized at various pH values were studied. The conductance of PANI specimens produced using immobilized laccase as a catalyst was 13 mS/cm.     

Immobilization of alkaline protease from Conidiobolus macrosporus for reuse and improved thermal stability

Alkaline protease from Conidiobolus macrosporus was immobilized on polyamide using glutaraldehyde as a bifunctional agent. The immobilized enzyme was optimally active at a higher temperature of 50°C than the free enzyme (40°C ) and showed a ten-fold increased thermostability at 60°C compared to that of the free enzyme. The efficiency of immobilization was 58% under the optimal conditions of pH and temperature. There was a 14-fold decrease in the K _m of immobilized enzyme compared to the free enzyme. The immobilized enzyme was fully active even after twenty-two cycles of repeated use. It retained 80% activity at 50°C in presence of 8 M urea exhibiting its stability to the denaturant and was compatible with several commercial detergents.     

Continuous production of galacto-oligosaccharides from lactose using immobilized β-galactosidase from Bacillus circulans

Summary -Galactosidase-2 (-d-galactoside galactohydrolase, EC 3.2.1.23) from Bacillus circulans was purified using hydroxyapatite gel chromatography and immobilized onto Duolite ES-762 (phenolformaldehyde resin) and Merckogel (controlled pore silica gel) for continuous production of galacto-oligosaccharides using lactose as the substrate. The maximum amount of ologosaccharides produced by the immobilized enzyme was 35–40% of the total sugar during hydrolysis of 4.56% lactose. Partially purified -galactosidase from B. circulans was also immobilized onto various supports for the same purpose. The stability of the immobilized -galactosidase-2 or partially purified enzyme during a continuous reaction depended on their supports and specific activity. Of the supports tested, Merckogel was best for operational stability. With this support, the enzyme was quite stable with specific activity up to 15 units/g of wet gel; it was reversibly inactivated with more.     

Characterization of immobilized enzymes in polyurethane foams in a dynamic bed reactor

-d-Galactosidase (E 3.2.1.23) from Aspergillus oryzae was immobilized with polyurethane foam (PUF). Among several immobilization methods attempted in this work, the immobilized enzyme preparation by in-situ co-polymerization between enzyme and prepolymer HYPOL 3000 showed the highest activity. The intrinsic kinetics of PUF-immobilized enzyme was determined in a dynamic bed reactor, used to increase transport rates. The immobilization mechanism in PUF was studied by measurements of immobilized enzyme kinetics and by using scanning electron microscopy combined with immuno-gold labeling techniques. The results showed that immobilization was predominantly by covalent bonding between primary amino groups of -d-galactosidase and isocyanate groups of the prepolymers. Entrapment in the PUF micropores assisted the immobilization of enzymes, and adsorption on the surface of macropores was not important for immobilization. The bicinchoninic acid method was applied for the determination of PUF loading capacity and specific enzyme activity and used to determine enzyme deactivation during immobilization.     

Bacterial cellulose-chitosan composite hydrogel beads for enzyme immobilization

In this work, we report the preparation of bacterial cellulose (BC)-chitosan composite hydrogel beads by co-dissolution of BC and chitosan in 1-ethyl-3-methylimidazolium acetate and subsequent reconstitution with distilled water. The BC-chitosan hydrogel beads were used as enzyme supports for immobilizing Candida rugosa lipase by physical adsorption and covalent cross-linking. BC-chitosan hydrogel beads immobilized lipase more efficiently than microcrystalline cellulose (MCC)-chitosan hydrogel beads. The amount of protein adsorbed onto BCchitosan beads was 3.9 times higher than that adsorbed onto MCC-chitosan beads, and the catalytic activity of lipase was 1.9 times higher on the BC-chitosan beads. The lipase showed the highest thermal and operational stability when covalently cross-linked on BC-chitosan hydrogel beads. The half-life time of the lipase cross-linked on BC-chitosan bead at 60°C was 22.7 times higher than that of free lipase. Owing to their inherent biocompatibility and biodegradability, the BC-chitosan composite hydrogel beads described here could be used to immobilize proteins for various biomedical, environmental, and biocatalytic applications.     

Immobilization of glucoamylase onto polyaniline-grafted magnetic hydrogel via adsorption and adsorption/cross-linking

Glucoamylase (GA) was immobilized onto polyaniline (PANI)-grafted magnetic poly(2-hydroxyethylmethacrylate-co-glycidylmethacrylate) hydrogel (m-p(HEMA-GMA)-PANI) with two different methods (i.e., adsorption and adsorption/cross-linking). The immobilized enzyme preparations were used for the hydrolysis of “starch” dextrin. The amount of enzyme loading on the ferrogel was affected by the medium pH and the initial concentration of enzyme. The maximum loading capacity of the enzyme on the ferrogel was found to be 36.7 mg/g from 2.0 mg/mL enzyme solution at pH 4.0. The adsorbed GA demonstrated higher activity (59%) compared to adsorbed/cross-linked GA (43%). Finally, the immobilized GA preparations exhibited greater stability against heat at 55 °C and pH 4.5 compared to free enzyme (50 °C and pH 5.5), suggesting that the ferrogel was suitable support for immobilization of glucoamylase.     

Immobilization ofβ-fructofuranosidase fromAureobasidium sp. ATCC 20524 on porous silica

Summary -Fructofuranosidase P-1 fromAureobasidium sp. ATCC 20524, which produces a fructo-oligosaccharide (1-kestose) from sucrose, was immobilized covalently onto alkylamine porous silica with glutaraldehyde at high efficiency (44.4%). Optimum pore diameter of porous silica for immobilization of the enzyme was 91.7 nm. The enzymatic profiles of immobilized enzyme were almost identical to the native one except its stabilities to temperature and metal ions were improved. 1-Kestose was produced continuously and selectively from 40% (w/v) sucrose at fast flow rates by a column packed with the immobilized enzyme for up to 26 days, and the effluent concentration of 1-kestose remained in the range 113–135 mg ml^–1.     

Mechanism for reversible inactivation of immobilized β-galactosidase from Bacillus circulans during continuous production of galacto-oligosaccharides

Summary The specific activity-dependent stability of the immobilized -galactosidase-2 (-d-galactoside galactohydrolase, EC 3.2.1.23) from Bacillus circulans during the continuous production of galactooligosaccharides from lactose was studied. This was done by measuring the elution pattern of saccharides from the various immobilized Merckogel (controlled pore silica gel) columns and the amount of saccharides remaining in the gel. It was suggested that oligosaccharides produced were trapped inside the three dimensional enzyme aggregate with the immobilized enzyme having a specific activity of 240 units/g of wet gel, causing gradual inactivation, while the immobilized enzyme with 15 units/g of wet gel was stable since the oligosaccharides were not accumulated.Free -galactosidase-2 was stable during continuous reaction in a membrane reactor.     

Immobilization of <Emphasis Type="Bold">β</Emphasis>-fructofuranosidase from <Emphasis Type="Italic">Aspergillus japonicus</Emphasis> on chitosan using tris(hydroxymethyl)phosphine or glutaraldehyde as a coupling agent

A partially purified -fructofuranosidase from Aspergillus japonicus was covalently immobilized on to chitosan beads using either glutaraldehyde or tris(hydroxymethyl)phosphine (THP) as a coupling agent. Compared with the glutaraldehyde-immobilized and the free enzyme, the THP-immobilized enzyme had the highest thermal stability with 78% activity retained after 12 days at 37 ° C. The THP-immobilized enzyme also had higher reusability than that immobilized by glutaraldehyde, 75% activity was retained after 11 batches (or 11 days) at 37° C for the THP immobilized enzyme system. Less yield (48%) of fructooligosaccharides (FOS) were produced by the THP-immobilized enzyme compared with the free enzyme system (58%) from 50 (w/v) sucrose at 50 ° C.     

Immobilization of β-galactosidases from Thermus aquaticus YT-1 for oligosaccharides synthesis

Summary -galactosidases of Thermus aquaticus YT-1, exhibiting a galactosyl transferase activity, were immobilized using different techniques. Entrapment in agarose or gellan gum beads was unsuitable for enzyme immobilization due to enzyme leakage. A technique that efficiently immobilized the enzymes was developed using glutaraldehyde co-crosslinking of -galactosidases with bovine serum albumin, followed by entrapment in agarose beads.     

Immobilization and characterization of a thermostable β-galactosidase from a thermophilic anaerobe on a porous ceramic support

A thermostable -galactosidase (EC 3.2.1.23) from a thermophilic anaerobe, strain NA10, was purified from the crude extract of the Escherichia coli transformant harboring the lacN gene. The purified enzyme was physically and covalently immobilized to a porous ceramic support, SM-10. Among the supports tested, the highest residual activity after 3 h incubation at 70° C was obtained when the enzyme was covalently immobilized to silanized SM-10 with 3-[2-(2-amino-ethylaminoethylamino)propyl]trimethoxysilane. The amount of the enzyme immobilized was about 60 mg/g of this support. The enzymatic properties were almost the same as those of the free enzyme. The half-life of this immobilized enzyme was estimated to be approximately 450 h at the pasteurization temperature (65° C).On leave from Aichi Institute of Technology, Yakusa-cho, Toyota 470-03, Japan Correspondence to: T. Saito     

Glucoamylase and α-amylase production by immobilized Aspergillus niger

Summary Aspergillus niger mycelia or spores were immobilized in calcium alginate gel beads and employed for production of glucoamylase and -amylase by repeated batch process. The immobilized mycelium produced lower enzyme activities than immobilized spores germinated in a growth medium and subsequently cultured in an enzyme production medium. In repeated batch experiments, free cells could be used for only 4 4-day batches, whereas with immobilized spores at least 11 4-day batches with a gradual increase in enzyme activities in each successive batch were possible. The activity ratio of glucoamylase and -amylase produced was altered by immobilization.