Preparation and characterization of trypsin immobilized on silica gel supported macroporous chitosan bead

Zinc oxide nanoparticles-impregnated chitosan surfaces for covalent immobilization of trypsin: Stability & kinetic studies

Trypsin (Try, EC. 3.4.21.4) was effectively immobilized on the surface of glutaraldehyde(GA)-activated ZnO/Chitosan nanocomposite through covalent attachment via Schiff-base linkages. Size, structure, surface morphology, & percentage elemental composition of the prepared ZnO nanoparticles and chitosan-coated ZnO nanocomposite were studied by UV-Visible spectroscopy, Fourier-transform infrared spectroscopy (FTIR), X-Ray diffraction analysis (XRD), transmission electron microscopy (TEM), Scanning electron microscopy (SEM), and Energy-Dispersive X-Ray Microanalysis (EDAX) techniques. Optimal immobilization conditions (incubation time (16 h), enzyme concentration (1.8 mg/ml), and pH (7.8)) were investigated to obtain the maximum expressed activity of the immobilized trypsin. Immobilized & solubilized trypsin exhibited the optimum catalytic activity at pH 8.5, 60 °C, and pH 7.8, 45 °C respectively. Kinetic parameters (K_m, V_max) of immobilized (27.12 μM, 8.82 μM/min) & free trypsin (25.76 μM, 4.16 μM/min) were determined, indicating that efficiency of trypsin improves after immobilization. Immobilized trypsin preserved 67% of initial activity at 50 °C during 2 h of incubation & sustained nearly 50% of catalytic activity until the 9th repeated cycle of utilization. Moreover, immobilized trypsin retained 50% of enzymatic activity after 90 days of storage at 4 °C. Hence, the current findings suggest that ZnO/Chitosan-GA-Trypsin would be a promising biocatalyst for large-scale biotechnological applications.

A SiO2 Microcarrier with an Opal-like Structure for Cross-Linked Enzyme Immobilization

The opal-like SiO₂ microcarriers with different pore diameters named opal-SiO₂I and opal-SiO₂II were synthesized and utilized as microcarriers to immobilize Rhizopus oryzae lipase (ROL) and Aspergillus oryzae α-amylases (AOA). ROL and AOA can be more stably immobilized on the cross-linked SiO₂ opals by neopentyl glycol diglycidyl ether (NGDE), which is the first attempt to use it as a cross-linking agent compared with glutaraldehyde. According to the morphology analysis, multiple layers of SiO₂ monodisperse microspheres were regularly packed and formed an opal-like structure, and enzymes were well scattered and immobilized throughout the SiO₂ opals. The results showed that the performance of enzymes immobilized on opal-SiO₂II with a larger specific surface area was much better than that of opal-SiO₂I. The enzyme activity of ROL@opal-SiO₂II and AOA@opal-SiO₂II cross-linked with 1% NGDE increased 5.32 and 9.32 times compared with their free counterpart, respectively. Furthermore, pH and thermal stability and reusability of ROL/AOA@opal-SiO₂II were significantly improved and higher than those of ROL/AOA@opal-SiO₂I and free enzymes. This study provides an easily obtained microcarrier opal-SiO₂II, which shows potential for efficient different enzyme immobilizations and further industrial applications.

The bonding nature of the chemical interaction between trypsin and chitosan based carriers in immobilization process depend on entrapped method: A review

The review article is dedicated to a comprehensive study of the chemical bond formed during the immobilization of the proteolytic enzyme pancreatic trypsin in chitosan-based polymer matrixes and its derivatives. The main focus of the study is to describe the chemical bond that causes immobilization between chitosan based carriers and trypsin. Because the nature of the chemical bond between the carrier and trypsin is a key factor in determining the area of application of the conjugate. It has been found out that after the chemical nature of functional groups, their degree of ionization, the structure of the chemical cross-linking, the medium pH and ionic strength of chitosan are modified, the mechanism of trypsin immobilization is affected. As a result, the attraction enzyme to the matrix occurs due to polar covalent and hydrogen bonds, as well as electrostatic, hydrophobic, Van der Waals forces. The collected research works on the immobilization of trypsin on chitosan-based carriers have been systematized in the paper and shown schematically in subsystems according to the type of chemical interaction. It has been shown that the immobilization of trypsin on chitosan based matrixes occur more often due to the covalent and hydrogen bonds between the protein and the carrier.

Immobilization of Trypsin from Porcine Pancreas onto Chitosan Nonwoven by Covalent Bonding

The present study deals with the potential application of chitosan nonwoven for biomedical textiles based on enzyme immobilization. For this, chitosan nonwoven was first cross-linked with glutaraldehyde to introduce aldehyde groups at optimal conditions. To immobilize the enzyme trypsin onto glutaraldehyde-pre-activated chitosan nonwoven, several parameters such as pH, enzyme concentration, and reaction times were investigated. In addition, the pH, thermal stability, storage stability, and reusability of immobilized trypsin were examined. We found that the optimal immobilization conditions for trypsin were pH 8.5, enzyme concentration of 8% (owf), and treatment time of 30 min. Trypsin was immobilized at 25 °C efficiently. The immobilized trypsin showed lower pH stability and better thermal stability than free trypsin. The immobilized trypsin showed 50% of its initial activity after being used 15 times and 80% of that after 20 days of storage at 4 °C. SEM analysis also confirmed that trypsin was immobilized on chitosan nonwoven.

Improved cell membrane bioaffinity sample pretreatment technique with enhanced stability for screening of potential allergenic components from traditional Chinese medicine injections

Aiming at improving reliability in conventional cell membrane chromatography, an improved bioaffinity sample pretreatment technique with enhanced stability was developed to fast screen and extract potential allergenic components from traditional Chinese medicine injections.

Carbon nanotube filled with magnetic iron oxide and modified with polyamidoamine dendrimers for immobilizing lipase toward application in biodiesel production

Superparamagnetic multi-walled carbon nanotubes (mMWCNTs) were prepared by filling multi-walled carbon nanotubes (MWCNTs) with iron oxide, and further modified by linking polyamidoamine (PAMAM) dendrimers (mMWCNTs-PAMAM) on the surface. Then, mMWCNTs-PAMAM was employed as the carrier and successfully immobilized Burkholderia cepacia lipase (BCL) via a covalent method (BCL-mMWCNTs-G3). The maximum activity recovery of the immobilized lipase was 1,716% and the specific activity increased to 77,460 U/g-protein, 17-fold higher than that of the free enzyme. The immobilized lipase displayed significantly enhanced thermostability and pH-resistance, and could efficiently catalyze transesterification to produce biodiesel at a conversion rate of 92.8%. Moreover, it possessed better recycling performance. After 20 cycles of repeated used, it still retained ca. 90% of its original activity, since the carbon nanotube-enzyme conjugates could be easily separated from the reaction mixture by using a magnet. This study provides a new perspective for biotechnological applications by adding a magnetic property to the unique intrinsic properties of nanotubes.

Inorganic materials as supports for covalent enzyme immobilization: methods and mechanisms

Several inorganic materials are potentially suitable for enzymatic covalent immobilization, by means of several different techniques. Such materials must meet stringent criteria to be suitable as solid matrices: complete insolubility in water, reasonable mechanical strength and chemical resistance under the operational conditions, the capability to form manageable particles with high surface area, reactivity towards derivatizing/functionalizing agents. Non-specific protein adsorption should be always considered when planning covalent immobilization on inorganic solids. A huge mass of experimental work has shown that silica, silicates, borosilicates and aluminosilicates, alumina, titania, and other oxides, are the materials of choice when attempting enzyme immobilizations on inorganic supports. More recently, some forms of elemental carbon, silicon, and certain metals have been also proposed for certain applications. With regard to the derivatization/functionalization techniques, the use of organosilanes through silanization is undoubtedly the most studied and the most applied, although inorganic bridge formation and acylation with selected acyl halides have been deeply studied. In the present article, the most common inorganic supports for covalent immobilization of the enzymes are reviewed, with particular focus on their advantages and disadvantages in terms of enzyme loadings, operational stability, undesired adsorption, and costs. Mechanisms and methods for covalent immobilization are also discussed, focusing on the most widespread activating approaches (such as glutaraldehyde, cyanogen bromide, divinylsulfone, carbodiimides, carbonyldiimidazole, sulfonyl chlorides, chlorocarbonates, N-hydroxysuccinimides).

Covalent immobilization of mixed proteases, trypsin and chymotrypsin, onto modified polyvinyl chloride microspheres

A commercially available trypsin-chymotrypsin mixture was covalently immobilized onto modified polyvinyl chloride (PVC) microspheres, which were activated by the subsequent treatment of PVC microspheres with ethylenediamine and glutaraldehyde. The immobilized mixed protease was characterized by FT-IR and SEM analyses. Immobilization conditions were optimized by Box-Behnken design and the response surface method. The activity of the immobilized mixed protease prepared under optimal conditions (pH 6.6, 23 °C, 2 h) reached 1341 U/g. Compared with the free form, the immobilized enzyme possesses a slightly higher optimal pH value and a wider pH-activity profile, superior thermal stability, and a higher Km value. Reusability of the immobilized mixed protease indicated that >70% of the original activity was retained after having been recycled six times.

One-pot solvothermal synthesis of highly water-dispersible size-tunable functionalized magnetite nanocrystal clusters for lipase immobilization

A facile one-pot synthesis of highly water-dispersible size-tunable magnetite (Fe3O4) nanocrystal clusters (MNCs) end-functionalized with amino or carboxyl groups by a modified solvothermal reduction reaction has been developed. Dopamine and 3,4-dihydroxyhydroxycinnamic acid were used for the first time as both a surfactant and interparticle linker in a polylol process for economical and environment-friendly purposes. Morphology, chemical composition, and magnetic properties of the prepared particles were investigated by several methods, including FESEM, TEM, XRD, XPS, Raman, FTIR, TGA, zeta potential, and VSM. The sizes of the particles could be easily tuned over a wide range from 175 to 500 nm by varying the surfactant concentration. Moreover, ethylene glycol/diethylene glycol (EG/DEG) solvent mixtures with different ratios could be used as reductants to obtain the particles with smaller sizes. The XRD data demonstrated that the surfactants restrained the crystal growth of the grains. The nanoparticles showed superior magnetic properties and high colloidal stability in water. The cytotoxicity results indicated the feasibility of using the synthesized nanocrystals in biology-related fields. To estimate the applicability of the obtained MNCs in biotechnology, Candida rugosa lipase was selected for the enzyme immobilization process. The immobilized lipase exhibited excellent thermal stability and reusability in comparison with the free enzyme. This novel strategy would simplify the reaction protocol and improve the efficiency of materials functionalization, thus offering new potential applications in biotechnology and organocatalysis.

Thermostable trypsin conjugates immobilized to biogenic magnetite show a high operational stability and remarkable reusability for protein digestion

In this work, magnetosomes produced by microorganisms were chosen as a suitable magnetic carrier for covalent immobilization of thermostable trypsin conjugates with an expected applicability for efficient and rapid digestion of proteins at elevated temperatures. First, a biogenic magnetite was isolated from Magnetospirillum gryphiswaldense and its free surface was coated with the natural polysaccharide chitosan containing free amino and hydroxy groups. Prior to covalent immobilization, bovine trypsin was modified by conjugating with α-, β- and γ-cyclodextrin. Modified trypsin was bound to the magnetic carriers via amino groups using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide and N-hydroxysulfosuccinimide as coupling reagents. The magnetic biomaterial was characterized by magnetometric analysis and electron microscopy. With regard to their biochemical properties, the immobilized trypsin conjugates showed an increased resistance to elevated temperatures, eliminated autolysis, had an unchanged pH optimum and a significant storage stability and reusability. Considering these parameters, the presented enzymatic system exhibits properties that are superior to those of trypsin forms obtained by other frequently used approaches. The proteolytic performance was demonstrated during in-solution digestion of model proteins (horseradish peroxidase, bovine serum albumin and hen egg white lysozyme) followed by mass spectrometry. It is shown that both magnetic immobilization and chemical modification enhance the characteristics of trypsin making it a promising tool for protein digestion.

Preparation of superparamagnetic Fe3O4@alginate/chitosan nanospheres for Candida rugosa lipase immobilization and utilization of layer-by-layer assembly to enhance the stability of immobilized lipase

Superparamagnetic alginate nanospheres with diameter of 50 nm were prepared by self-assembly of alginate in the Ca(2+) solution; and then superparamagnetic alginate/chitosan nanospheres, which have positive charge and could adsorb lipase directly, were obtained with a following assembly of chitosan based on the electrostatic interaction between alginate and chitosan. Subsequently, oxidic poly (ethylene glycol) was used to functionalize the magnetic alginate/chitosan nanospheres. Thus, the magnetic nanospheres with aldehyde groups and a brushlike structure were formed. With various characterizations, it was verified that the magnetic alginate/chitosan nanospheres held small diameters (around 60 nm) and displayed superparamagnetism with high saturation magnetization. The Candida rugosa lipase (CRL), meanwhile, was immobilized onto the magnetic alginate/chitosan nanospheres by electrostatic adsorption and covalent bonding, respectively. Afterward, a layer-by-layer (LBL) assembly process was utilized to coat the immobilized CRL (ICRL) with covering layers made up of alginate and chitosan. After studying the properties of ICRL such as activity, kinetic behaviors, stability and reusability, it was proved that the ICRL prepared with two methods displayed more excellent properties than that prepared with electrostatic adsorption only. Additionally, coating ICRL with covering layers showed good effect on improving the stability of ICRL.

Covalent immobilisation of protease and laccase substrates onto siloxanes

Immobilisation of enzyme substrates is a powerful tool in the detection of enzymes in the chemosphere and the environment. A siloxane based strategy for the covalent immobilisation of oxidoreductase and protease substrates was developed involving activation of silica gel and polyethylene terephthalate (PET) as model carriers with (3-aminopropyl)-triethoxysilane or (3-mercaptopropyl)-trimethoxysilane (APTS, MPTS). Ferulic acid and L-Leucine-p-nitroanilide, Gly-Phe p-nitroanilide (GPpNA) and N-Succinyl-Ala-Ala-Pro-Leu p-nitroanilide (SAAPLpNA) as laccase and protein substrates, respectively, were covalently attached using glutaraldehyde or carbodiimide based cross-linking strategies. In contrast to conversion in solution, immobilised SAAPLpNA was hydrolysed much faster by protease than immobilised GPpNA indicating steric hindrance with decreasing chain length between point of attachment and site of enzyme attack. Immobilised ferulic acid was oxidised by laccase both in case of MPTS and APTS-modified silica gel giving clearly visible colour changes with Delta E values of 7.2 and 2.3, respectively after 24h of incubation, where Delta E describes the distance between two colours. Similarly, clearly visible colour changes with a Delta E value of 8.6 were seen after laccase treatment of ferulic acid immobilised on APTS activated PET as carrier. Limited surface hydrolysis of PET with a cutinase enhanced coupling of APTS and ferulic acid due to a larger number of hydroxyl groups available on the surface and consequently led to a higher colour difference of Delta E=12.2 after laccase oxidation. The covalent coupling product between ferulic acid and 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane was identified by LC-MS (M+1m/z601) and successfully oxidised with laccase.

Development of an automated digestion and droplet deposition microfluidic chip for MALDI-TOF MS

An automated proteolytic digestion bioreactor and droplet deposition system was constructed with a plastic microfluidic device for off-line interfacing to matrix assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The microfluidic chips were fabricated in poly(methyl methacrylate) (PMMA), using a micromilling machine and incorporated a bioreactor, which was 100 microm wide, 100 microm deep, and possessed a 4 cm effective channel length (400 nL volume). The chip was operated by pressure-driven flow and mounted on a robotic fraction collector system. The PMMA bioreactor contained surface immobilized trypsin, which was covalently attached to the UV-modified PMMA surface using coupling reagents N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride (EDC) and hydroxysulfosuccinimide (sulfo-NHS). The digested peptides were mixed with a MALDI matrix on-chip and deposited as discrete spots on MALDI targets. The bioreactor provided efficient digestion of a test protein, cytochrome c, at a flow rate of 1 microL/min, producing a reaction time of approximately 24 s to give adequate sequence coverage for protein identification. Other proteins were also evaluated using this solid-phase bioreactor. The efficiency of digestion was evaluated by monitoring the sequence coverage, which was 64%, 35%, 58%, and 47% for cytochrome c, bovine serum albumin (BSA), myoglobin, and phosphorylase b, respectively.

Silica gel functionalized with 4-phenylacetophynone 4-aminobenzoylhydrazone: Synthesis of a new chelating matrix and its application as metal ion collector

The silica gel surface immobilized with 4-phenylacetophynone 4-aminobenzoylhydrazone (PAAH) after surface modification by 3-chloropropyltrimethoxysilane (CPTS). The modified silica gel was used for sorption of Cu(II), Ni(II) and Co(II) in aqueous solution. The effect of solution pH, sorption time, temperature and initial metal ion concentration onto metal ions sorption was investigated. The characteristics of the sorption process were evaluated by using the Langmuir, Freundlich and Dubinin-Radushkevich (D-R) adsorption isotherms. The sorption of metal ions onto modified silica gel correlated well with the Langmuir type adsorption isotherm and adsorption capacities were found to be 0.012, 0.014 and 0.018 mmol g(-1) for Cu(II), Ni(II) and Co(II) metal ions, respectively. From the D-R adsorption isotherms, it was concluded that chemical interactions and chelating effects were playing an important role in the sorption of metal ions onto modified silica gel. Thermodynamic parameters such as the standard free energy change (DeltaG) degrees , enthalpy change (DeltaH degrees ) and entrophy change (DeltaS degrees ) were calculated to determine the nature of sorption process. From these parameters, DeltaH degrees were found to be endothermic values: 38.39, 18.0, and 14.7 kJ mol(-1) for the same sequence of divalent cations and DeltaS degrees values were calculated to be positive for the sorption of each metal ion onto the modified silica gel. Negative DeltaG degrees values indicated that sorption process for all metal ions were spontaneous in nature although they presented an endothermic enthalpy for the interaction, resulting in an entropically favoured process.

Application and properties of butyl acrylate/pentaerythrite triacrylate copolymers and cellulose-based Granocel as carriers for trypsin immobilization

The main point was the search for a proper carrier and the kind of carrier activation for trypsin (EC 3.4.21.4) immobilization. The acrylic and cellulose-based carriers were specially prepared in that they possessed the most often used anchor groups: -OH, -NH(2), DEAE and/or -COOH. The immobilization procedures were selected to apply mainly to protein amine groups and appropriate anchor groups on the carrier. As activity tests low (N-benzoyl-dl-arginine-p-nitroanilide, BAPNA) and high (casein) molecular weight substrates were used. It was found, as a rule, that trypsin bound to -COOH groups with the help of carbodiimide was less active and that the amount of bound protein and measured activity (BAPNA) are considerably higher when protein is immobilized via divinyl sulfone. Both rules were observed irrespective of the nature of the polymer matrix. Both types of carriers were found suitable for trypsin immobilization and they were far better than the corresponding Eupergit C-bound enzyme preparations. Taking into account storage stability and activity for both substrates, the divinylsulfone linkage formed between unmodified Granocel and trypsin was the most effective method for the enzyme immobilization. For this preparation, BAPNA and casein conversion, thermal stability at 60 degrees C and estimated kinetic parameters were compared with those obtained for the native enzyme. It was shown that mass transport limitations could be effectively eliminated by suitable conditions and immobilized trypsin was considerably more stable. The values k(cat)/K(m) indicated that the immobilized enzyme was even better as amidase activity was regarded and its potential for protein hydrolysis was only less than twice.