Application of dye-ligands affinity adsorbent in capturing of rabbit immunoglobulin G

The applicability of dye-ligands attached to an expanded bed chromatography quartz base matrix (Streamline™) for the affinity bioseparation of rabbit immunoglobulin G (IgG) was investigated. Reactive Green 5 (RG-5) immobilized onto adsorbent was selected for capturing of rabbit-IgG due to its higher binding capacity compared to other dye-ligands possessing similar ligand density. Adsorption parameters such as pH, temperature, ionic strength and initial rabbit-IgG concentration were optimized for the adsorption of rabbit-IgG on the RG-5-immobilized adsorbent. The highest rabbit-IgG adsorption was recorded in pH 7.0, while the maximum binding capacity for BSA was achieved at pH 4.0. The adsorption of rabbit-IgG on RG-5-immobilized adsorbent was declined as the increase of ionic strength. There is no significant influence of temperature against adsorption efficiency of RG-5-immobilized adsorbent for rabbit-IgG. The adsorption phenomenon of rabbit-IgG on RG-5-immobilized adsorbent appeared to follow the Langmuir–Freundlich adsorption isotherm model. The theoretically maximum binding capacity (q_m) of RG-5-immobilized adsorbent estimated from this isotherm was 49.3 mg ml⁻¹, which is very close to that obtained experimentally (49.0 mg ml⁻¹). About 50% of bound BSA on RG-5-immobilized adsorbent in binary adsorption system was removed with washing buffer containing 1 M NaCl.     

Preparation and characterization of mixed-mode magnetic adsorbent with p-amino-benzamidine ligand: Operated in a magnetically stabilized fluidized bed reactor for purification of trypsin from bovine pancreas

The magnetic beads were synthesized using glycidylmethacrylate (GMA) and methylmethacrylate (MMA) monomers. A multimodal ligand (i.e., p-amino-benzamidine) was covalently immobilized onto magnetic beads after glutaraldehyde activation, and consequently used for purification of the trypsin from bovine pancreas. The p-amino-benzamidine ligand immobilized magnetic beads were characterized by FTIR, VSM, SEM, and analytical methods. Trypsin adsorption experiments were investigated under different experimental conditions (i.e., medium pH, initial trypsin concentration, temperature, and ionic strength) in a batch system. Maximum trypsin adsorption capacity was found to be 75.9 ± 2.6 mg/g beads. Adsorbed trypsin was eluted by using (0.1 M acetate buffer, pH 3.0) with a 97% recovery. The purification factor of trypsin from crude pancreas extract was 8.7 folds. The purity of the eluted trypsin from p-amino-benzamidine functionalized magnetic beads was determined as 86% by HPLC. The method developed in this report was successfully applied for purification of the trypsin from crude pancreas extract in a magnetically stabilized fluidized bed reactor.     

Antibody purification with protein A attached supermacroporous poly(hydroxyethyl methacrylate) cryogel

Immunoglobulin G (IgG) purification from human plasma with protein A attached supermacroporous poly(hydroxyethyl methacrylate) [PHEMA] cryogel has been studied. PHEMA cryogel was prepared by bulk polymerization which proceeds in aqueous solution of monomer frozen inside a plastic syringe (cryo-polymerization). After thawing, the PHEMA cryogel contains a continuous matrix having interconnected pores of 10–200 μm size. Protein was covalently attached onto the PHEMA cryogel via cyanogen bromide (CNBr) activation. The maximum IgG adsorption on the PHEMA/protein A cryogel was found to be 83.2 mg/g at pH 7.4 from aqueous solutions. The non-specific IgG adsorption onto the PHEMA cryogel was about 0.38 mg/g. The macropore size of the cryogel makes it possible to process blood cells without blocking the column. Higher adsorption capacity was observed from human plasma (up to 88.1 mg/g). Adsorbed IgG was eluted using 0.1 M glycine–HCl buffer (pH 3.5) with a purity of 85%. PHEMA–protein A cryogel was used for repetitive adsorption/desorption of IgG without noticeable loss in IgG adsorption capacity after 10 cycles. PHEMA–protein A cryogel showed several advantages such as simpler preparation procedure, good selectivity for IgG purification from human plasma and good stability throughout repeated adsorption–desorption cycles.     

Molecular characterization of a novel soybean gene encoding a neutral PR-5 protein induced by high-salt stress

In this study, we characterized a novel soybean gene encoding a neutral PR-5 protein and compared it to two acidic isoforms of soybean PR-5 protein. This gene, designated as Glycine max osmotin-like protein, b isoform (GmOLPb, accession no. AB370233), encoded a putative protein having the greatest similarity to chickpea PR-5b (89% identity). Unlike the two acidic PR-5, GmOLPa and P21, the protein had a C-terminal elongation responsible for possible vacuolar targeting and after maturation showed a calculated molecular mass of 21.9 kDa with pI 6.0. The 3D models, predicted by the homology modeling, contained four α-helixes and 16 β-strands and formed three characteristic domains. The two acidic PR-5 proteins also showed a 3D structure very similar to GmOLPb, although the electrostatic potential on molecular surface of each PR-5 was significantly different. In the study of the gene expression under conditions of high-salt stress, GmOLPb was highly induced in the leaves of the soybean, particularly in the lower part of a leaf. The expression started at 2 h after initiation of the stress and was highly induced between 18–72 h. Gene expression of P21e (protein homologous to P21) was transiently induced by high-salt stress, but took place earlier than the gene expressions of GmOLPa and GmOLPb. Such differential expression was observed also under investigation with methyl jasmonate and salicylic acid. These results suggested that each soybean PR-5 might play a distinctive role in the defensive system protecting the soybean plant against high-salt stress, particularly in the leaves of the soybean.     

Characterization,purification, and temperature/pressure stability of polyphenol oxidase extracted from plums (Prunus domestica)

In this study, polyphenol oxidase (PPO) was extracted from Prunus domestica and partially purified by ammonium sulfate precipitation, hydrophobic interaction chromatography, and ion exchange chromatography. The final purification step revealed a 32.81-fold purification, and the molecular mass was estimated to be 65 kDa by SDS-PAGE. The purified PPO showed enzymatic activity mainly toward five substrates, namely catechol, catechin, 4-methyl catechol, chlorogenic acid, and L-3,4-dihydroxyphenylalanine, whereas it showed no activity toward caffeic acid, ferulic acid, p-coumaric acid, p-cresol, and l-tyrosine. The optimum pH and temperature values were 6.0 and 25 °C, respectively. The enzyme showed high stability in the pH range of 5.0–7.0 and in the temperature range of 25–65 °C. The most effective inhibitors of this enzyme were found to be ascorbic acid and l-cysteine. The thermal inactivation followed a first-order kinetic model, with activation energy of E_a 150.46 ± 1.29 kJ/mol. PPO extracted from plum showed stability at high pressure, with enzyme activation at 500 MPa.     

Extraction and purification of a lectin from small black kidney bean (Phaseolus vulgaris) using a reversed micellar system

Lectin from crude extract of small black kidney bean (Phaseolus vulgaris) was successfully extracted using the reversed micellar extraction (RME). The effects of water content of organic phase (W_o), ionic strength, pH, Aerosol-OT (AOT) concentration and extraction time on the forward extraction and the pH and ionic strength in the backward extraction were studied to optimize the extraction efficiency and purification factor. Forward extraction of lectin was found to be maximum after 15 min of contact using 50 mM AOT in organic phase with W_o 27 and 10 mM citrate-phosphate buffer at pH 5.5 containing 100 mM NaCl in the aqueous phase. Lectin was backward extracted into a fresh aqueous phase using sodium-phosphate buffer (10 mM, pH 7.0) containing 500 mM KCl. The overall yield of the process was 53.28% for protein recovery and 8.2-fold for purification factor. The efficiency of the process was confirmed by gel electrophoresis analysis.     

Bacterial cellulose nanofibers for albumin depletion from human serum

Cibacron Blue F3GA (CB) was covalently attached onto the bacterial cellulose (BC) nanofibers for human serum albumin (HSA) depletion from human serum. The BC nanofibers were produced by Acetobacter xylinum in the Hestrin–Schramm medium in a static condition for 14 days. The CB content of the BC nanofibers was 178 μmol/g. The specific surface area of the BC nanofibers was determined to be 914 m²/g. HSA adsorption experiments were performed by stirred-batch adsorption. The non-specific adsorption of HSA on the BC nanofibers was very low (1.4 mg/g polymer). CB attachment onto the BC nanofibers significantly increased the HSA adsorption (1800 mg/g). The maximum HSA adsorption was observed at pH 5.0. The HSA adsorption capacity decreased drastically with an increase of the aqueous phase concentration of sodium chloride. The elution studies were performed by adding 1 M NaCl to the HSA solutions in which adsorption equilibria had been reached. The elution results demonstrated that the binding of HSA to the adsorbent was reversible. The depletion efficiencies for HSA were above 96.5% for all studied concentrations. Proteins in the serum and eluted portion were analyzed by SDS-PAGE for testing the efficiency of HSA depletion from human serum. Eluted proteins include mainly HSA.     

Integrated enzyme purification and immobilization processes with immobilized metal affinity adsorbents

Silica-based immobilized metal affinity chromatography adsorbents with various ligand densities were prepared for the purification and immobilization of poly(His)-tagged d-hydantoinase (DHTase). An adsorbent with a ligand density of 13.0 μmol Cu²⁺/g gel exhibiting the optimal selectivity and a capacity of 1.4 mg/g gel toward the poly(His)-tagged enzyme was identified. The adsorbent was used for the one-step purification of His-tagged enzymes from crude cell lysate with a purity above 90%. The silica-based affinity adsorbents are particularly well suited for industrial scale operations due to their robustness. A packed-bed bioreactor with the DHTase-loaded adsorbents was used for the continuous conversion of d,l-p-hydroxyphenylhydantoin (d,l-HPH) to N-carbamoyl-d-hydroxyphenylglycine, an intermediate for the production of d-hydroxylphenylglycine. Under optimal conditions, 60 °C and pH 8.0, a conversion of 60% was obtained at a residence time of 30 min. Upon extended operation, the catalytic activity of the biocatalysts declined significantly due to enzyme leakage and enzyme denaturation. The extent of enzyme leakage can be attenuated by crosslinking with glutaraldehyde. In this study, we successfully demonstrate that a packed-bed bioreactor containing silica-based IMAC adsorbents can be used for the direct purification and immobilization of poly(His)-tagged enzymes for biotransformation.     

Purification of human IgG by negative chromatography on ω-aminohexyl-agarose

The ω-aminohexyl diamine immobilized as ligand on CNBr- and bisoxirane-activated agarose gel was evaluated for the purification of human immunoglobulin G (IgG) from serum and plasma by negative affinity chromatography. The effects of matrix activation, buffer system, and feedstream on recovery and purity of IgG were studied. A one-step purification process using Hepes buffer at pH 6.8 allowed a similar recovery (69–76%) of the loaded IgG in the nonretained fractions for both matrices, but the purity was higher for epoxy-activated gel (electrophoretically homogeneous protein with a 6.5-fold purification). The IgG and human serum albumin (HSA) adsorption equilibrium studies showed that the adsorption isotherms of IgG and HSA obeyed the Langmuir–Freundlich and Langmuir models, respectively. The binding capacity of HSA was high (210.4 mg mL^?1 of gel) and a positive cooperativity was observed for IgG binding. These results indicate that immobilizing ω-aminohexyl using bisoxirane as coupling agent is a useful strategy for rapid purification of IgG from human serum and plasma.     

Separation of human Fab fragments on negative mode Ni(II)-TREN-agarose chromatography

We evaluated the feasibility of using immobilized metal-ion affinity chromatography (IMAC) with nickel ion complexed with Tris(2-aminoethyl)amine (TREN) immobilized on agarose gel for purification of human Fab fragments by negative chromatography. Efficient purification of Fab fragments from digested human IgG (immunoglobulin G) (106.4% purity) was accomplished in Tris-HCl buffer at pH 7.5 without NaCl (based on total protein concentration and radial immunodiffusion of human Fab). A technological application of Ni(II)-TREN-agarose using non transgenic soybean protein extract spiked with human Fab fragments as feedstream was also studied. Experiments using Tris-HCl at pH 7.0 as loading buffer allowed the adsorption of almost all of the soybean proteins. Sixty-six percent of the loaded human Fab fragments were recovered in the flowthrough and washing fractions with about 90% purity. These results demonstrate that Ni(II)-TREN-agarose is a potential adsorbent for recombinant Fab fragment purification.     

Dye–ligand expanded bed adsorption of G6PDH from highly dense unclarified yeast extract

The application of dye–ligand expanded bed chromatography adsorption (EBA) of glucose-6-phosphate dehydrogenase (G6PDH) from unclarified yeast extract was undertaken by using a commercially available expanded bed column (20 mm i.d.) and UpFront adsorbent (ρ = 1.5 g/mL) from UpFront Chromatography. The influence of biomass concentration on the adsorption capacity was explored by employing yeast extracts containing various biomass concentrations (5–30%, w/v). It was demonstrated that the biomass concentration had little effect on G6PDH adsorption performance. Feedstock containing 15% (w/v) biomass gave a relatively high recovery yield (>90%) of G6PDH compared to feedstock containing 30% (w/v) biomass, which gave a recovery of 75% G6PDH. Nevertheless, the enzyme specific activity of 7 U mg⁻¹ with a purification factor of 6 was achieved in the feedstock containing biomass concentration of 30% (w/v). The generic applicability of dye–ligand as an affinity tool in expanded bed chromatography is discussed.     

Synthesis of thermo-sensitive copolymer with affinity butyl ligand and its application in lipase purification

In this study, thermo-sensitive N-alkyl substituted polyacrylamide polymer P_NNB was synthesized by using N-hydroxymethyl acrylamide(NHAM), N-isopropyl acrylamide (NIPA) and butyl acrylate (BA) as monomers, and its low critical solution temperature (LCST) was controlled to be 28 °C. The recovery of the thermo-sensitive polymer was over 98%. Butanol as a hydrophobic ligand was covalently attached onto polymer P_NNB and butyl ligand density was 80 μmol g^?1 polymer. The affinity polymer was used for purification of lipase from crude material. Optimized condition was pH 7.0, 35 °C adsorption temperature, 120 min adsorption time and 0.5 mg ml^?1 initial concentration of lipase. The adsorption isotherm accords with a typical Langmuir isotherm. The maximum adsorption capacity (Q_m) of the affinity polymer for lipase was 24.8 mg g^?1polymer. The affinity copolymer could be recycled by temperature-inducing precipitation and there was only about 6% loss of adsorption capacity after five recyclings. Specific activity of lipase was improved from 14 IU mg^?1 to 506 IU mg^?1 protein, and its recovery achieved 82%. The affinity polymer is suitable for the purification of target proteins from the crude material with large volume and dilute solution.     

Synthesis of thermo-sensitive polyacrylamide derivatives for affinity precipitation and its application in purification of lysozyme

The thermo-sensitive N-alkyl substituted polyacrylamide polymer was synthesized by radical polymerization and its lower critical solution temperature (LCST) was controlled to be 28 °C. The thermo-sensitive recovery of polymer was over 95% in the presence of 0.05 M NaClO₄. Cibacron Blue F3GA was covalently immobilized onto the polymer via the nucleophilic reaction between the active chlorine atom of its triazine ring and the hydroxyl group of the polymer. The ligands density was 30 μmol g⁻¹ polymer. The adsorption capacity of lysozyme on the polymer was 3.4 mg g⁻¹polymer in affinity precipitation process. And over 90% of adsorbed lysozyme was eluted by 0.5 M KSCN at pH 8.0. When the affinity polymer was applied in the purification of lysozyme from egg white, the purification factor was 28 and lysozyme yield was 80% or so.     

The harnessing of peptide–monolith constructs for single step plasmid DNA purification

The availability of synthetic peptides has paved the way for their use in tailor-made interactions with biomolecules. In this study, a 16mer LacI-based peptide was used as an affinity ligand to examine the scale up feasibility for plasmid DNA purification. First, the peptide was designed and characterized for the affinity purification of lacO containing plasmid DNA, to be employed as a high affinity ligand for the potential capturing of plasmid DNA in a single unit operation. It was found there were no discernible interactions with a control plasmid that did not encode the lacO nucleotide sequence. The dissociation equilibrium constant of the binding between the 16mer peptide and target pUC19 was 5.0 ± 0.5 × 10⁻⁸ M as assessed by surface plasmon resonance. This selectivity and moderated affinity indicate that the 16mer is suitable for the adsorption and chromatographic purification of plasmid DNA. The suitability of this peptide was then evaluated using a chromatography system with the 16mer peptide immobilized to a customized monolith to purify plasmid DNA, obtaining preferential purification of supercoiled pUC19. The results demonstrate the applicability of peptide–monolith supports to scale up the purification process for plasmid DNA using designed ligands via a biomimetic approach.     

Rapid cloning,expression and purification of a novel high-activity alkaline phosphatase with detoxification of lipopolysaccharide

Lipopolysaccharide (LPS) is a bacterial endotoxin leading to endotoxemia. Its virulence factor ‘diphosphoryl lipid A’ can be abolished by alkaline phosphatase (AP). A novel AP gene (without introns) was cloned from Saccharomyces boulardii ATCC MYA-796 with a GenBank accession number KF471017, and the recombinant AP (rAP) was expressed as a soluble protein in Pichia pastoris X-33 with a yield of 43.66 mg/l at the end of 120 h of induction in a shaker flask. After purification by affinity-column chromatography, the purity of rAP was over 90%. The optimal reaction conditions of rAP were pH 9.6, temperature at 60 °C and 2 mM Mg²⁺ in diethanolamine buffer, and EDTA was a potent inhibitor of rAP activity. The specific activity of rAP was 9912.01 U/mg under the optimal conditions. Furthermore, rAP showed a broad dephosphorylation activity to LPS over a broad pH range (pH 2–10) in vitro and peaked at pH 4 in Tris–HCl buffer. After LPS dephosphorylated by rAP was injected intraperitoneally into mice, the serum level of tumor necrosis factor (TNF)-α was significantly reduced compared to that of the LPS group (p < 0.01). These findings suggest that rAP has great potential to cure diseases caused by LPS.     

Partial purification and characterization of Helicoverpa armigera (Lepidoptera: Noctuidae) active aminopeptidase secreted in midgut

We report the partial purification to apparent homogeneity of a soluble aminopeptidase (EC 3.4.11.1) from midgut of Helicoverpa armigera larvae, which preferentially degraded Leucine p-nitroanilide (LpNA). After midgut isolation, extraction and precipitation of soluble proteins with acetone, proteins were purified in two consecutive steps including gel filtration and ion-exchange chromatographies. Aminopeptidase activity was increased 8.95 fold after gel filtration chromatography. The purified enzyme appeared as single band with a molecular mass of ～ 112 kDa in SDS-PAGE, with a pH optimum of 7.0. Zymogram analysis revealed two enzymatically active proteinases using LpNA as substrate. The optimal temperature of aminopeptidase activity was 50–60 °C. The enzyme was characterized as metalloprotease as it was strongly inhibited by 1,10 phenanthroline. Strong inhibition was also being observed using the specific aminopeptidase inhibitor bestatin. Heavy metal ions, EDTA and cysteine strongly inhibited the enzyme, while Ca^+ 2, Mn^+ 2 and Mg^+ 2 somewhat stimulated aminopeptidase activity. Besides LpNA, the purified aminopeptidase also cleaved with decreasing activity ApNA, VpNA and BApNA. Study could be helpful to understand the mechanism of action of N-terminal degrading enzymes and also important is to further study the differential interaction of Bacillus thuringiensis cry insecticidal toxin with midgut receptor of insects.     

Enhanced biotransformation of l-phenylalanine to 2-phenylethanol using an in situ product adsorption technique

An in situ product adsorption technique was used to enhance the biotransformation of l-phenylalanine to 2-phenylethanol by Saccharomyces cerevisiae BD. As a suitable adsorbent, the non-polar macroporous resin D101, selected from several resins tested, showed high adsorption capacity for 2-phenylethanol but not l-phenylalanine. Product inhibition was effectively alleviated by the addition of macroporous resin D101 to the biotransformation medium. When 2 g of hydrated resin D101 was added to 30 mL of the biotransformation medium, the total 2-phenylethanol concentration achieved was 6.17 g/L, of which 3.15 g/L remained in the aqueous phase and 3.02 g/L was adsorbed onto the resin. The molar yield of 2-phenylethanol reached 0.70 after 24 h cultivation. Addition of the macroporous resin greatly increased the volumetric productivity of 2-phenylethanol, and made the downstream processing more feasible and easier to perform in an industrial application.     

Biochemical characterization of an effective substrate and potent activators of CK2 copurified with Bowman-Birk-type proteinase inhibitor from soybean seeds in vitro

By means of Mono P column chromatography, an effective phosphate acceptor (EPA) of casein kinase 2 (CK2) was purified from the Bowman-Birk-type proteinase inhibitor (BBI) fraction of soybean seeds. The most acidic EPA (aEPA, pI = approx. 3.7) was heavily phosphorylated when incubated with CK2 and 5 μM [γ-³²P]ATP in the presence of poly-Arg (a CK2 activator) in vitro. However, aEPA was slightly phosphorylated by casein kinase 1 (CK1) as effective as C-kinase and not at all by A-kinase in vitro. The 13 N-terminal amino acid residues (SDHSSSDDESSKP) of aEPA were 100% homologous to the corresponding sequence of soybean BBI-type proteinase inhibitor CII (SBI CII). Polyamine at 3 mM stimulated 4.6-fold the CK2-mediated phosphorylation of aEPA, and this phosphorylation was sensitive to quercetin (ID₅₀ = approx. 0.1 μM) in vitro. Furthermore, two basic proteins [Mr = 29,000 (p29) and 17,000 (p17)] copurified with BBI were identified as proteolytic cleavage products of basic 7S globulin and functioned as potent CK2 activators in vitro. aEPA fully phosphorylated by CK2 in the presence of poly-Arg or basic proteins formed a complex with trypsin, whereas unphosphorylated aEPA was digested by trypsin in vitro. These results suggest that (i) aEPA (a BBI isoform) may coexist with two basic proteins (p29 and p17) generated from basic 7S globulin; and (ii) the physiological interaction between aEPA and its binding trypsin-like proteinases may be regulated through specific phosphorylation of aEPA by CK2 activated with the two basic proteins in legume seeds.     

Purification and properties of enantioselective lipase from a newly isolated Bacillus cereus C71

A lipase from Bacillus cereus C71 was purified to homogeneity by ammonium sulfate precipitation, followed by Phenyl-Sepharose chromatography, DEAE ion exchange chromatography and CIM^® QA chromatography. This purification procedure resulted in a 1092-fold purification of lipase with 18% yield. The molecular mass of the purified enzyme was determined to be approximately 42 kDa by SDS-PAGE and mass spectrometer. The lipase was stable in the pH range of 8.5–10.0, with the optimum pH 9.0. The enzyme exhibited maximum activity at 33 °C and retained 92% of original activity after incubation at 35 °C for 3 h. The protein hydrolyzed p-nitrophenyl esters with acyl chain lengths between C4 and C12. Enzyme activity was strongly inhibited in the presence of Cu²⁺ and Zn²⁺ but promoted by non-ionic surfactants. The lipase demonstrated higher enantioselectivity toward R-isomer of ethyl 2-arylpropanoate than the commercial lipases, and can be used potentially as a catalyst to prepare optically pure pharmaceuticals.