Production of low methoxyl pectin using immobilized pectinmethylesterase silica from acerola (Malpighia glabra L.)

The aim of this work was to develop an efficient reactor for the production of low methoxyl pectin, using pectinmethylesterase (PME, EC 3.1.1.11) from acerola immobilized on silica. The immobilized enzyme was used in up to 50 successive bioconversion runs at 50 °C with an efficiency loss of less than 20%. The fixed‐bed reactor (6.0 × 1.5 cm) was prepared using PME immobilized in glutaraldehyde‐activated silica operated at 50 °C with an optimum flow rate of 10 mL h^?1. The bioconversion yield was shown to strongly depend on the nature of the enzymatic preparation. An efficiency of 44% was achieved when concentrated PME was used, compared with only 30% with purified PME, both after an 8‐h run. The process described could provide the basis for the development of a commercial‐scale process. Copyright © 2006 Society of Chemical Industry     

Crosslinked poly(vinyl alcohol) supports for the immobilization of a lipolytic enzyme

Different esters of crosslinked poly(vinyl alcohol) (PVA) were synthetized. They were developed for protein fractionation and immobilization. PVA was crosslinked with epichlorohydrin (CL‐PVA) and esterified with linear fatty acids of different length (Cn‐CL‐PVA). A characterization of the obtained products was made. The swelling behavior, the solubility, and the percentage of esterification were examined. Values of equilibrium water content of about 81% were reached for CL‐PVA samples. The polymers' stability and morpholgy were also investigated. Thermal analysis showed an increase in matrices stability, while SEM data showed the superficial development due to crosslinking and esterification reactions. Moreover, evident morphological inhomogeneities, mainly in the commercial and crosslinked products rather than in the final polymer, were present. Finally, immobilization experiments with a commercial crude of Candida rugosa were performed. Experiments showed a greater affinity of the protein for carbon chain length ranging from 8 to 12. Data indicated that compared to Celite 545, C8‐CL‐PVA was a better support for enzyme immobilization by physical adsorption, confirming the fact that microbial lipases prefer hydrophobic supports. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1881–1889, 1999     

Evaluation of nanogels as supports for enzyme immobilization

Nanogels are hydrophilic polymers made up of crosslinked nano‐sized particles. These nanogels have large surface area that offers several functional groups as reserves for binding drugs, generating biosensors and as supports for enzyme immobilization. This mini‐review is an attempt to evaluate the recent developments in the use of nanogels as supports in enzyme immobilization. Emphasis is laid on the effect of nanogel structure and immobilization protocol on the property profile of the immobilized enzymes as compared with their free counterparts. The prospective applications of the nanogel‐immobilized enzymes are also evaluated. © 2014 Society of Chemical Industry     

Pectinlyase immobilization on epoxy supports for application in the food processing industry

The immobilization of a pectinlyase (PL, EC 4.2.2.3) contained in a commercial enzymic preparation was studied in view of its use for fruit pulp and juice processing. Two epoxy supports were tested for immobilization. These included Eupergit C (Rohm), a synthetic polymer, and γ-alumina functionalized with γ-glycidoxypropyltrimethoxysilane. In both biocatalysts, the catalytic response was not found to be high. The highest response in terms of immobilization yield and immobilized PL activity, however, was reported for Eupergit C (approx. 115 unit g^?1 at optimum pH).     

Microwave‐assisted immobilization of lipase from Candida rugosa on Eupergit® supports

BACKGROUND: Immobilization of lipase (triacylglycerol acylhydrolase EC 3.1.1.3) from Candida rugosa on Eupergit^® C and Eupergit^® C 250L was performed under microwave irradiation in order to reduce immobilization time. Lipase loading, hydrolytic activity, esterification activity and operational stability in organic solvent of immobilized lipase preparation were determined. RESULTS: The microwave‐assisted procedure resulted in a 29% lower lipase loadings, compared with immobilized lipase obtained without microwaves. In hydrolytic activity assay, lipase immobilized under microwaves exhibited a 23% higher specific activity. Slight activation of lipase by microwave‐assisted immobilization was observed, since specific activity was around 5% higher than for free lipase. Lipase of highest activity was obtained after 2 min immobilization on Eupergit^® C. The same preparation exhibited high esterification activity in organic medium and a half life of 212 h was determined in multiple use assay. CONCLUSION: The application of microwave irradiation leads to reduction of immobilization time from 2 days to only 2 min. The immobilized lipase obtained has prospects for further application due to its high retained activity and stability. Copyright © 2009 Society of Chemical Industry     

A simple rate model for the dynamics of immobilization of anaerobic bacteria on a plastic support

The dynamics of biofilm formation on polyethylene bioparticles in mesophilic anaerobic conditions, using an inverse fluidized bed as immobilization system, have been studied. The immobilization process was carried out using acetate and glucose as carbon sources. Scanning electron microscopy (SEM) showed cocci cells and Methanosaeta rods embedded into an exopolimeric substances (ESP) matrix. The acetoclastic activity was found to increase as soon as the lag biomass accumulation phase ended. The rate of immobilization was found to conform to a pseudo first order kinetics with good correlation. This kinetic model was used to estimate rate and equilibrium constants for the immobilization process. Rate properties have been explained in terms of attachment and detachment processes. © 2000 Society of Chemical Industry     

CYPHOS IL 101 (Tetradecyl(Trihexyl)Phosphonium Chloride) Immobilized in Biopolymer Capsules for Hg(II) Recovery from HCl Solutions

Abstract

A composite polymer (made of gelatin and alginate) was used for the synthesis of Cyphos IL 101-immobilized resins. These resins (with varying size and different ionic liquid (IL) content) have been tested for the recovery of mercury from concentrated HCl solutions (0.1–5 M HCl concentrations). Prior to the study of sorption performance on resins, the reactivity of Cyphos IL 101 versus mercury was tested using solvent extraction methodology. These results showed that the extraction was hardly affected by the concentration of HCl and that an ion exchange mechanism was probably involved in metal recovery (binding of HgCl₄ ^2-). The performance of these resins for Hg(II) recovery was tested through sorption isotherms and uptake kinetics, investigating the effect of resin size, ionic liquid content, metal concentration, agitation speed, and resin state (dry state versus wet state). Sorption capacity (which was proportional to the IL content) can reached up to 150 mg Hg g^?1 in 1 M HCl; this sorption capacity was decreased by increasing chloride concentration. The kinetics were described well by the pseudo-second order equation and by the intraparticle diffusion equation (the so-called Crank's equation). The intraparticle diffusion coefficient was in the range of 10^?11–1.2 × 10^?10 m² min^?1. The kinetic profiles were controlled by the IL content, sorbent dosage, and the sorbent particle size. Drying of the resins significantly decreased diffusion rates in the resins. The presence of competitor metals did not affect sorption capacity except when stable chloro-anionic species such as in the case of Zn(II) were formed. Mercury can be desorbed using 6 M nitric acid solutions; and the sorbent can be recycled for at least six sorption/desorption cycles without significant decrease in the sorption performance.     

Uniform poly(isopropylacrylamide) gel beads for immobilization of α-chymotrypsin

In this study, α-chymotrypsin was immobilized via physical entrapment within large, uniformly spherical, and thermally reversible poly(N-isopropylacrylamide) [poly(NIPAM)] beads. The gel beads were prepared in an aqueous dispersion medium by using Ca-alginate gel as the polymerization mold. In this preparation, potassium persulfate/tetramethylethylenediamine and sodium-alginate/calcium chloride were used as the redox initiator and the stabilizer systems, respectively. Thermoresponsive poly(NIPAM) gel beads 3 mm in size and including α-chymotrypsin were produced by the proposed procedure. The use of an aqueous bead-forming medium did not cause significant enzyme leakage during the preparation of enzyme-gel beads. Michaelis–Menten kinetics was used to define the behaviors of enzyme-gel beads prepared with different enzyme loadings. The Lineweaver–Burk plot indicated that the enzyme-gel system had a reasonably higher K_m value relative to that of free enzyme due to the internal mass transfer resistance against the substrate diffusion. The enzyme-gel system exhibited the maximum activity at 30°C due to the thermoresponsive character of the carrier matrix. However, the maximum activity with the free enzyme was observed at 40°C. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1127–1139, 1998     

Cinnamic ester of D‐sorbitol for immobilization of mushroom tyrosinase

Mushroom tyrosinase was immobilized by adsorption onto the totally cinnamoylated derivative of D ‐sorbitol. The polymerization and cross‐linking of the derivative initially obtained was achieved by irradiation in the ultraviolet region, where this prepolymer shows maximum sensitivity. Immobilization of tyrosinase on this support involves a process of physical adsorption and intense hydrophobic interactions between the cinnamoyl groups of the support and related groups of the enzyme. The pH value, enzyme concentration and immobilization time were all important parameters affecting immobilization efficiency; also, enzyme immobilization efficiency correlated well with the tyrosinase isoelectric point. The immobilized enzyme showed an optimum measuring pH of 3.5 and greater activity at acid and neutral pH values than the soluble enzyme. The optimal reaction temperature was 35 °C and the temperature profile was broader than that of the free enzyme or of the enzyme immobilized on other supports. The apparent Michaelis constant of mushroom tyrosinase immobilized on the SOTCN derivative acting on 4‐tert‐butylcatechol (TBC) was 0.40 ± 0.02 mmol dm^?3, which was lower than for the soluble enzyme, suggesting that the affinity of this enzyme for this substrate was greater when immobilized than when in solution. Immobilization stabilized the enzyme and made it less susceptible to activity loss during storage at pH values in the range 4–5.5, and the suicide inactivation of the immobilized tyrosinase was null or negligible in a reaction medium with 4‐tert‐butylcatechol at a concentration of 0.4 mmol dm^?3. The results show that cinnamic carbohydrate esters of D ‐sorbitol are an appropriate support for tyrosinase immobilization and could be of use for several tyrosinase applications. Copyright © 2005 Society of Chemical Industry     

A new method for the prediction of diffusion coefficients in poly(ethylene terephthalate)

Poly(ethylene terephthalate) (PET) is used in several packaging applications, especially for beverages. Due to the low concentration of potential chemical compounds like polymer additives or monomers leached out of the polymers and found in food or beverages, the compliance of a PET packaging material is shown often by use of migration modeling. Diffusion coefficients for migrants, however, are rare in the scientific literature. The aim of the study was to develop an equation for the prediction of diffusion coefficients in PET on the basis of activation energies of diffusion for possible migrants in PET. As a result, a correlation between experimentally determined activation energies of diffusion E_A and the volume of the migrant V was established for PET. In addition, a correlation of the pre‐exponential factor D₀ with the activation energy E_A was found. Combining both correlations lead to an equation where the diffusion coefficients D_P are predictable from the molecular volume V of the migrant. The equation might be useful for migration prediction and consumer exposure estimations. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

磁性聚丙烯酰胺-丙烯酸共聚纳米粒子固定脂肪酶的研究

用沉淀聚合制备了P(Am-co-Aa)-Gd(Ⅲ)磁性高分子纳米微球,在此基础上通过共价键合固定脂肪酶。结果表明:固定脂肪酶后的磁性纳米微球具有优异的磁分离能力;钆离子对固定化酶有明显的激活作用,当钆离子质量分数为0.8%时,偶联率和活力回收率分别提高57%和60%;脂肪酶被固定化后其pH稳定性,操作稳定性均比自由酶明显提高。     

五氯苯酚降解菌体固定化及降解动力学

五氯苯酚(PCP)是一种曾被广泛使用的木材防腐剂、杀菌剂和除草剂,目前已经造成了世界范围内土壤和水体的污染。本文针对筛选的4种优势菌株NERCDT-A、NERCDT-B、NERCDT-C、NERCDT-D,通过正交实验考察不同固定化材料、溶液pH值和生物接种量,确定出适宜的菌株固定化包埋条件。分别用游离单株优势菌和固定单株优势菌对PCP进行降解实验研究,对比结果表明固定化的菌株表现出了较好的降解效果。通过固定化菌株对PCP的降解动力学研究,确定不同固定化菌株的Monod参数。     

Poly(vinylbenzylchloride) beads grafted with polymer brushes carrying hydrazine ligand for reversible enzyme immobilization

Poly(glycidylmethacrylate), p(GMA), brush grafted poly(vinylbenzyl chloride/ethyleneglycol dimethacrylate), p(VBC/EGDMA), beads were prepared by suspension polymerization and the beads were grafted with poly(glycidyl methacrylate), p(GMA), via surface‐initiated atom transfer radical polymerization aiming to construct a material surface with fibrous polymer. The epoxy groups of the fibrous polymer were reacted with hydrazine (HDZ) to create affinity binding site on the support for adsorption of protein. The influence of pH, and initial invertase concentration on the immobilization capacity of the p(VBC/EGDMA‐g‐GMA)‐HDZ beads has been investigated. Maximum invertase immobilization onto hydrazine functionalized beads was found to be 86.7 mg/g at pH 4.0. The experimental equilibrium data obtained invertase adsorption onto p(VBC/EGDMA‐g‐GMA)‐HDZ affinity beads fitted well to the Langmuir isotherm model. It was shown that the relative activity of immobilized invertase was higher than that of the free enzyme over broader pH and temperature ranges. The K_m and V_max values of the immobilized invertase were larger than those of the free enzyme. After inactivation of enzyme, p(VBC/EGDMA‐g‐GMA)‐HDZ beads can be easily regenerated and reloaded with the enzyme for repeated use. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Reduction of Cr(VI) by palladized biomass of Desulfovibrio vulgaris NCIMB 8303

Palladized biomass of Desulfovibrio vulgaris (Bio‐Pd(0)) reduced Cr(VI) to Cr(III) at an initial rate four‐fold higher than chemically‐prepared Pd(0) metal. Optimal Cr(VI) reduction by suspended Bio‐Pd(0) occurred at pH 3, whereas pH did not affect the rate of Cr(VI) reduction by Bio‐Pd(0) immobilized in agar beads. The rate of Cr(VI) reduction was concentration‐dependent below 300 µmol dm^?3, and application of enzyme kinetics, considering Bio‐Pd(0) as an ‘artificial enzyme’, gave an apparent K_m (K_mapp) of approx. 650 µmol dm^?3 and V_max of 1667 nmol h^?1 mg Pd(0) for suspended Bio‐Pd(0). The potential of Bio‐Pd(0) as a method for the treatment of Cr(VI)‐wastes is discussed. Copyright © 2005 Society of Chemical Industry     

Surface immobilization of star‐shaped poly(ethylene oxide) on poly(dimethylsiloxane)

A thin layer of star‐shaped poly(ethylene oxide) (PEO) (starPEO), on the polydimethylsiloxane (PDMS) membrane was prepared by a simple immobilization procedure. Photoreactive molecules were introduced on the surface of the polymeric support to achieve the formation of thin starPEO film from the materials having no functional groups. This novel technique enabled us to immobilize any kind of chemical, especially one that had no functional groups, and readily to control the amount of immobilization. The gas permeation properties of the starPEO‐immobilized PDMS membranes were investigated for pure propane and propylene. The permeance of gases were found to decrease in the starPEO‐immobilized PDMS membranes, although the ideal separation factors for propylene/propane were increased with the loading amount of silver ions, because of the facilitation action of silver ions in the immobilized PEO unit on the PDMS membranes, as propylene carriers. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2369–2373, 2002     

Investigation of adsorption behaviors of Cu(II), Pb(II), and Cd(II) from water onto the high molecular weight poly (arylene ether sulfone) with pendant carboxyl groups

Three types of high molecular weight polyarylether adsorbents with different molar ratios of carboxyl and phenylene were designed and synthesized through direct polycondensation in mixture solvents. The as‐prepared polymers were characterized by FTIR, ¹H‐NMR, TGA, DSC, SEM, EDS, and GPC in order to study the regularity of polymeric adsorption/thermostability performances. Because of the highest molar ratio of carboxyl and phenylene, PAES‐C‐Na presented the highest adsorption capacity of Cu²⁺ compared to PAESK‐C‐Na and PAES; therefore, PAES‐C‐Na was opted to study the impacts of adsorbent dosage, pH, contact time, and initial concentration on the adsorption of Pb²⁺ and Cd²⁺. Moreover, a kinetic analysis revealed that the adsorption process followed pseudo‐second‐order model, while the thermodynamic experimental data properly fitted with the Freundlich model. The multi‐component competitive adsorption capacity followed the order Pb²⁺ > Cu²⁺ > Cd²⁺. Additionally, the regeneration tests indicated that PAES‐C‐Na still possessed the excellent adsorption capacity after several recycles. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41984.     

Comparative study of poly(vinyl alcohol)‐based support materials for the immobilization of glucose oxidase

BACKGROUND: The performances of four types of glucose oxidase (GOD) immobilization materials based on poly(vinyl alcohol) (PVA) were compared. The matrices of interest were chemically‐linked PVA, freeze‐thawed PVA cryogel, tetramethoxysilane (TMOS) sol‐gel‐PVA hybrid material, and alumina sol‐gel‐PVA hybrid material. RESULTS: Overall, the membranes showed good sensitivity except for the chemically cross‐linked PVA. However, the main differences with the enzyme immobilization methods were enzyme leakage and values of K_m^app. CONCLUSION: Freeze‐thawed PVA‐GOD membranes and TMOS‐PVA, which showed satisfactory sensitivity and adequate value of K_m^app, were quite promising as support materials for immobilizing GOD. Copyright © 2007 Society of Chemical Industry     

Covalent immobilization of antibodies for the preparation of immunoaffinity chromatographic supports

Immunosorbents in immunoaffinity chromatography (IAC) are prepared by immobilizing expensive antibodies without guidelines for ensuring the best coupling efficiencies, and avoiding low binding capacities. Covalent immobilization of antibodies on N-hydroxysuccinimide (NHS)-activated Sepharose 4 Fast Flow resin was optimized using human IgG via full factorial design with incubation times (4, 9, 14, 19 and 24 h), temperatures (4°C and 20°C) and coupling reaction buffers (sodium bicarbonate and triethanolamine). The best coupling efficiency (CE) (83.4 ± 8.7%) was reached with triethanolamine buffer, 14 h and 4°C. Comparison of antibody isotypes (IgG or IgM) by a nested factorial analysis suggested that antibodies in the IgG isotype presents the best coupling efficiency.