Preparation of polymeric macroporous hydrogels for the immobilization of enzymes using an emulsion-gelation method

Novel polymeric macroporous hydrogels were developed to entrap and immobilize lipase. Poly(ethylene glycol) methyl ether acrylate hydrogel was used as the support. The emulsion-gelation method using oil-in-water emulsions was used to simultaneously synthesize the hydrogels and entrap lipase in the randomly distributed, non-interconnected, sphere-like macropores, which were several micrometers in diameter. The lipase, immobilized within the macroporous hydrogel, successfully catalyzed the hydrolysis of triacetin without leakage of lipase or loss of activity during repeated use. The macroporous hydrogel-immobilized lipase exhibited higher activity than the lipase immobilized within a non-porous hydrogel, which indicates entrapment of lipase in the macropores without interference from the polymer and excellent diffusional permeability of macroporous hydrogel to substrate/product species.     

Recent advances in polymeric membranes for CO2 capture

Membrane and membrane process have been considered as one of the most promising technologies for mitigating CO₂ emissions from the use of fossil fuels. In this paper, recent advances in polymeric membranes for CO₂ capture are reviewed in terms of material design and membrane formation. The selected polymeric materials are grouped based on their gas transport mechanisms, i.e., solution‐diffusion and facilitated transport. The discussion of solution‐diffusion membranes encompasses the recent efforts to shift the upper bound barrier, including the enhanced CO₂ solubility in several rubbery polymers and novel methods to construct shape-persisting macromolecules with unprecedented sieving ability. The carrier-bearing facilitated transport membranes are categorized based on the specific CO₂-carrier chemistry. Finally, opportunities and challenges in practical applications are also discussed, including post-combustion carbon capture (CO₂/N₂), hydrogen purification (CO₂/H₂), and natural gas sweetening (CO₂/CH₄).     

Plasma treatment of polymeric fibers for improved performance in cement matrices

The surfaces of collated fibrillated polypropylene fibers and monofilament polyolefin fibers were treated by low‐temperature cascade arc plasma with different gases to study the effect of interface treatment on the mechanical performance and toughening in fiber‐reinforced concrete composites. Results from static flexural tests conducted in a four‐point configuration on 17 concrete mixes including one unreinforced control mix, 4 mixes with untreated fibers (two volume contents for each of two fiber types—fibrillated and monofilament), and 12 mixes with plasma‐treated fibers (two volume contents, above two fiber types, and three plasma treatments) are presented and discussed. It is concluded that plasma treatment of polymeric fibers is effective in improving the flexural performance and toughness of fiber reinforced concrete composites. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1985–1996, 2000     

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).     

Immobilization of horseradish peroxidase in three-dimensional macroporous TiO2 matrices for biosensor applications

Three-dimensional macroporous TiO₂ was synthesized by a sol-gel procedure using polystyrene colloidal crystals as templates. SEM showed that a face-centered cubic (FCC) 3D macroporous structure was obtained. Horseradish peroxidase (HRP) was successfully immobilized on the surface of an optically transparent electrode (OTE). Photoelectrochemical properties were characterized using a three electrodes system and an ultraviolet lamp. The HRP/TiO₂/OTE displays a rapid photocurrent response, approximately 178.7 nA, under UV illumination (380 nm). The sensitivity of H₂O₂ detection was 70.04 μA/mM without UV illumination, and it increased to 102.97 μA/mM when illuminated by UV. The amperometric response was also enhanced. The high response was due to the good biocompatibility of TiO₂ and excellent photoelectrical property and the large effective surface of the three-dimensionally ordered macroporous structure.     

Dye derived and metal incorporated affinity poly(2-hydroxyethyl methacrylate) membranes for use in enzyme immobilization

Microporous poly(2-hydroxyethyl methacrylate) (PHEMA) membranes were prepared by UV-initiated photopolymerization of HEMA in the presence of an initiator (α,α′-azobisisobutyronitrile, AIBN). An affinity dye Cibacron Blue F3GA (CB) was attached covalently and then Fe³⁺ ions incorporated. The PHEMA-CB and PHEMA-CB-Fe³⁺ membranes derived were used for adsorption of glucose oxidase (GOD). The adsorption capacities of these membranes were determined under conditions of different pH and with different concentrations of the adsorbate in the medium. The adsorption phenomena appeared to follow a typical Langmuir isotherm. The glucose oxidase adsorption capacity of the Fe³⁺ incorporated membrane (87μgcm^-2) was greater than that of the dye-derived membrane (66μgcm^-2). Non-specific adsorption of the glucose oxidase on the PHEMA membranes was negligible. The K_m values for both immobilized glucose oxidase PHEMA-CB-GOD (8·3) and PHEMA-CB-Fe³⁺-GOD (7·6) were higher than that of the free enzyme (6·2mM). Optimum reaction pH was 5·5 for the free and 6·0 for both immobilized preparations. The optimum reaction temperature of the adsorbed enzymes was 5°C higher than that of the free enzyme and was significantly broader. After 15 successive uses the retained activity of the adsorbed enzyme was 87%. It was observed that enzymes could be repeatedly adsorbed and desorbed on the derived PHEMA membranes without significant loss in adsorption capacity or enzymic activity. © 1998 SCI.