Clinoptilolite particles as a carrier for biocatalysts immobilization: invertase immobilization and characterization

Adsorption of soil invertase to goethite, gibbsite and their organic complexes and the effects on enzyme catalytic performance

Soil invertase plays important role in the enzyme-driven degradation of soil organic carbon, and influenced by the adsorption of minerals or clays. We studied the adsorption effects of goethite, gibbsite and their organic complexes (with tannic acid) on invertase, aiming to explore the influence on the mobility and catalytic behavior of invertase. Results showed that both minerals and mineral-tannic acid complexes (henceforth 'complexes') had considerable adsorption capacity for invertase and restricted its mobility. The catalytic performance of invertase was characterized. Under optimum conditions, the kinetics of the enzyme was reduced markedly after adsorption, indicating the decreased enzyme-substrate affinity. Adsorbed invertases retained 30.9-46.1% of the original activity and the mineral-adsorbed enzymes showed lower activities than the complex-adsorbed enzymes. All minerals and complexes had similar patterns on the influence on the pH and thermal properties of invertase, in which the adsorption improved the pH stability of the enzyme at various pH values, lowered the pH sensitivity and shifted the optimum pH towards the acid sites; while decreased thermal stability at various temperature values and higher temperature sensitivity of the adsorbed invertase were observed. In a 150-h incubation under soil-like conditions, all adsorbed invertases showed greater long-term stability than free invertase, and higher total activities (sum of adsorbed activities and dissolved activities) in adsorption system were observed after the incubation. These results implied that, in a soil microenvironment, the goethite, gibbsite and their organic complexes have a protection effect on invertase through adsorption.

The comparative study of a laccase-natural clinoptilolite-based catalyst activity and free laccase activity on model compounds

For the first time a laccase from Trametes versicolor was immobilized on a natural clinoptilolite with Si/Al=5 to obtain a biocatalyst for environmental applications. Immobilization procedures exploiting adsorption and covalent binding were both tested, and only the last provided enough activity for practical applications. The optimal conditions for the immobilization of the enzyme on the support and the kinetic parameters for the free and covalent bonded laccase were determined. The laccase bonded to the zeolitic support showed a lower activity than the free laccase, but the pH and thermal stability were greater. 20 mg of dry biocatalyst containing 1 U of laccase were able to remove in 50h 73-78% of 2-chlorophenol and 2,4-dichlorophenol in relatively concentrated aqueous solutions (100 μmol L(-1)).

Polyethyleneimine-grafted collagen fiber as a carrier for cell immobilization

Collagen fiber (CF), an abundant natural biopolymer, features many favorable properties that make it a potential carrier for cell immobilization. In the present investigation, CF was grafted with polyethyleneimine (PEI) using glutaraldehyde (GA) as the cross-linking agent, resulting in the formation of a novel CF based carrier (CF-PEI). The properties of CF-PEI as a carrier were evaluated by the immobilization of Microbacterium arborescens (CICC 20196), which has glucose isomerase (EC 5.3.1.5) activity. It was found that M. arborescens cells immobilized on CF-PEI exhibited higher glucose isomerization than those using activated carbon or anion exchange resin as the carriers. The Michaelis constant (K  m) of the isomerization reaction for the CF-PEI-immobilized M. arborescens cells was 0.528 mol/L, which was slightly higher than that of free cells (0.473 mol/L). In addition, the apparent activation energies (E  a) of free and immobilized cells on CF-PEI were almost the same at 60 kJ/mol. In an isomerization reaction of glucose to fructose in a fixed-bed reactor, CF-PEI-immobilized M. arborescens cells showed appreciable activity and operational stability. The corresponding isomerization ratio was as high as 41 % for 20 days, and the half-life was about 40 days.

A new method for the preparation of 1,3,5-triarylbenzenes catalyzed by nanoclinoptilolite/HDTMA

An efficient method for the preparation of 1,3,5-triarylbenzenes. Natural surface-modified NCP as a new and reusable catalyst. Using solvent-free conditions.