Crosslinked Chitosan Membrane Research Articles

Enzyme immobilization in novel alginate–chitosan core-shell microcapsules

Alginate–chitosan core-shell microcapsules were prepared in order to develop a biocompatible matrix for enzyme immobilization, where the protein is retained either in a liquid or solid core and the shell allows permeability control over substrates and products. The permeability coefficients of different molecular weight compounds (vitamin B2, vitamin B12, and myoglobin) were determined through sodium tripolyphosphate (Na-TPP)-crosslinked chitosan membrane. The microcapsule core was formed by crosslinking sodium alginate with either calcium or barium ions. The crosslinked alginate core was uniformly coated with a chitosan layer and crosslinked with Na-TPP. In the case of calcium alginate, the phosphate ions of Na-TPP were able to extract the calcium ions from alginate and liquefy the core. A model enzyme, β-galactosidase, was immobilized in the alginate core and the catalytic activity was measured with o-nitrophenyl- β- d-galactopyranoside (ONPG). Change in the activity of free and immobilized enzyme was determined at three different temperatures. Na-TPP crosslinked chitosan membranes were found to be permeable to solutes of up to 17,000 Da molecular weight. The enzyme loading efficiency was higher in the barium alginate core (100%) as compared to the calcium alginate core (60%). The rate of ONPG conversion to o-nitrophenol was faster in the case of calcium alginate–chitosan microcapsules as compared to barium alginate–chitosan microcapsules. Barium alginate–chitosan microcapsules, however, did improve the stability of the enzyme at 37°C relative to calcium alginate–chitosan microcapsules or free enzyme. This study illustrates a new method of enzyme immobilization for biotechnology applications using liquid or solid core and shell microcapsule technology.

Transport Phenomena of Chitosan Membrane in Pervaporation of Water-Ethanol Mixture

ABSTRACT The pervaporation transport process of H2O-EtOH solution was studied on a chitosan membrane and on a H2SO4 crosslinked chitosan membrane. The influence of concentration, temperature, and crosslinking was also studied. The dependence of permeation fluxes on feed concentration showed strong coupling effects existed in the permeation process. That the thermodynamic swelling—distribution relationship changed with the feed concentration also showed that a strong coupling effect existed in the thermodynamic swelling process. The permeation fluxes and thermodynamic swelling processes showed analogous relationships versus the concentration in the feed. The high swelling ratio and the high selectivity of the membrane in the thermodynamic swelling distribution process was the basis ofhigh flux and high permselectivity of pervaporation. With an increase of temperature, the permeation fluxes increased quickly, but the swelling ratio of water and EtOH in the membrane scarcely changed. This showed that an increase of temperature promoted the diffusion process but had little influence on permselectivity. The permselectivity of pervaporation depended strongly on the thermodynamic swelling process.

Separation of Water/Ethanol Vapor Mixtures through Chitosan and Crosslinked Chitosan Membranes

Abstract The separation of water/ethanol vapor mixtures through chitosan membranes and crosslinked chitosan membranes was studied by means of the vapor permeation technique. The permeation performance was discussed in terms of separation factor and permeation flux. Crosslinking the chitosan membrane by glutaraldehyde enhanced the selectivity. The highest separation factor obtained was 6000 for a crosslinked chitosan membrane with a degree of deacetylation of 100%.

Structure of chemically modified chitosan membranes and their characteristics of permeation and separation of aqueous ethanol solutions

The structure of chitosan membranes chemically modified with aldehydes, such as glutaraldehyde and n-butyl aldehyde, was analyzed. Characteristics of permeation and separation of aqueous ethanol solutions through the membranes were investigated by evapomeation. Chitosan membranes reacted with glutaraldehyde were cross-linked by Schiff base bonds and had no pendant structure. Density and crystallinity of the cross-linked chitosan membranes decreased with increasing glutaraldehyde content in the membranes. The permeation rate, separation factor for water permselectivity, and degree of swelling of the cross-linked chitosan membrane for aqueous ethanol solutions increased with increasing glutaraldehyde content in the chitosan membrane. The structure of the chemically modified chitosan membrane and the permeation and separation characteristics for aqueous ethanol solutions are discussed from the viewpoint of hydrogen bonds of the cross-linked membrane.

Dehydration of aqueous pyridine solution through crosslinked chitosan membrane

The present study investigates the pervaporation performance of crosslinked chitosan membrane for the dehydration of aqueous pyridine solution. The control of the degree of crosslinking contributes to an improved pervaporation performance of chitosan membranes. The chitosan membrane crosslinked with 4.515x15-4 (mol/g polymer) glutaraldehyde solution shows the separation factor of 510 and the flux of 140g/m2hr measured with 93wt% aqueous pyridine solution at 25°C.

Permeation and separation characteristics of ethanol-water mixtures through chitosan derivative membranes by pervaporation and evapomeation

This paper deals with permeation and separation characteristics of aqueous ethanol solutions through some chitosan derivative membranes such as chitosan, chitosan acetate and crosslinked chitosan membranes by pervaporation and evapomeation methods. The evapomeation method was found to be better than the pervaporation method for the permeation and separation of aqueous ethanol solutions. Separation factors for aqueous ethanol solutions containing more than 90 wt% of ethanol through a chitosan acetate membrane were about ten times that through a chitosan membrane. Also, the separation factor of a chitosan membrane crosslinked with glutaraldehyde was infinity for a feed of less than 70 wt% of ethanol and was about 20 times the chitosan membrane at 90 wt% of ethanol. Permeation rates of the crosslinked chitosan membrane were greater than those of the chitosan membrane. The permeation and separation characteristics for aqueous ethanol solutions are discussed from the viewpoints of the structure of chitosan derivative membranes and the permeation mechanism through the membrane.

Studies on Syntheses and Permeabilities of Special Polymer Membranes. 59. Active Transport of Organic Ions through Crosslinked Chitosan Membrane

Abstract Active transport of organic ions such as benzenesulfonate and benzoate ions and amino acids was studied through a chitosan–PVA membrane under various conditions. The organic anions of benzenesulfonate and benzoate ions were actively transported through the chitosan–PVA membrane from the acidic side to the alkaline side, but the active transport of amino acid occurred from the alkaline side to the acidic side. These active transports were significantly dependent on a pH difference and electric potential difference between the two sides of the membrane