-D-glucosidase chemically bound to microcrystalline cellulose

Cellulose carbonates: a platform for promising biopolymer derivatives with multifunctional capabilities

Cellulose carbonates as a platform compound open new possibilities for the design of advanced materials based on the most important renewable resource cellulose. In the present feature, the chemistry of cellulose carbonates is discussed considering own research results adequately. After a short overview about methods for activation of polysaccharides for a conversion with nucleophilic compounds in particular with amines, details about various methods for the synthesis of polysaccharide carbonates are discussed. The main issue of the feature is the synthesis and aminolysis of cellulose carbonates with low, intermediate, and high degree of substitution and the evaluation of this chemistry with respect to specific challenges. Functional cellulose carbamates, obtained from cellulose phenyl carbonate by aminolysis, show the potential use of this class of celluloses. Immunoassays and zwitterionic polymers are included as representative examples regarding properties and application of the new cellulose-based products.

Immobilization of Aspergillus beta-glucosidase on chitosan

beta-Glucosidase of Aspergillus phoenicis QM 329 was immobilized on chitosan, using the bifunctional agent glutaraldehyde. The most active preparation based on the amount of support contained a 1:2.5 enzyme-to-chitosan ratio (wt/wt). However, the specific activity of the bound enzyme decreased from 10 to 1% with increasing enzyme-to-chitosan ratio. Compared with free beta-glucosidase, the immobilized enzyme exhibited: (i) a similar pH optimum but more activity at lower pH values; (ii) improved thermal stability; (iii) a similar response to inhibition by glucose; and (iv) mass transfer limitations as reflected by higher apparent Km and lower energy of activation.

Magnetic, immobilised derivatives of enzymes

A novel, water, insoluble, stable coating has been attached to various metals, which is capable of covalent attachment to enzymes. The coating (aminobenzoic acid-formaldehyde resin) can be attached to nickel, cobalt, tin, iron, and aluminium. beta-D-Glucosidase has been attached to the coated metals by diazotisation of the coating. The stability and usefulness of the resulting, metallic enzyme-preparations is discussed with special emphasis on the value of ferromagnetic supports for enzymes.

The use of cellulose xanthate for the immobilisation of biological molecules

The mercapto groups of cellulose xanthate can reversibly form disulphide bridges with L-cysteine. This property has been utilised for the immobilisation of a protein and an enzyme. These macromolecules, as polythiol derivatives, formed disulphide linkages with the matrix without serious disturbance of their active sites, became firmly bound to the xanthate, and were not eluted by normal washing conditions. Cellulose xanthate is a cheap, easily prepared matrix which permits a simple coupling reaction. The immobilisation process is selectively reversible.

Active insolubilized antibiotics based on cellulose and cellulose carbonate

The coupling of a number of antibiotics to cellulose and cellulose trans-2,3-carbonate under a series of coupling conditions has been investigated, and it has been shown that by such couplings active insoluble derivatives of antibiotics can be produced. It was found that the antibiotics became firmly bound to cellulose itself, whereas use of cellulose carbonate extended the range of antibacterial activity retained. In the case of cellulose, it was considered that physical adsorption phenomena were operating, whereas a covalent bond was more likely in the case of cellulose carbonate where the antibiotic amino groups could attack the electrophilic cyclic carbonate carbon atoms. The release of antibiotic from the matrix during testing of antibacterial activity was likely due to the action of a cellulase or additionally an esterase in the case of cellulose carbonate. The importance and potential of these new types of chemical derivatives are discussed in terms of new outlets for the commerical use of cellulose.