Chitin and chitosan: Properties and applications

Biological materials: Structure and mechanical properties

In this tutorial review, an overview of the why, what and how of enzyme immobilisation for use in biocatalysis is presented. The importance of biocatalysis in the context of green and sustainable chemicals manufacture is discussed and the necessity for immobilisation of enzymes as a key enabling technology for practical and commercial viability is emphasised. The underlying reasons for immobilisation are the need to improve the stability and recyclability of the biocatalyst compared to the free enzyme. The lower risk of product contamination with enzyme residues and low or no allergenicity are further advantages of immobilised enzymes. Methods for immobilisation are divided into three categories: adsorption on a carrier (support), encapsulation in a carrier, and cross-linking (carrier-free). General considerations regarding immobilisation, regardless of the method used, are immobilisation yield, immobilisation efficiency, activity recovery, enzyme loading (wt% in the biocatalyst) and the physical properties, e.g. particle size and density, hydrophobicity and mechanical robustness of the immobilisate, i.e. the immobilised enzyme as a whole (enzyme + support). The choice of immobilisate is also strongly dependent on the reactor configuration used, e.g. stirred tank, fixed bed, fluidised bed, and the mode of downstream processing. Emphasis is placed on relatively recent developments, such as the use of novel supports such as mesoporous silicas, hydrogels, and smart polymers, and cross-linked enzyme aggregates (CLEAs).

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Enzyme immobilisation in biocatalysis : Why, what and how

Application of chitosan, a natural aminopolysaccharide, for dye removal from aqueous solutions by adsorption processes using batch studies: A review of recent literature

Recent developments in polysaccharide-based materials used as adsorbents in wastewater treatment

Application of chitin- and chitosan-based materials for enzyme immobilizations: a review

Endowed with unparalleled high catalytic activity and selectivity, enzymes offer enormous potential as catalysts in practical applications. These applications, however, are seriously hampered by enzymes’ low thermal and chemical stabilities. One way to improve these stabilities is the enzyme immobilization. Among various tested methods of this process that make use of different enzyme-carrier interactions, immobilization by adsorption on solid carriers has appeared most common. According to these findings, in this review we present a comparative analysis of the literature reports on the recent trends in the immobilization of the enzymes by adsorption. This thorough study was prepared in order to provide a deeper understanding of the process. Both carriers, carrier modifiers and procedures developed for effective adsorption of the enzymes are discussed. The review may thus be helpful in choosing the right adsorption scheme for a given enzyme to achieve the improvement of its stability and activity for a specific application.

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Enzyme immobilization by adsorption: a review

Ureases (urea amidohydrolases, EC 3.5.1.5) are a group of highly proficient enzymes, widely distributed in nature, whose catalytic function is to catalyze the hydrolysis of urea, its final products being carbonic acid and ammonia. The products and the resulting increase in pH of the reaction environment are consequential characteristics of the action of ureases. Apart from its natural significance, ureases-catalyzed hydrolysis of urea is important in that it has great potential for practical applications. In view of this importance, this article offers a review of the properties of the enzymes, where in addition to the established knowledge, the recent findings are presented. Special emphasis is put on the functional and practical properties of ureases that can be customized and exploited in a diversity of important applications, notably medical, analytical, environmental and engineering.

Barbara Krajewska

Papers

Application of chitin- and chitosan-based materials for enzyme immobilizations: a review

Enzyme immobilization by adsorption: a review

Ureases I. Functional, catalytic and kinetic properties: A review

Membrane-based processes performed with use of chitin/chitosan materials

Chitosan as a lipid binder: a langmuir monolayer study of chitosan-lipid interactions.