Abstract
Cyclodextrins (CDs) and their derivatives have attracted significant attention in the pharmaceutical, food, and textile industries, which has led to an increased demand for their production. CD is typically produced by the action of cyclodextrin glycosyltransferase (CGTase) on starch. Owing to the relatively high cost of enzymes, the economic feasibility of the entire process strongly depends on the effective retention and recycling of CGTase in the reaction system, while maintaining its stability. CGTase enzymes immobilized on various supports such as porous glass beads or glyoxyl-agarose have been previously used to achieve this objective. Nevertheless, the attachment of biocatalysts on conventional supports is associated with numerous drawbacks, including enzyme leaching prominent in physical adsorption, reduced activity as a result of chemisorption, and increased mass transfer limitations. Recent reports on the successful utilization of metal–organic frameworks (MOFs) as supports for various enzymes suggest that CGTase could be immobilized for enhanced production of CDs. The three-dimensional microenvironment of MOFs could maintain the stability of CGTase while posing minimal diffusional limitations. Moreover, the presence of different functional groups on the surfaces of MOFs could provide multiple points for attachment of CGTase, thereby reducing enzyme loss through leaching. The present review focuses on the advantages MOFs can offer as support for CGTase immobilization as well as their potential for application in CD production.
Highlights
Cyclodextrins (CDs) are valuable compounds which have found applications in numerous fields, including the pharmaceutical, medical, food, and cosmetic industries
From the supports used in the literature for cyclodextrin glycosyltransferase (CGTase) immobilization, it is evident that apart from differences in physical characteristics such as the pore diameter, particle size, and mechanical strength, the performance of the CGTase/support depends on the type and density of the functional group used, the length of the coupling agent, and the pore network of the support
Covalent attachment was identified as the best immobilization technique for CGTase, with density of the functional group, length of the coupling agent, and type of pores present in the support affecting the reusability of the matrix and diffusion of both reactant and product when used in CD production
Summary
Cyclodextrins (CDs) are valuable compounds which have found applications in numerous fields, including the pharmaceutical, medical, food, and cosmetic industries. Chemical adsorption provides a stronger attachment to the support and, results in resistance to leaching, the chemical bonds formed between the enzyme and support affect the activity of the biocatalyst. Other immobilization matrices such as sol-gel, hydrogels, and mesoporous silica have recently been suggested to overcome the leaching problem without affecting enzyme activity [5,6,7,8]. The above materials exhibit low immobilization efficiency and high mass transfer They cannot be used for bulky substrates due to the restricted access to the pores [5,6]. The critical discussion presented in the review paves the way for researchers to investigate the effectiveness of using MOFs in this very important application
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