Immobilization in Layered Double Hydroxides

Layered double hydroxides (LDH), also referred to as anionic clays, are very useful materials due to their anion exchange properties. LDH display a layered structure built on a stacking of positive layers ([MII1 MIII (OH)2] +), separated by inter-lamellar domains constituted of anions and water molecules ([X e nH20]x ) [117]. 

A second process of enzyme entrapment in LDH was also performed using colloidal solutions of LD H. Such colloidal solutions can be prepared by delamination 

Calcined [MgAl] LDH was also used to adsorb penicillin G acylase [121]. The calcined LDH phases have porous structures, large specific surface areas and abundant basic sites to bind the enzymes. The effect of varying the composition of the LDH precursor and calcination temperature on the activity of the immobilized enzyme has been reported. In this case, the percentage of immobilized proteins increases up to 88 %. 

A more sophisticated method was developed by Ren et al. [123] for the immobilization of penicillin G acylase by covalent grafting in the interlayer galleries of a LDH by a three-step procedure using a glutamate pillared LDH as the starting material. 

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