Laccase Encapsulation in ZIF‐8 Metal‐Organic Framework Shows Stability Enhancement and Substrate Selectivity

Abstract

CgL1 laccase from Corynebacterium glutamicum was encapsulated into the metal‐organic framework (MOF) ZIF‐8 which was synthesized in a rapid enzyme friendly aqueous synthesis, the fastest in situ encapsulation of laccases reported to date. The obtained enzyme/MOF, i. e. laccase@ZIF‐8 composite showed enhanced thermal (up to 70 °C) and chemical (N,N‐dimethylformamide) stability, resulting in a stable heterogenous catalyst, suitable for high temperature reactions in organic solvents. Furthermore, the defined structure of ZIF‐8 produced a size selective substrate specificity, so that substrates larger than the pore size were not accepted. Thereby, 2’‐azino‐bis(3‐ethylbenzothiazoline‐6‐sulphonic acid) (ABTS) was used to verify that the enzyme is immobilized inside the MOF versus the outside surface. The enzyme@MOF composite was analyzed by atomic absorption spectroscopy (ASS) to precisely determine the enzyme loading to 2.1 wt%.

A Systematic Study of the Stability of Enzyme/Zeolitic Imidazolate Framework‐8 Composites in Various Biologically Relevant Solutions

“…SEM showed that GOx@ZIF‐8 was smaller than ALP@ZIF‐8 in particle size. The shape of these composites was similar to those reported in some studies [15,18,24] but different from the polyhedral shape reported in others [5,7,8] . The variations in morphology ( e. g .…”

“…It is therefore likely that the susceptibility of enzyme@ZIF‐8 composites to these chemical agents is not greatly affected by the exact nature of the proteins in the composites. However, the morphology, particle size and crystallinity of the enzyme@ZIF‐8 composites do appear to vary among studies even under similar synthesis conditions [5,7,8,15,18,24] and surface area of lipase@ZIF‐8 is affected by the Zn 2+ /2‐MI molar ratio during synthesis [61] . It is likely that these properties ( i. e .…”

“…The conditions used in the synthesis (i. e. in aqueous solution, at mild pH and ambient temperature and for short periods of time) are also compatible with enzymes. A wide range of enzymes have been encapsulated in ZIF-8, including cytochrome c, [5][6][7] horseradish peroxidase, [5,6,[8][9][10] lipase, [5,6,[11][12][13] glucose oxidase (GOx), [9,14] laccase, [12,15,16] catalase, [17] urease, [18] glucoamylase, [19] chloroperoxidase [20] and phenylethanol dehydrogenase. [21] It is also possible to encapsulate multiple enzymes in the same ZIF-8 for cascade reactions.…”

“…[22] Encapsulation of enzymes in ZIF-8 provides several advantages. Compared with their free counterparts, the encapsulated enzymes generally display higher stability under harsh conditions, including at elevated temperatures, [6,8,15,16,[18][19][20] in the presence of organic solvents, [6,9,15,20] or at extreme pH. [17] The encapsulation also shields the enzymes from protease digestions.…”

Study on improving the stability of adsorption-encapsulation immobilized Laccase@ZIF-67

“…There are hundreds of existing ZIFs [ 26 ], ZIF-8 (Zn(mIm) 2 , mIm = 2-methylimidazolate), which is the most common and widely investigated ZIFs [ 27 ]. The method to synthesize laccase@ZIF-8 composite has been reported in some literature [ [28] , [29] , [30] , [31] ]. ZIF-67 (Co(mIm) 2 , mIm = 2-methylimidazolate), which is also the most representative ZIF materials with a zeolite sod topology [ 32 ].…”