Influence of the Synthesis and Storage Conditions on the Activity of Candida antarctica Lipase B ZIF-8 Biocomposites

Abstract

The biomimetic mineralization of zeolitic imidazolate framework-8 (ZIF-8) has been reported as a strategy for enzyme immobilization, enabling the heterogenization and protection of biomacromolecules. Here, we report the preparation of different Candida antarctica lipase B biocomposites (CALB@ ZIF-8) formed by altering the concentrations of Zn 2+ and 2methylimidazole (2-mIM). The influence of synthetic conditions on the catalytic activity of the lipase CALB was examined by hydrolysis and transesterification assays in aqueous and organic media, respectively. We demonstrated that for both reactions, activity was retained for the biocomposites formed at low Zn 2+ /2-mIM ratios but notably almost entirely lost when the ligand concentration used to form the biocomposites was increased. Additionally, phosphate buffer could regenerate the activity of larger particles by degrading the crystal surfaces and releasing encapsulated CALB into solution. Transesterification reactions using CALB@ZIF-8 biocomposites were undertaken in 100% hexane, giving rise to enhanced CALB activity relative to the free enzyme. These observations highlight the fundamental importance of synthetic protocols and operating parameters for developing enzyme@ MOF biocomposites with improved activity in challenging conditions.

Sustainable One-Pot Immobilization of Enzymes in/on Metal-Organic Framework Materials

“…Thus, a fast crystallization process favors high catalytic activity retention [110] and leads to particles of smaller size. For example, in the lipase from Candida antarctica B immobilized in ZIF-8 (CaLB@ZIF-8), the small particles are afforded at low Zn:linker ratios and indeed keep higher catalytic activity [85]. Furthermore, the glucose oxidase (GOx) enzyme encapsulated in amorphous ZIF was 20 times more active than that encapsulated in crystalline ZIF-8 [78].…”

Confining enzymes in porous organic frameworks: from synthetic strategy and characterization to healthcare applications

“…Also, interestingly, the larger-sized biocomposites regained their bioactivity in phosphate buffer by decomposing the particle surfaces to release the CALB in solution. 213 As found by Ge's group, unlike most cases in which crystallized enzyme-ZIF-8 biocomposites were obtained, amorphous ZIF-8 (aZIF-8) was observed when the concentration of HmIM decreased (ratio of Zn 2+ to HmIM was 1 : 2 for the intact structure, while 1 : 1.69 for the amorphous structure) in the process of in situ encapsulating enzymes in ZIF-8. 216 In this assembling condition, the presence of coordination defects and mesopores was verified by molecular simulations and cryo-ET combined with other techniques.…”

“…In addition, the different assembling conditions through the alteration of the organic ligand/metal ion ratios may also decide the size and phase of the formed enzyme biohybrids, and further influence the entry of the substrate entrance and transport of the product. 67,199,[213][214][215][216] Doonan et al used different metal/ligand ratios to prepare CALB@ZIF-8 biocomposites with particle sizes ranging from 500 nm to 1 mm. 213 The catalytic activities of CALB@ZIF-8 for both hydrolysis and transesterification reactions were found to be closely related to its particle size (Fig.…”

“…67,199,[213][214][215][216] Doonan et al used different metal/ligand ratios to prepare CALB@ZIF-8 biocomposites with particle sizes ranging from 500 nm to 1 mm. 213 The catalytic activities of CALB@ZIF-8 for both hydrolysis and transesterification reactions were found to be closely related to its particle size (Fig. 22a).…”

App-based quantification of crystal phases and amorphous content in ZIF biocomposites

“…3 Once the ZIF biocomposite (biomacromolecule@ZIF) is formed, the encapsulated biomacromolecule can be protected against harsh environments 3,12 , can be stored without the need of refrigeration for long periods 5,9,12 and can be released in a controlled fashion by exposing the biocomposite to chelating agents (e.g. EDTA) 13 , acidic environments (e.g., pH≤6.5) 13,14 and buffer solutions (e.g., PBS) [13][14][15] . During the preparation of biomacromolecule@ZIF systems, reaction parameters (metal to ligand ratio, concentration, stirring or static conditions) and post-synthetic treatments (washing with water or ethanol) strongly influence the crystal structure of the Zn(mIM) 2 -based framework.…”