Biomimetic Mineralization Inducing Lipase–Metal–Organic Framework Nanocomposite for Pickering Interfacial Biocatalytic System

Abstract

In this study, a brand new biocatalytic system was successfully accomplished by combination of metal–organic frameworks (MOFs) biomimetic mineralization and Pickering interfacial system for enhanced lipase catalysis and recycling in organic media. Specifically, a highly porous lipase-loaded MOF composite was synthesized via biomimetic mineralization of ZIF-8 around lipase from Candida rugosa (CRL). With increasing enzyme loading amount, the role of CRL in modulating size, crystallinity, and interior or exterior structure of the composite was meticulously clarified. In this process, we disclosed a gradation from the crystal into an amorphous form for CRL-loaded ZIF-8 and more importantly discovered an enrichment of enzymes on the surface of the crystals. Combining this phenomenon with results of dynamic light scattering, zeta potential, and water contact angle, as well as styrene-induced interface solidification, we confirmed the surface-embedded CRL of the crystal played a role in adjusting the surface chemical characteristics of the composite that directly affected the stability of the emulsion and the distribution rule of stabilizers on the oil–water interface. Furthermore, through the comparison of hydrolyses involving a small substrate (p-nitrophenyl butyrate) and a larger one (p-nitrophenyl palmitate), a stable oil-in-water Pickering emulsion with an optimized quantity and integrity of oil droplets was proved to achieve the highest catalytic efficiency. Notably, because size selectivity of the ZIF-8 shell induced different locations of the substrates in contact with the enzymes, an obvious discrepancy in catalysis efficiency was observed for substrates with different sizes. Impressively, we could employ this system for transesterification by changing only the encapsulated enzyme (lipase B from Candida antarctica expressed in Aspergillus) and optimizing the oil/water ratio. The excellent catalytic performance highlighted the versatility of this interfacial biocatalytic system.

Hydrophobic pore space constituted in macroporous ZIF-8 for lipase immobilization greatly improving lipase catalytic performance in biodiesel preparation

“…The mean peak positions were α-helix (1656 cm −1 ), intramolecular β-sheet (1693 and 1633 cm −1 ), unordered and ordered helix (1672, 1648 and 1620 cm −1 ) and turn structures (1720, 1668, 1630 and 1617 cm −1 ). Notably, the peaks at 1627 cm −1 and 1622 cm −1 indicated the formation of intermolecular contacts [22]. According to Fig.…”

“…Since lipase is a kind of important enzyme applied in various fields especially in biodiesel production (lipase catalysis method), the immobilization of lipase on MOFs is worth studying for promoting its further application. Enzyme/MOF composites are typically synthesized through three approaches, including surface immobilization, pore adsorption (diffusion into the pores of MOFs), and encapsulation of enzymes within MOFs [20][21][22]. Nadar et al have activated the lipase in the presence of proline and successfully immobilized into zeolitic imidazolate framework (ZIF)-8 by biomineralization method.…”

Pickering Emulsion-Based Microreactors for Size-Selective Interfacial Enzymatic Catalysis

“…In this study, ZIF-8 and CalB@ZIF-8 nanoparticles were prepared via self-assembly and biomimetic mineralization methods as reported by us ( Scheme 1 ; Qi et al, 2019 ). The SEM images showed that both ZIF-8 and CalB@ZIF-8 nanoparticles presented rhombic dodecahedron, indicating that the encapsulation of the enzyme did not significantly affect the morphology of ZIF-8 nanoparticles.…”

“…However, it has been found that the introduction of enzymes in MOFs has certain impacts on the structural characteristics of MOF inevitably. Qi et al (2019) showed that the size of MOF nanoparticles loaded with lipase from Candida rugosa (CRL) was 2–3 times smaller than that of pure MOF nanoparticles. Therefore, recycling enzyme-MOF composites are hampered because the existing methods for separation, such as filtration and centrifugation, are obviously high time- and energy-consumption especially when the catalyst sizes are in the nanometer range.…”

Alcalase Microarray Base on Metal Ion Modified Hollow Mesoporous Silica Spheres as a Sustainable and Efficient Catalysis Platform for Proteolysis

“…cm −1 was assigned to β-sheet, random coil, α-helix, and βturn content, respectively (Qi et al, 2019). Furthermore, the contributions of each fraction of secondary structure were summarized in Table 3.…”