Search

Lipase is an industrial enzyme, the catalytic efficiency of which is restricted by various environmental factors. To improve this efficiency, immobilization technology has been utilized in the past to improve the stability of lipase in harsh conditions. Immobilization technology can be divided into physical methods and chemical methods. Some unsolved problems remain in current immobilization technology. The interaction between enzyme and immobilization support is weak and reversible during physical adsorption, resulting in poor stability of the immobilized enzyme and the contamination of substrate solution by leached enzymes. In chemical methods, enzyme-active sites might be inactivated due to the chemical reactions between enzyme molecules and support, resulting in a decrease in the enzymes' catalytic activity (Liu et al., 2018a). The objective of the current study was to construct a nanostructured lipase via Mg-amino-clay as a carrier and improve the catalytic activity and stability of lipase by immobilization. Lipase produced by Aspergillus oryzae was immobilized on aminopropyl functionalized magnesium phyllosilicate (a 2:1 trioctahedral talc-like silicate Mg-amino-clay) via a 1-(3-Dimethylaminopropyl)-3-ethyl-carbodiimide hydrochloride (EDC) coupling agent. The physical and chemical properties of the Mg-amino-clay and Mg-amino-clay-based nanostructured biocatalyst (Mg-clay-lipase) were characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, and scanning electron microscopy. Optimal immobilization conditions were determined by taking into account the following variables: amount of initial lipase, EDC concentration, and reaction time. The results revealed that the optimum temperature, pH, and thermal stability of Mg-clay-lipase were greater than equivalent values for free lipase under optimal conditions (described below – Process for Immobilization of Lipase on Mg-amino-clay). The Michaelis-Menten constant (Km) values were 5.25 mM and 7.42 mM while the maximum reaction rates (vmax) were 30.58 mM/(L·min) and 55.87 mM/(L·min) for free lipase and Mg-clay-lipase, respectively. The present study provided a new nanostructured biocatalyst and demonstrated that the enzyme activity and stability of Mg-clay-lipase were superior to those of free lipase due to the mechanism of 'interface activation'. [ABSTRACT FROM AUTHOR]

Encapsulation of two enzymes, alcohol dehydrogenase (ADH) and glucose oxidase (GOx), within peroxidase-like tourmaline microparticle (TM)-based colloidosomes was used to construct a functionalized microsystem capable of sustainable cascade cycling of nicotinamide cofactor (NAD+/NADH) via chemical signaling between spatially confined dual-enzyme and active membranes. [ABSTRACT FROM AUTHOR]

The bioinspired design and construction of enzyme@capsule microreactors with specific cell-like functionality has generated tremendous interest in recent years. Inspired by their fascinating complexity, scientists have endeavored to understand the essential aspects of a natural cell and create biomimicking microreactors so as to immobilize enzymes within the hierarchical structure of a microcapsule. In this study, simultaneous encapsulation of alcohol dehydrogenase (ADH) was achieved during the preparation of microcapsules by the Pickering emulsion method using amphiphilic modified TiO2 nanoparticles (NPs) as building blocks for assembling the photocatalytic microcapsule membrane. The ADH@TiO2 NP microreactors exhibited dual catalytic functions, i.e., spatially confined enzymatic catalysis and the membrane-associated photocatalytic oxidation under visible light. The sustainable cycling of nicotinamide adenine dinucleotide (NAD) coenzyme between NADH and NAD+ was realized by enzymatic regeneration of NADH from NAD+ reduction, and was provided in a form that enabled further photocatalytic oxidation to NAD+ under visible light. This bioinspired ADH@TiO2 NP microreactor allowed the linking of a semiconductor mineral-based inorganic photosystem to enzymatic reactions. This is a first step toward the realization of sustainable biological cycling of NAD+/NADH coenzyme in synthetic functional microsystems operating under visible light irradiation. [ABSTRACT FROM AUTHOR]

Clay minerals provide an excellent platform for enzyme immobilization, which can improve enzyme activity and stability for industrial applications. In this study, lipase from Aspergillus oryzae was immobilized on 3-aminopropyltriethoxysilane (APTES) amphiphilic functionalized montmorillonite (Mt) support via 1-(3-Dimethylaminopropyl)-3-ethyl-carbodiimide hydrochloride (EDC) spacer. The APTES-Mt and APTES-Mt based nanostructured biocatalyst (lipase-Mt) were characterized by XRD, FT-IR, TEM, SEM and contact angle analysis. Optimal immobilization conditions were determined considering parameters of EDC concentration, initial lipase concentration, pH, and reaction time. The results indicated that lipase-Mt activity was 40.65 U/mg, which was nearly 4-fold higher than that of free lipase under optimal conditions. The Michaelis-Menten constant (K m) were found as 0.357 mM and 3.406 mM for free and lipase-Mt, respectively. The maximum reaction rate (V max) for the free and lipase-Mt were calculated as 63.69 mM/(L·min) and 312.5 mM/(L·min), respectively. Further, the interfacial activation by amphiphilic surface of APTES-Mt and enlarged catalytic interface contributed to the improved activity and storage stability of lipase-Mt. Thus, this work demonstrate an economically viable method for constructing nanostructured biocatalyst for industrial applications based on covalent immobilization of enzyme onto clay minerals. Unlabelled Image • Lipase was immobilized on aminopropyl-functionalized montmorillonite support. • Optimal immobilization conditions were determined considering different parameters. • The catalytic activities of immobilized lipase is higher than that of free lipase. • Immobilized lipase have better operation and storage stability. [ABSTRACT FROM AUTHOR]