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Effective preservation of enzyme activity is required for using immobilized enzymes to catalyze reactions. To this end, the co-immobilization of an enzyme and nanoparticles in a nanosphere system using a reverse microemulsion is proposed. Iron oxide nanoparticles (MNPs) and carboxyl esterase (CE) were encapsulated in spherical mesoporous silica nanospheres. After immobilization, the encapsulated CE retained approximately 10.9% of the specific activity of free CE for the hydrolysis reaction. Regarding its stability during storage, the immobilized CE retained 52% and 30% of its initial activity after 30 days at 25 °C and under rigorous incubation conditions, respectively. Utilizing this magnetically separable property enabled the immobilized CE to be recycled 13 times through easy magnetic separation. The encapsulation of CE in silica nanospheres improved the efficiency of the enzymatic reactions by reducing the mass transfer limitation without any structural changes upon immobilization. This is the first demonstration of the co-encapsulation of MNPs and enzymes in mesoporous silica nanospheres to form stabilized and immobilized enzyme systems for biocatalytic applications. • Co-immobilization of CE and MNPs into mesoporous silica nanospheres was assembled. • They preserved 13 reuse cycles with 30 days of storage, with magnetic separability. • Efficient demonstration of a nanobiocatalyst, resulting in a stabilized enzyme. [ABSTRACT FROM AUTHOR]

Immobilization is a key technology for successful realization of enzyme-based industrial processes, particularly for production of green and sustainable energy or chemicals from biomass-derived catalytic conversion. Different methods to immobilize enzymes are critically reviewed. In principle, enzymes are immobilized via three major routes (i) binding to a support, (ii) encapsulation or entrapment, or (iii) cross-linking (carrier free). As a result, immobilizing enzymes on certain supports can enhance storage and operational stability. In addition, recent breakthroughs in nano and hybrid technology have made various materials more affordable hosts for enzyme immobilization. This review discusses different approaches to improve enzyme stability in various materials such as nanoparticles, nanofibers, mesoporous materials, sol-gel silica, and alginate-based microspheres. The advantages of stabilized enzyme systems are from its simple separation and ease recovery for reuse, while maintaining activity and selectivity. This review also considers the latest studies conducted on different enzymes immobilized on various support materials with immense potential for biosensor, antibiotic production, food industry, biodiesel production, and bioremediation, because stabilized enzyme systems are expected to be environmental friendly, inexpensive, and easy to use for enzyme-based industrial applications. [ABSTRACT FROM AUTHOR]

Lipases catalyze a wide range of industrially important reactions, including the transesterification of triglycerides with alcohols for biodiesel production, and the stabilization of lipases are critical to achieve their recycled uses. Here, nanoscale enzyme reactor (NER) of lipase from Rhizopus oryzae (LP) was prepared via a simple two-step process, comprising of enzyme adsorption into magnetically-separable mesoporous silica and follow-up crosslinking of adsorbed enzymes. In aqueous phase, the specific hydrolysis activity of NER-LP was 4.7 times lower than that of free LP. On the other hand, however, the specific transesterification activity of NER-LP (130.4 μmol/min/mg LP) in organic phase for biodiesel production was 50 times higher than that of free LP (2.6 μmol/min/mg LP). These results reveal that the enzyme crosslinking for the preparation of NER does not interfere with the interfacial activation of LP molecules, opening the lid of LP active site under an optimal hydrophobic environment provided by the combination of organic solvent and mesoporous silica. Magnetic separation and optimized washing protocol facilitated the recycled uses of NER-LP. Highly stable and active NER-LP in magnetically-separable mesoporous silica has demonstrated its great potentials as an environmentally-friendly nanobiocatalyst for various lipase applications, including plasticizers, biosurfactants, functional fatty acids, as well as recyclable biodiesel production. • Lipase (LP) is immobilized in mesoporous silica via nanoscale enzyme reactor (NER) stabilizes the activity of LP. • Specific transesterification activity of NER for biodiesel production is increased by the interfacial activation of LP. • Recycled use of NER is optimized by effective washings via magnetic separation. [ABSTRACT FROM AUTHOR]

Enzyme immobilization using inorganic materials has been shown to preserve enzyme activity improving and improve their practical applications in biocatalytic process designs. Proper immobilization methods have been used to obtain high recycling and storage stability. In this study, we compared the activity and stability of in situ or crosslink-immobilized enzymes in a CaCO 3 biomineral carrier. More than 30% of the initial enzyme activity was preserved for both the systems after 180 days upon 15 activity measurements at room temperature, confirming the improved stability of these enzyme systems (100 mM phosphate buffer, pH 8.0); however, differences in enzyme loading, activity, and characteristics were observed for each of these methods. Each system exhibited efficacy of 80% and 20%, respectively. Based on the same amount of immobilized enzyme (0.2 mg), the specific activities of hydrolysis of p -nitrophenyl butyrate substrate at room temperature of in situ immobilized carboxyl esterase (CE) and crosslinked CE were 11.37 and 7.63 mM min−1 mg−1, respectively (100 mM phosphate buffer, pH 8.0). Moreover, based on the kinetic behavior, in situ immobilized CE exhibited improved catalytic efficiency (Vmax Km−1) of the enzyme, exhibiting 4-fold higher activity and efficiency values than those of the CE immobilized in CaCO 3. This is the first study to describe the stabilization of enzymes in CaCO 3 and compare the enzyme kinetics and efficiencies between in situ immobilization and crosslinking in CaCO 3 carriers. [ABSTRACT FROM AUTHOR]