Evaluation of a silica-coated magnetic nanoparticle for the immobilization of a His-tagged lipase

Biocatalysis for Rare Ginsenoside Rh2 Production in High Level with Co-Immobilized UDP-Glycosyltransferase Bs-YjiC Mutant and Sucrose Synthase AtSuSy

Rare ginsenoside Rh2 exhibits diverse pharmacological effects. UDP-glycosyltransferase (UGT) catalyzed glycosylation of protopanaxadiol (PPD) has been of growing interest in recent years. UDP-glycosyltransferase Bs-YjiC coupling sucrose synthase in one-pot reaction was successfully applied to ginsenoside biosynthesis with UDP-glucose regeneration from sucrose and UDP, which formed a green and sustainable approach. In this study, the his-tagged UDP-glycosyltransferase Bs-YjiC mutant M315F and sucrose synthase AtSuSy were co-immobilized on heterofunctional supports. The affinity adsorption significantly improved the capacity of specific binding of the two recombinant enzymes, and the dual enzyme covalently cross-linked by the acetaldehyde groups significantly promoted the binding stability of the immobilized bienzyme, allowing higher substrate concentration by easing substrate inhibition for the coupled reaction. The dual enzyme amount used for ginsenoside Rh2 biosynthesis is Bs-YjiC-M315F: AtSuSy = 18 mU/mL: 25.2 mU/mL, a yield of 79.2% was achieved. The coimmobilized M315F/AtSuSy had good operational stability of repetitive usage for 10 cycles, and the yield of ginsenoside Rh2 was kept between 77.6% and 81.3%. The high titer of the ginsenoside Rh2 cumulatively reached up to 16.6 mM (10.3 g/L) using fed-batch technology, and the final yield was 83.2%. This study has established a green and sustainable approach for the production of ginsenoside Rh2 in a high level of titer, which provides promising candidates for natural drug research and development.

Manipulation of nanofiber-based β-galactosidase nanoenvironment for enhancement of galacto-oligosaccharide production

The nanoenvironment of nanobiocatalysts, such as local hydrophobicity, pH and charge density, plays a significant role in optimizing the enzymatic selectivity and specificity. In this study, Kluyveromyces lactis β-galactosidase (Gal) was assembled onto polystyrene nanofibers (PSNFs) to form PSNF-Gal nanobiocatalysts. We proposed that local hydrophobicity on the nanofiber surface could expel water molecules so that the transgalactosylation would be preferable over hydrolysis during the bioconversion of lactose, thus improve the galacto-oligosaccharides (GOS) yield. PSNFs were fabricated by electro-spinning and the operational parameters were optimized to obtain the nanofibers with uniform size and ordered alignment. The resulting nanofibers were functionalized for enzyme immobilization through a chemical oxidation method. The functionalized PSNF improved the enzyme adsorption capacity up to 3100 mg/g nanofiber as well as enhanced the enzyme stability with 80% of its original activity. Importantly, the functionalized PSNF-Gal significantly improved the GOS yield and the production rate was up to 110 g/l/h in comparison with 37 g/l/h by free β-galactosidase. Our research findings demonstrate that the localized nanoenvironment of the PSNF-Gal nanobiocatalysts favour transgalactosylation over hydrolysis in lactose bioconversion.

Preparation and Characterization of Double Shell Fe3O4 Cluster@Nonporous SiO2@Mesoporous SiO2 Nanocomposite Spheres and Investigation of their In Vitro Biocompatibility

BACKGROUND

Multifunctional core-shell magnetic nanocomposite particles with tunable characteristics have been paid much attention for biomedical applications in recent years. A rational design and suitable preparation method must be employed to be able to exploit attractive properties of magnetic nanocomposite particles.

OBJECTIVES

Herein, we report on a simple approach for the synthesis of magnetic mesoporous silica nanocomposite particles (MMSPs), consisted of a Fe₃O₄ cluster core, a nonporous silica shell and a second shell of the mesoporous silica of suitable sizes for biomedical applications and evaluate their cytotoxicity effects on human cancer prostate cell lines.

MATERIALS AND METHODS

Clusters of magnetite (Fe₃O₄) nanoparticles were coated by a layer of nonporous silica using Stöber method. The coating step was completed by an outer layer of mesoporous silica via template-removing method. Structural properties of MMSPs were investigated by FTIR, HR-S(T)EM, BET, XRD techniques and magnetic properties of MMSPs by VSM instrument. MTT and LDH assays were employed to study the cytotoxicity of MMSPs.

RESULTS

Obtained results revealed that decreasing the precursor concentration and the reaction time at the nonporous silica shell formation step decreases the thickness of the nonporous silica shell and consequently leads to the formation of smaller MMSPs. The as-prepared MMSPs have a desirable average size of 180±10 nm, an average pore size of 3.01 nm, a high surface area of 390.4 m².g^-1 and a large pore volume of 0.294 cm³.g^-1. In addition, the MMSPs exhibited a superparamagnetic behavior and a high magnetization saturation value of 21±0.5 emu/g. Furthermore, the viability tests of DU-145 cell lines exposed to various concentrations of these particles demonstrated negligible cytotoxicity effects of the as-prepared particles.

CONCLUSIONS

These results demonstrate interesting properties of MMSPs prepared in this study for biomedical applications.

Nanobiocatalyst advancements and bioprocessing applications

The nanobiocatalyst (NBC) is an emerging innovation that synergistically integrates advanced nanotechnology with biotechnology and promises exciting advantages for improving enzyme activity, stability, capability and engineering performances in bioprocessing applications. NBCs are fabricated by immobilizing enzymes with functional nanomaterials as enzyme carriers or containers. In this paper, we review the recent developments of novel nanocarriers/nanocontainers with advanced hierarchical porous structures for retaining enzymes, such as nanofibres (NFs), mesoporous nanocarriers and nanocages. Strategies for immobilizing enzymes onto nanocarriers made from polymers, silicas, carbons and metals by physical adsorption, covalent binding, cross-linking or specific ligand spacers are discussed. The resulting NBCs are critically evaluated in terms of their bioprocessing performances. Excellent performances are demonstrated through enhanced NBC catalytic activity and stability due to conformational changes upon immobilization and localized nanoenvironments, and NBC reutilization by assembling magnetic nanoparticles into NBCs to defray the high operational costs associated with enzyme production and nanocarrier synthesis. We also highlight several challenges associated with the NBC-driven bioprocess applications, including the maturation of large-scale nanocarrier synthesis, design and development of bioreactors to accommodate NBCs, and long-term operations of NBCs. We suggest these challenges are to be addressed through joint collaboration of chemists, engineers and material scientists. Finally, we have demonstrated the great potential of NBCs in manufacturing bioprocesses in the near future through successful laboratory trials of NBCs in carbohydrate hydrolysis, biofuel production and biotransformation.

Current Trends in Nanomaterial-Based Amperometric Biosensors

The last decade has witnessed an intensive research effort in the field of electrochemical sensors, with a particular focus on the design of amperometric biosensors for diverse analytical applications. In this context, nanomaterial integration in the construction of amperometric biosensors may constitute one of the most exciting approaches. The attractive properties of nanomaterials have paved the way for the design of a wide variety of biosensors based on various electrochemical detection methods to enhance the analytical characteristics. However, most of these nanostructured materials are not explored in the design of amperometric biosensors. This review aims to provide insight into the diverse properties of nanomaterials that can be possibly explored in the construction of amperometric biosensors.

Optimizing the biocatalytic productivity of an engineered sialidase from Trypanosoma rangeli for 3'-sialyllactose production

An engineered sialidase, Tr6, from Trypanosoma rangeli was used for biosynthetic production of 3'-sialyllactose, a human milk oligosaccharide case compound, from casein glycomacropeptide (CGMP) and lactose, components abundantly present in industrial dairy side streams. Four different enzyme re-use methods were compared to optimize the biocatalytic productivity, i.e. 3'-sialyllactose formation per amount of Tr6 employed: (i) His-tag immobilization on magnetic Cu²⁺-iminodiacetic acid-functionalized nanoparticles (MNPs), (ii) membrane immobilization, (iii) calcium alginate encapsulation of cross-linked Tr6, and (iv) Tr6 catalysis in a membrane reactor. Tr6 immobilized on MNPs gave a biocatalytic productivity of 84 mg 3'-sialyllactose/mg Tr6 after seven consecutive reaction runs. Calcium-alginate and membrane immobilization were inefficient. Using free Tr6 in a 10 kDa membrane reactor produced a 9-fold biocatalytic productivity increase compared to using free Tr6 in a batch reactor giving 306 mg 3'-sialyllactose/mg Tr6 after seven consecutive reaction runs. The 3'-sialyllactose yield on α-2,3-bound sialic acid in CGMP was 74%. Using circular dichroism, a temperature denaturation midpoint of Tr6, Tm, of 57.2 °C was determined. The thermal stability of free Tr6 was similarly high and the Tr6 was stable at the reaction temperature (25 °C) for at least 24 h.