Preparation and Biochemical Characterization of Penicillium crustosum Thom P22 Lipase Immobilization Using Adsorption, Encapsulation, and Adsorption-Encapsulation Approaches

This work describes the immobilization and the characterization of purified Penicillium crustosum Thom P22 lipase (PCrL) using adsorption, encapsulation, and adsorption-encapsulation approaches. The maximum activity of the immobilized PCrL on CaCO3 microspheres and sodium alginate beads was shifted from 37 to 45 °C, compared with that of the free enzyme. When sodium alginate was coupled with zeolite or chitosan, the immobilization yield reached 100% and the immobilized PCrL showed improved stability over a wide temperature range, retaining all of its initial activity after a one-hour incubation at 60 °C. The immobilization of PCrL significantly improves its catalytic performance in organic solvents, its pH tolerance value, and its thermal stability. Interestingly, 95% and almost 50% of PCrL's initial activity was retained after 6 and 12 cycles, respectively. The characteristics of all PCrL forms were analyzed by X-ray diffraction and scanning electron microscopy combined with energy dispersive spectroscopy. The maximum conversion efficiency of oleic acid and methanol to methyl esters (biodiesel), by PCrL immobilized on CaCO3, was 65% after a 12 h incubation at 40 °C, while free PCrL generated only 30% conversion, under the same conditions.

Immobilization of Alcalase on Silica Supports Modified with Carbosilane and PAMAM Dendrimers

Enzyme immobilization is a powerful strategy for enzyme stabilization and recyclability. Materials covered with multipoint molecules are very attractive for this goal, since the number of active moieties to attach the enzyme increases with respect to monofunctional linkers. This work evaluates different dendrimers supported on silica to immobilize a protease enzyme, Alcalase. Five different dendrimers were employed: two carbosilane (CBS) dendrimers of different generations (SiO₂-G₀Si-NH₂ and SiO₂-G₁Si-NH₂), a CBS dendrimer with a polyphenoxo core (SiO₂-G₁O₃-NH₂), and two commercial polyamidoamine (PAMAM) dendrimers of different generations (SiO₂-G₀PAMAM-NH₂ and SiO₂-G₁PAMAM-NH₂). The results were compared with a silica support modified with a monofunctional molecule (2-aminoethanethiol). The effect of the dendrimer generation, the immobilization conditions (immobilization time, Alcalase/SiO₂ ratio, and presence of Ca²⁺ ions), and the digestion conditions (temperature, time, amount of support, and stirring speed) on Alcalase activity has been evaluated. Enzyme immobilization and its activity were highly affected by the kind of dendrimer and its generation, observing the most favorable behavior with SiO₂-G₀PAMAM-NH₂. The enzyme immobilized on this support was used in two consecutive digestions and, unlike CBS supports, it did not retain peptides released in the digestion.

Zinc oxide nanoparticles-impregnated chitosan surfaces for covalent immobilization of trypsin: Stability & kinetic studies

Trypsin (Try, EC. 3.4.21.4) was effectively immobilized on the surface of glutaraldehyde(GA)-activated ZnO/Chitosan nanocomposite through covalent attachment via Schiff-base linkages. Size, structure, surface morphology, & percentage elemental composition of the prepared ZnO nanoparticles and chitosan-coated ZnO nanocomposite were studied by UV-Visible spectroscopy, Fourier-transform infrared spectroscopy (FTIR), X-Ray diffraction analysis (XRD), transmission electron microscopy (TEM), Scanning electron microscopy (SEM), and Energy-Dispersive X-Ray Microanalysis (EDAX) techniques. Optimal immobilization conditions (incubation time (16 h), enzyme concentration (1.8 mg/ml), and pH (7.8)) were investigated to obtain the maximum expressed activity of the immobilized trypsin. Immobilized & solubilized trypsin exhibited the optimum catalytic activity at pH 8.5, 60 °C, and pH 7.8, 45 °C respectively. Kinetic parameters (K_m, V_max) of immobilized (27.12 μM, 8.82 μM/min) & free trypsin (25.76 μM, 4.16 μM/min) were determined, indicating that efficiency of trypsin improves after immobilization. Immobilized trypsin preserved 67% of initial activity at 50 °C during 2 h of incubation & sustained nearly 50% of catalytic activity until the 9th repeated cycle of utilization. Moreover, immobilized trypsin retained 50% of enzymatic activity after 90 days of storage at 4 °C. Hence, the current findings suggest that ZnO/Chitosan-GA-Trypsin would be a promising biocatalyst for large-scale biotechnological applications.

Smart chemistry of enzyme immobilization using various support matrices - A review

The surface chemistry, pendent functional entities, and ease in tunability of various materials play a central role in properly coordinating with enzymes for immobilization purposes. Due to the interplay between the new wave of support matrices and enzymes, the development of robust biocatalytic constructs via protein engineering expands the practical scope and tunable catalysis functions. The concept of stabilization via functional entities manipulation, the surface that comprises functional groups, such as thiol, aldehyde, carboxylic, amine, and epoxy have been the important driving force for immobilizing purposes. Enzyme immobilization using multi-functional supports has become a powerful norm and presents noteworthy characteristics, such as selectivity, specificity, stability, resistivity, induce activity, reaction efficacy, multi-usability, high catalytic turnover, optimal yield, ease in recovery, and cost-effectiveness. There is a plethora of literature on traditional immobilization approaches, e.g., intramolecular chemical (covalent) attachment, adsorption, encapsulation, entrapment, and cross-linking. However, the existing literature is lacking state-of-the-art smart chemistry of immobilization. This review is a focused attempt to cover the literature gap of surface functional entities that interplay between support materials at large and enzyme of interest, in particular, to tailor robust biocatalysts to fulfill the growing and contemporary needs of several industrial sectors.

Mucin-1 conjugated polyamidoamine-based nanoparticles for image-guided delivery of gefitinib to breast cancer

PAMAM dendrimers (PAMs) are a group of polymeric macromolecules with distinctive physicochemical features, which can make them multifunctional theranostic nanoparticles (NPs). This study was designed to examine the impact of mucin-1 aptamer-conjugated NPs which were engineered using PAM for image-guided delivery of gefitinib (GEF) in the breast cancer cells/tumor. For this, PAMAM was conjugated with diethylenetriaminepentaacetic acid (DTPA) and modified with PEG2000 to prepare a multi-functionalized NPs. Subsequently, GEF was loaded onto the DTPA-PAM-PEG NPs, which were then armed with MUC-1 aptamer to form the DTPA-PAM-PEG/GEF@MUC-1 nanosystem. Finally, aptamer-conjugated NPs were radiolabeled by gallium-67 as an imaging agent to construct image-guided nanoplatforms. The prepared NPs were characterized by different techniques. The kinetic release models of gefitinib from radiolabeled NPs offer the sustained-release mechanism of the encapsulated drug for over 7 days. In vitro evaluation showed higher cytotoxicity and enhanced uptake of the mucin-grafted NPs in MCF-7 cells. Nuclear medicine imaging and in vivo investigations revealed significant accumulation of ⁶⁷Ga-DTPA-PAM-PEG/GEF@MUC-1 in the tumor site of the animal models. These data suggest that the engineered NPs are a promising image-guided nanosystem for mucin-expressing breast cells/tumors with the assistance of nuclear medicine.

Immobilization of thermolysin enzyme on dendronized silica supports. Evaluation of its feasibility on multiple protein hydrolysis cycles

This work evaluates different dendrimer-silica supports for the immobilization of enzymes by multipoint covalent binding. Thermolysin was immobilized on two dendrimers (PAMAM and carbosilane) with two different generations (zero (G0) and first (G1)). Results were compared with a control, a silica support functionalized with a monofunctional molecule. Dendrimers increased the number of available sites to bind the enzyme. Despite the enzyme was immobilized on all supports, G0 dendrimers immobilized a 30% more enzyme than G1. Thermolysin immobilized on G0 dendrimer supports showed the highest activity and could be employed in three consecutive hydrolysis cycles. Optimal immobilization time was 1 h while optimal protein loading was 25 mg enzyme/100 mg support. Enzyme activity was promoted when using 5 mg of immobilized enzyme at 750 rpm, 60 °C, and 2 h of hydrolysis. Under these conditions, the activity of thermolysin increased up to the 78% of the free enzyme activity. Kinetics of the hydrolysis reaction using the immobilized thermolysin was also studied and compared with the obtained using the free thermolysin. The addition of ZnCl₂ and NaCl during the immobilization procedure increased thermolysin activity in the second (22% more) and in the third (14% more) hydrolysis clycles.

Mitigation of bisphenol A using an array of laccase-based robust bio-catalytic cues - A review

Bisphenol A (BPA) is a known endocrine disruptor that poses concerning environmental and human-health related issues and ecological risks. It has been largely used as an intermediate in the manufacture of epoxy resins and polycarbonate plastics. Traces of BPA can reach into the environment through inadequate or inefficient removal during wastewater treatment, uncontrolled landfill leachates, and leaching out from the discarded BPA-based materials. Several physicochemical treatment methods including adsorption, Fenton, ozonation, electrochemical and photochemical degradation, and membrane filtration, have been applied for BPA elimination. However, these methods are not adequate for large-scale treatment due to some inherent limitations. Benefiting from high catalytic efficiency and specificity, enzyme-based bio-catalytic degradation strategies are considered quite meaningful alternative for efficient and effective BPA removal from different routes. Among various oxidoreductases, i.e., laccases exhibited a superior potential for the remediation of BPA-containing wastewater. Enzymatic oxidation of BPA can be boosted by using various natural or synthetic redox mediators. Immobilized enzymes can expand their applicability to continuous bioprocessing and facilitates process intensification. Therefore, optimized formulations of insolubilized biocatalysts are of strategic interest in the environmental biotechnology. In this review, recent research studies dealing with BPA removal by the laccase-catalyzed system are presented. At first, the presence of BPA in the ecosystem, sources, exposure, and its impact on the living organisms and human beings is summarized. Then, we highlighted the use of crude as well as immobilized laccases for the degradation of BPA. In addition to toxicity and estrogenicity removal studies, the unresolved challenges, concluding remarks, and possible future direction is proposed in this important research area. It is palpable from the literature reviewed that free as well as immobilized forms of laccases have displayed noteworthy potential for BPA removal from wastewater.

Mucin-1 aptamer-armed superparamagnetic iron oxide nanoparticles for targeted delivery of doxorubicin to breast cancer cells

Introduction: Superparamagnetic iron oxide nanoparticles (SPIONs) can be functionalized with various agents (e.g., targeting and therapeutic agents) and used for targeted imaging/therapy of cancer. In the present study, we engineered doxorubicin (DOX)-conjugated anti-mucin -1 (MUC-1) aptamer (Ap)-armed PEGylated SPIONs for targeted delivery of DOX molecules to the breast cancer MCF-7 cells. Methods: The SPIONs were synthesized using the thermal decomposition method and modified by polyethylene glycol (PEG) to maximize their biocompatibility and minimize any undesired cytotoxicity effects. Subsequently, DOX molecules were loaded onto the SPIONs, which were further armed with amine-modified MUC-1 aptamer by EDC/NHS chemistry. Results: The morphologic and size analyses of nanoparticles (NPs) by transmission electron microscopy (TEM) and dynamic light scattering (DLS) revealed spherical and monodisperse MNPs with a size range of 5-64 nm. The FT-IR spectrophotometry and 1 HNMR analysis confirmed the surface modification of NPs. The cytotoxicity assay of the aptamer-armed MNPs exhibited a higher death rate in the MUC-1 over-expressing MCF-7 cells as compared to the MUC-1 under-expressing MDA-MB-231 cells. The flow cytometry analysis of the engineered Ap-armed SPIONs revealed a higher uptake as compared to the SPIONs alone. Conclusion: Based on our findings, the anti-MUC-1 Ap-armed PEGylated SPIONs loaded with DOX molecules could serve as an effective multifunctional theranostics for simultaneous detection and eradication of MUC-1-positive breast cancer cells.

Laccase-immobilized dendritic nanofibrous membranes as a novel approach towards the removal of bisphenol A

Laccase enzymes from Rhus vernificera were covalently bound on hyperbranched polyethyleneimine/polyethersulfone (HPEI/PES) electrospun nanofibrous membranes and used for the removal of bisphenol A (BPA) from water. The laccase enzyme was anchored on the dendritic membranes through the abundant peripheral amine groups on the HPEI using glutaraldehyde as a crosslinker. The membranes were characterized with attenuated total reflectance-Fourier transform infrared spectroscopy, scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDS) and ultraviolet-visible spectroscopy and correlative light and electron microscopy (CLEM). Furthermore, contact-angle analyses, pure water flux measurements and rejection analyses were carried out. CLEM showed that the enzymes were uniformly dispersed on the nanofibres while SEM analysis revealed that the nanofibres had an average diameter of 354 ± 37 nm. EDS showed the presence of Cu, which is the active entity in laccase enzymes. The laccase-modified membranes were hydrophilic (50°-53° contact angle) and exhibited high BPA rejection of 89.6% as compared to the 52.4% demonstrated by pristine PES. The laccase-modified membranes also maintained a constant permeate flux (7.07 ± 5.54 L/m² h) throughout the filtration process. Recyclability studies indicated that the membranes still maintained a high BPA removal of up to 79% even after four filtration cycles.