Immobilization of mannanase on sodium alginate-grafted-β-cyclodextrin: An easy and cost effective approach for the improvement of enzyme properties

Research and application progress of microbial β-mannanases: a mini-review

Mannan is a predominant constituent of cork hemicellulose and is widely distributed in various plant tissues. β-Mannanase is the principal mannan-degrading enzyme, which breaks down the β-1,4-linked mannosidic bonds in mannans in an endo-acting manner. Microorganisms are a valuable source of β-mannanase, which exhibits catalytic activity in a wide range of pH and temperature, making it highly versatile and applicable in pharmaceuticals, feed, paper pulping, biorefinery, and other industries. Here, the origin, classification, enzymatic properties, molecular modification, immobilization, and practical applications of microbial β-mannanases are reviewed, the future research directions for microbial β-mannanases are also outlined.

A systematic study on the characteristics and applications of laccases produced by fungi: insights on their potential for biotechnologies

Laccases are polyphenol oxidase enzymes and form the enzyme complex known for their role in wood decomposition and lignin degradation. The present study aimed to systematically review the state-of-the-art trends in scientific publications on laccase enzymes of the last 10 years. The main aspects checked included the laccase-producing fungal genera, the conditions of fungal growth and laccase production, the methods of immobilization, and potential applications of laccase. After applying the systematic search method 177 articles were selected to compound the final database. Although various fungi produce laccase, most studies were Trametes and Pleurotus genera. The submerged fermentation (SmF) has been the most used, however, the use of solid-state fermentation (SSF) appeared as a promising technique to produce laccase when using agro-industrial residues as substrates. Studies on laccase immobilization showed the covalent bonding and entrapment methods were the most used, showing greater efficiency of immobilization and a high number of enzyme reuses. The main use of the laccase was in bioremediation, especially in the discoloration of dyes from the textile industry and the degradation of pharmaceutical waste. Implications and consequences of all these findings in biotechnology and environment, as well as the trends and gaps of laccase research were discussed.

Magnetic core-shell cellulose system for the oriented immobilization of a recombinant β-galactosidase with a protein tag

The objective of this study was to immobilize a recombinant β-galactosidase (Gal) tagged with a cellulose-binding domain (CBD) onto a magnetic core-shell (CS) cellulose system. After 30 min of reaction, 4 U/capsule were immobilized (CS@Gal), resulting in levels of yield and efficiency exceeding 80 %. The optimal temperature for β-galactosidase-CBD activity increased from 40 to 50 °C following oriented immobilization. The inhibitory effect of galactose decreased in the enzyme reactions catalyzed by CS@Gal, and Mg2+ increased the immobilized enzyme activity by 40 % in the magnetic CS cellulose system. The relative enzyme activity of the CS@Gal was 20 % higher than that of the soluble enzyme activity after 20 min at 50 °C. The CS support and CS@Gal capsules exhibited an average size of 8 ± 1 mm, with the structure of the shell (alginate-pectin-cellulose) enveloping and isolating the magnetic core. The immobilized β-galactosidase-CBD within the magnetic CS cellulose system retained ∼80 % of its capacity to hydrolyze lactose from skim milk after 10 reuse cycles. This study unveils a novel and promising support for the oriented immobilization of recombinant β-galactosidase using a magnetic CS system and a CBD tag. This support facilitates β-galactosidase reuse and efficient separation, consequently enhancing the catalytic properties of the enzyme.

In vitro assessment of the immobilized mannanase enzyme against infection-causing Candida

Background: Developing an effective treatment for fungal infections is among contemporary medicine's challenges. In this study we aimed to eradicate mannan in pathogenic Candidae's cell walls using a nontoxic method, mannanase. Materials & Methods: We investigated the in vitro antifungal activities of mannanase immobilized on zinc oxide nanoparticles (ZnONps) and reduced graphene oxide nanoparticles (RGONps), as well as therapeutics against Candidae. Mannanase was purified from Bacillus invictae (activity: 5.15 EU/ml; range: 60-80%) and then immobilized it to ZnO and RGO to enhance its effectiveness. Results: Mannanase immobilized on ZnONps had the highest activity, with a value of 4.97 EU/ml, more effective than amphotericin-B. However, it could not reach the inhibition rates of other antifungals. Conclusion: Mannanase immobilized on ZnONps could be an effective fungicide for Candida biocontrol.

Enhanced Enzymatic Performance of β-Mannanase Immobilized on Calcium Alginate Beads for the Generation of Mannan Oligosaccharides

Mannan oligosaccharides (MOSs) are excellent prebiotics that are usually obtained via the enzymatic hydrolysis of mannan. In order to reduce the cost of preparing MOSs, immobilized enzymes that demonstrate good performance, require simple preparation, and are safe, inexpensive, and reusable must be developed urgently. In this study, β-mannanase was immobilized on calcium alginate (CaAlg). Under the optimal conditions of 320 U enzyme addition, 1.6% sodium alginate, 2% CaCl2, and 1 h of immobilization time, the immobilization yield reached 68.3%. The optimum temperature and pH for the immobilized β-mannanase (Man-CaAlg) were 75 °C and 6.0, respectively. The Man-CaAlg exhibited better thermal stability, a high degree of pH stability, and less substrate affinity than free β-mannanase. The Man-CaAlg could be reused eight times and retained 70.34% of its activity; additionally, the Man-CaAlg showed 58.17% activity after 30 days of storage. A total of 7.94 mg/mL of MOSs, with 4.94 mg/mL of mannobiose and 3.00 mg/mL of mannotriose, were generated in the oligosaccharide production assay. It is believed that this convenient and safe strategy has great potential in the important field of the use of immobilized β-mannanase for the production of mannan oligosaccharides.

Biodegradable and hemocompatible alginate/okra hydrogel films with promising stability and biological attributes

Currently, combinations of natural polymers and semi-synthetic biomolecules have gained attention for food-packaging, drug delivery, coatings, and biomedical applications. In this work, cross-linking property of two biopolymers was employed for the fabrication of hydrogel films. Sodium alginate (SAlg) and Okra gel (OkG) were used in different ratios (95:05, 75:25 and 85:15) to synthesize hydrogel films by solvent-casting method. Formation of the films was confirmed by FTIR and Raman techniques which specified the interaction between biomolecules of SAlg and OkG. XRD pattern has shown the presence of both amorphous and micro-crystalline phases in the hydrogel films and SEM studies have shown porosity, amorphousness and agglomerated morphology. TGA and DSC analyses revealed degradation of the film at 420 °C and stability studies using PBS buffer indicated stability and hydrophilic nature of hydrogel films. In-vitro degradation test was also performed for 10 weeks through the incubation of hydrogel-films in simulated body fluid and the effect of pH and temperature was also studied. Results have shown worth-some influence of okra gel on the fabricated films. Hemolytic and antioxidant activities of the gels were also determined and being non-toxic, all these ratios were found suitable for biomedical applications; especially 85:15 have shown maximum potential.

Immobilized glucoamylase based on ZIF-8: Preparation, response surface optimization, characterization

The glucoamylase@ZIF-8 was prepared using ZIF-8 material as the carrier in this study. The preparation process was optimized by response surface methodology, and the stability of glucoamylase@ZIF-8 was determined. The material was characterized by scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. The results showed that the optimum preparation process of glucoamylase@ZIF-8 was 1.65 mol 2-methylimidazole, 5.85 mL glucoamylase, 33°C stirring temperature, 90 min stirring time, and 84.0230% ± 0.6006% embedding rate. At 100°C, the free glucoamylase completely lost its activity, whereas the glucoamylase@ZIF-8 still had a retained enzyme activity of 12.0123% ± 0.86158%; at pH 3-6, the highest activity of glucoamylase@ZIF-8 was 95.9531% ± 0.96181%, and about 80% of glucoamylase activity could be retained under alkaline conditions. When the ethanol concentration was 13%, the retained enzyme activity was 7.9316% ± 0.19805%, significantly higher than free enzymes. The K_m of glucoamylase@ZIF-8 and free enzyme were 1235.6825 and 80.317 mg/mL, respectively. V_max was 0.2453 and 0.149 mg/(mL min), respectively. The appearance, crystal strength, and thermal stability of glucoamylase@ZIF-8 were improved after optimization, and they had high reusability.

Immobilization of Enzymes on Cyclodextrin-Anchored Dehiscent Mesoporous TiO2 for Efficient Photoenzymatic Hydroxylation

A three-in-one heterogeneous catalyst (UPO@dTiO₂-CD) was fabricated by grafting cyclodextrins (CDs) on the dehiscent TiO₂ (dTiO₂) surface and subsequently immobilizing unspecific peroxygenase (rAaeUPO), which exhibited double enhanced electron/mass transfer in photo-enzymatic enantioselective hydroxylation of the C-H bond. The tunable anatase/rutile phase ratio and dehiscent mesoporous architectures of dTiO₂ and the electron donor feature and hydrophobic inner cavity of the CDs are independently responsible for accelerating both electron and mass transfer. The coordination of the photocatalytic and enzymatic steps was achieved by structural and compositional regulation. The optimized UPO@dTiO₂-CD not only displayed high catalytic efficiency (turnover number and turnover frequency of rAaeUPO up to >65,000 and 91 min^-1, respectively) but also exhibited high stability and reusability.

Tailor-made novel electrospun polycaprolactone/polyethyleneimine fiber membranes for laccase immobilization: An all-in-one material to biodegrade textile dyes and phenolic compounds

In spite of many works on the biodegradation of textile dyes and phenolic compounds, we propose a new, inexpensive, environmentally friendly, and sustainable material based on electrospun fiber and immobilized laccase. The polycaprolactone (PCL)/polyethyleneimine (PEI) electrospun fibers were optimized and prepared by electrospinning technique according to the operational parameters like PCL concentration (12 wt%), PEI concentration (10 wt%), voltage (16 kV), needle tip-collector distance (20 cm), and injection speed (0.7 mL/h). Next, characterization studies were performed to investigate the morphology and structure of the electrospun fibers without and with laccase. The crude laccase was obtained by cultivating the white rot fungus T. trogii (TT), and T. versicolor (TV). The resulting electrospun fibers showed a smooth surface with a mean diameter of around 560 nm, and larger diameters were observed after laccase immobilization. According to the results, immobilization increased the stability properties of laccase such as storage, and operational. For instance, the residual activity of the PCL/PEI/TTL and PCL/PEI/TVL after 10 repeated cycles, was 33.2 ± 0.2% and 26.0 ± 0.9%, respectively. After 3 weeks of storage, they retained around 30% of their original activity. Moreover, the PCL/PEI/TTL and PCL/PEI/TVL were found to possess high decolorization yield to remove Orange II and Malachite Green textile dyes from solutions imitating polluted waters. Among them, the PCL/PEI/TTL exhibited the highest decolorization efficiencies of Orange II and Malachite Green after 8 continuous uses at pH 5 and a temperature of 50 °C, reaching over 86%, and 46%, respectively. Moreover, PCL/PEI/TTL and PCL/PEI/TVL effectively degraded the 2,6-dichlorophenol phenolic compound at an optimal pH and temperature range and exhibited maximum removal efficiency of 52.6 ± 0.1% and 64.5 ± 7.6%, respectively. Our approach combines the advantageous properties of electrospun fiber material and immobilization strategy for the efficient use of industrial scale important enzymes such as laccase in various enzymatic applications.

Immobilization of lipase on silica nanoparticles by adsorption followed by glutaraldehyde cross-linking

In this study, Candida antarctica lipase B was immobilized on silica (SiO₂) nanoparticles by physical adsorption, and then cross-linked with glutaraldehyde (GA) to prepare cross-linked immobilized lipase (CLIL). During the condition of 1.28 mg/mL lipase concentration, 25 ℃ temperature, 2 h adsorption time, 0.01% GA (V/V) 7.5 mL and 2 h cross-linking time, the highest recovery activity of CLIL reached 87.82 ± 0.07% (22.55 ± 0.025 U/mg). Scanning electron microscope (SEM) and confocal laser scanning microscope (CLSM) confirmed that lipase was immobilized on the surface of SiO₂ nanoparticles. The changes in secondary structures of CLIL indicated that cross-linking changed the secondary structure of lipase protein, which made the structure of CLIL more stable. Compared with the free lipase, the thermal stability and storage stability of CLIL was significantly improved, and the t_1/2 at 60 °C was extended. Studies had shown that it was a feasible method to obtain CLIL by cross-linking after adsorbing lipase on SiO₂ nanoparticles.

Polymer/Enzyme Composite Materials—Versatile Catalysts with Multiple Applications

A significant interest was granted lately to enzymes, which are versatile catalysts characterized by natural origin, with high specificity and selectivity for particular substrates. Additionally, some enzymes are involved in the production of high-valuable products, such as antibiotics, while others are known for their ability to transform emerging contaminates, such as dyes and pesticides, to simpler molecules with a lower environmental impact. Nevertheless, the use of enzymes in industrial applications is limited by their reduced stability in extreme conditions and by their difficult recovery and reusability. Rationally, enzyme immobilization on organic or inorganic matrices proved to be one of the most successful innovative approaches to increase the stability of enzymatic catalysts. By the immobilization of enzymes on support materials, composite biocatalysts are obtained that pose an improved stability, preserving the enzymatic activity and some of the support material’s properties. Of high interest are the polymer/enzyme composites, which are obtained by the chemical or physical attachment of enzymes on polymer matrices. This review highlights some of the latest findings in the field of polymer/enzyme composites, classified according to the morphology of the resulting materials, following their most important applications.

Modifying Thermostability and Reusability of Hyperthermophilic Mannanase by Immobilization on Glutaraldehyde Cross-Linked Chitosan Beads

In the current study, the purified β-mannanase (Man/Cel5B) from Thermotoga maritima was immobilized on glutaraldehyde cross-linked chitosan beads. The immobilization of Man/Cel5B on chitosan beads was confirmed by Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analysis. After immobilization, the protein loading efficiency and immobilization yield were found to be 73.3% and 71.8%, respectively. The optimum pH for both free and immobilized enzymes was found to be pH 5.5. However, the optimum temperature of immobilized Man/Cel5B increased by 10 °C, from 85 °C (free Man/Cel5B) to 95 °C (Immobilized). The half-life of free and immobilized enzymes was found to be 7 h and 9 h, respectively, at 85 °C owing to the higher thermostability of immobilized Man/Cel5B. The increase in thermostability was also demonstrated by an increase in the energy of deactivation (209 kJmol⁻¹) for immobilized enzyme compared to its native form (92 kJmol⁻¹), at 85 °C. Furthermore, the immobilized Man/Cel5B displayed good operational stability as it retained 54% of its original activity after 15 repeated catalytic reactions concerning its free form.

Design of laccase-metal-organic framework hybrid constructs for biocatalytic removal of textile dyes

This study aims to present a simple and effective carrier matrix to immobilize laccase as opposed to complex and tedious immobilization processes and also to use it in the removal of textile dyes. For this purpose, Cobalt (Co) and Copper (Cu) based metal-organic frameworks (MOFs) were prepared and laccase was immobilized on two different MOFs via encapsulation. The characterization outcomes showed that laccase was well immobilized into MOF supports. Optimum pH and temperature were found for Lac/Co-MOF (pH 4.5 at 50 °C) and Lac/Cu-MOF (pH 5.0 at 50 °C). The Km (0.03 mM) and Vmax (97.4 μmol/min) values of Lac/Cu-MOF were lower than those of Lac/Co-MOF (Km = 0.13 mM, Vmax = 230.7 μmol/min). The immobilized laccases showed good reusability as well as improved resistance to temperature denaturation and high storage stability. For instance, the Lac/Co-MOF and Lac/Cu-MOF retained more than 58% activity after 4 weeks of storage at room temperature. Meanwhile, Lac/Co-MOF and Lac/Cu-MOF maintained 56.5% and 55.8% of their initial activity, respectively, after 12 reuse cycles. Moreover, thermal deactivation kinetic studies of immobilized laccases displayed lower k value, higher t_1/2, and enhancement of thermodynamic parameters, which means better thermostability. Finally, the decolorization activities for the Lac/Co-MOF were 78% and 61% at the 5th cycle for Reactive Blue 171 and Reactive Blue 198, respectively. In conclusion, it can be inferred that the MOFs are more sustainable and beneficial support for laccase immobilization and they can be efficient for removing textile dyes from industrial wastes.

Synthesis of two novel bio-based hydrogels using sodium alginate and chitosan and their proficiency in physical immobilization of enzymes

Herein, four novel and bio-based hydrogel samples using sodium alginate (SA) and chitosan (CH) grafted with acrylamide (AAm) and glycidyl methacrylate (GMA) and their reinforced nanocomposites with graphene oxide (GO) were synthesized and coded as SA-g-(AAm-co-GMA), CH-g-(AAm-co-GMA), GO/SA-g-(AAm-co-GMA), and GO/CH-g-(AAm-co-GMA), respectively. The morphology, net charge, and water absorption capacity of samples were entirely changed by switching the biopolymer from SA to CH and adding a nano-filler. The proficiencies of hydrogels were compared in the immobilization of a model metagenomic-derived xylanase (PersiXyn9). The best performance was observed for GO/SA-g-poly(AAm-co-GMA) sample indicating better stabilizing electrostatic attractions between PersiXyn9 and reinforced SA-based hydrogel. Compared to the free enzyme, the immobilized PersiXyn9 on reinforced SA-based hydrogel showed a 110.1% increase in the released reducing sugar and almost double relative activity after 180 min storage. While immobilized enzyme on SA-based hydrogel displayed 58.7% activity after twelve reuse cycles, the enzyme on CH-based carrier just retained 8.5% activity after similar runs.

Operational Stability, Regenerability, and Thermodynamics Studies on Biogenic Silica/Magnetite/Graphene Oxide Nanocomposite-Activated Candida rugosa Lipase

Inorganic biopolymer-based nanocomposites are useful for stabilizing lipases for enhanced catalytic performance and easy separation. Herein, we report the operational stability, regenerability, and thermodynamics studies of the ternary biogenic silica/magnetite/graphene oxide nanocomposite (SiO₂/Fe₃O₄/GO) as a support for Candida rugosa lipase (CRL). The X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), field-electron scanning electron microscopy (FESEM), vibrating sample magnetometry (VSM), and nitrogen adsorption/desorption data on the support and biocatalyst corroborated their successful fabrication. XPS revealed the Fe₃O₄ adopted Fe²⁺ and Fe³⁺ oxidation states, while XRD data of GO yielded a peak at 2θ = 11.67°, with the SiO₂/Fe₃O₄/GO revealing a high surface area (≈261 m²/g). The fourier transform infrared (FTIR) spectra affirmed the successful fabricated supports and catalyst. The half-life and thermodynamic parameters of the superparamagnetic immobilized CRL (CRL/SiO₂/Fe₃O₄/GO) improved over the free CRL. The microwave-regenerated CRL/SiO₂/Fe₃O₄/GO (≈82%) exhibited higher catalytic activity than ultrasonic-regenerated (≈71%) ones. Lower activation (Ea) and higher deactivation energies (Ed) were also noted for the CRL/SiO₂/Fe₃O₄/GO (13.87 kJ/mol, 32.32 kJ/mol) than free CRL (15.26 kJ/mol, 27.60 kJ/mol). A peak at 4.28 min in the gas chromatograph-flame ionization detection (GC-FID) chromatogram of the purified ethyl valerate supported the unique six types of 14 hydrogen atoms of the ester (CAS: 539-82-2) in the proton nuclear magnetic resonance (¹H-NMR) data. The results collectively demonstrated the suitability of SiO₂/Fe₃O₄/GO in stabilizing CRL for improved operational stability and thermodynamics and permitted biocatalyst regenerability.

Nano-organic supports for enzyme immobilization: Scopes and perspectives

A variety of organic nanomaterials and organic polymers are used for enzyme immobilization to increase enzymes stability and reusability. In this study, the effects of the immobilization of enzymes on organic and organic-inorganic hybrid nano-supports are compared. Immobilization of enzymes on organic support nanomaterials was reported to significantly improve thermal, pH and storage stability, acting also as a protection against metal ions inhibitory effects. In particular, the effects of enzyme immobilization on reusability, physical, kinetic and thermodynamic parameters were considered. Due to their biocompatibility with low health risks, organic support nanomaterials represent a good choice for the immobilization of enzymes. Organic nanomaterials, and especially organic-inorganic hybrids, can significantly improve the kinetic and thermodynamic parameters of immobilized enzymes compared to macroscopic supports. Moreover, organic nanomaterials are more environment friendly for medical applications, such as prodrug carriers and biosensors. Overall, organic hybrid nanomaterials are receiving increasing attention as novel nano-supports for enzyme immobilization and will be used extensively.