Cross-linking of horseradish peroxidase adsorbed on polycationic films: utilization for direct dye degradation

Development of chia gum/alginate-polymer support for horseradish peroxidase immobilization and its application in phenolic removal

Chia gum's molecular structure with distinctive properties as well as the alginate-based hydrogel's three-dimensionally cross-linked structure can provide a potent matrix for immobilization of enzyme. Herein, chia gum (CG)/alginate (A)-polymeric complex was synthesized and employed as a support material for the immobilization of horseradish peroxidase (HRP). HRP was successfully immobilized on the developed ACG-polymeric support, and the highest immobilization recovery (75%) was observed at 1.0% CG and 2% A, pH 7.0, and 50 units of the enzyme. The structure, morphology, and thermal properties of the prepared ACG-HRP were demonstrated using Fourier Transform Infrared (FTIR), Scanning Electron Microscope, and Thermogravimetric (TGA) analyses. ACG-HRP showed a good reusability (60%) over ten reuses. The immobilized ACG-HRP displayed an acidic pH optimum (6.0), a higher temperature optimum (50 °C), and improved thermal stability (30-50 °C) compared to the soluble HRP at pH 7.0, 40 °C and (30-40 °C), respectively. ACG-HRP has a lower affinity for hydrogen peroxide (H2O2) and guaiacol and a higher oxidizing affinity for a number of phenolic substrates. The ACG-HRP demonstrated greater resistance to heavy metals, isopropanol, urea, Triton X-100, and urea, as well as improved efficiency for eliminating phenol and p-chlorophenol. The developed ACG-polymeric support provided improved enzyme properties, allowed the reuse of the immobilized HRP in 10 cycles, and made it promising for several biotechnological applications.

Immobilization of Horseradish Peroxidase on Ca Alginate-Starch Hybrid Support: Biocatalytic Properties and Application in Biodegradation of Phenol Red Dye

In this study, horseradish peroxidase was extracted, purified, and immobilized on a calcium alginate-starch hybrid support by covalent bonding and entrapment. The immobilized HRP was used for the biodegradation of phenol red dye. A 3.74-fold purification was observed after precipitation with ammonium sulfate and dialysis. An immobilization yield of 88.33%, efficiency of 56.89%, and activity recovery of 50.26% were found. The optimum pH and temperature values for immobilized and free HRP were 5.0 and 50 °C and 6.5 and 60 °C, respectively. The immobilized HRP showed better thermal stability than its free form, resulting in a considerable increase in half-life time (t1/2) and deactivation energy (Ed). The immobilized HRP maintained 93.71% of its initial activity after 45 days of storage at 4 °C. Regarding the biodegradation of phenol red, immobilized HRP resulted in 63.57% degradation after 90 min. After 10 cycles of reuse, the immobilized HRP was able to maintain 43.06% of its initial biodegradative capacity and 42.36% of its enzymatic activity. At the end of 15 application cycles, a biodegradation rate of 8.34% was observed. In conclusion, the results demonstrate that the immobilized HRP is a promising option for use as an industrial biocatalyst in various biotechnological applications.

Enzyme Immobilization Technologies and Industrial Applications

Enzymes play vital roles in diverse industrial sectors and are essential components of many industrial products. Immobilized enzymes possess higher resistance to environmental changes and can be recovered/recycled easily when compared to the free forms. The primary benefit of immobilization is protecting the enzymes from the harsh environmental conditions (e.g., elevated temperatures, extreme pH values, etc.). The immobilized enzymes can be utilized in various large-scale industries, e.g., medical, food, detergent, textile, and pharmaceutical industries, besides being used in water treatment plants. According to the required application, a suitable enzyme immobilization technique and suitable carrier materials are chosen. Enzyme immobilization techniques involve covalent binding, encapsulation, entrapment, adsorption, etc. This review mainly covers enzyme immobilization by various techniques and their usage in different industrial applications starting from 1992 until 2022. It also focuses on the multiscale operation of immobilized enzymes to maximize yields of certain products. Lastly, the severe consequence of the COVID-19 pandemic on global enzyme production is briefly discussed.

Biological remediation technologies for dyes and heavy metals in wastewater treatment: New insight

The pollution of the environment caused by dyes and heavy metals emitted by industries has become a worldwide problem. The development of efficient, environmentally acceptable, and cost-effective methods of wastewater treatment containing dyes and heavy metals is critical. Biologically based techniques for treating effluents are fascinating since they provide several benefits over standard treatment methods. This review assesses the most recent developments in the use of biological based techniques to remove dyes and heavy metals from wastewater. The remediation of dyes and heavy metals by diverse microorganisms such as algae, bacteria, fungi and enzymes are depicted in detail. Ongoing biological method's advances, scientific prospects, problems, and the future prognosis are all highlighted. This review is useful for gaining a better integrated view of biological based wastewater treatment and for speeding future research on the function of biological methods in water purification applications.

A novel approach to efficient degradation of indole using co-immobilized horseradish peroxidase-syringaldehyde as biocatalyst

Biocatalytic degradation technology has received a great deal of attention in water treatment because of its advantages of high efficiency, environmental friendliness, and no secondary pollution. Herein, for the first time, horseradish peroxidase and mediator syringaldehyde were co-immobilized into functionalized calcium alginate composite beads grafted with glycidyl methacrylate and dopamine. The resultant biocatalyst of the co-immobilized horseradish peroxidase-syringaldehyde system has displayed excellent catalytic performance to degrade indole in water. The degradation rate of 100% was achieved in the presence of hydrogen peroxide even if the indole concentration was changing from 25 mg/L to 500 mg/L. If only the free enzyme was used under the identical water treatment conditions, the degradation of indole could hardly be observed even when the concentration of indole is low at 25 mg/L. This was attributed to the effective co-immobilization of the enzyme and the mediator so that the catalytic activity of horseradish peroxidase and the synergistic catalytic action of syringaldehyde could be fully developed. Furthermore, while the spherical catalyst was operated in succession and reused for four cycles in 50 mg/L indole solution, the degradation rate remained 91.8% due to its considerable reusability. This research demonstrated and provided a novel biocatalytic approach to degrade indole in water by the co-immobilized horseradish peroxidase-syringaldehyde system as biocatalyst.

Encapsulation of pectinase within polyacrylamide gel: characterization of its catalytic properties for continuous industrial uses

Pectinase as a biocatalyst play a significant role in food and textile industries. In this study, the pectinase was immobilized by encapsulation within polyacrylamide gel to enhance its catalytic properties and ensure the reusability for continuous industrial processes. 9.5% acrylamide and 0.5% N, N′- methylenebisacrylamide concentration gave high percentage of pectinase immobilization yield within gel. The catalytic properties of immobilized pectinase was determined with comparison of soluble pectinase. The immobilization of pectinase within polyacrylamide gel didn't effect catalytic properties of pectinase and both the free and immobilized pectinase showed maximum pectinolytic activity at 45 °C and pH 10. The Michaelis-Menten kinetic behavior of pectinase was slightly changed after immobilization and immobilized pectinase showed somewhat higher K_m and lower V_max value as compared to soluble pectinase. Polyacrylamide gel encapsulation enhanced the thermal stability of pectinase and encapsulated pectinase showed higher thermal stability against various temperature ranging from ranging from 30 °C to 50 °C as compared free pectinase. Furthermore, the surface topography of polyacrylamide gel was analyzed using scanning electron microscopy and it was observed that the surface topography of polyacrylamide gel was changed after encapsulation. The encapsulation of pectinase within polyacrylamide gel enhanced the possibility of reutilization of pectinase in various industries and pectinase retained more than 50% of its initial activity even after seven batch of reactions.

A novel peroxidase from runner bean (Phaseolus coccineus L.): Enhanced affinity purification, characterization, and dye decolorization activity

In this study, a novel runner bean peroxidase (RBP) was purified and characterized. Affinity-based purification was performed with newly synthesized disubstituted 4-aminobenzohydrazides. In the purification results, 253-fold was achieved with a yield of 56.2%. Furthermore, molecular weight and enzyme purity were checked with the SDS-PAGE and observed a single band at 31.2 kDa. Optimum conditions were determined as temperature = 50°C, ionic strength = 0.2 M, and pH 7.0. Enzyme exhibited 31.2% of residual activity in the presence of 20% DMSO. Additionally, the redox-mediated decolorization effect of the enzyme was examined for Reactive Blue 19 and Acid Blue 25 dyes. As a result of 1-hr incubation, the enzyme removal activity of Reactive Blue 19 and Acid Blue 25 dyes was calculated as 47% and 57%, respectively. PRACTICAL APPLICATIONS: Peroxidases (PODs) ability to catalyze various redox reactions for many substrates makes them significant enzymes in industrial sectors. In our current report, a single-step strategy was developed and followed as an alternative to multi-step methods commonly used for the purification of PODs. During this process, high yield was achieved and the separation time was shortened. Also, the purification of RBP that can potentially supplant PODs used in the industrial applications was carried out for the first time. In addition, substrate specificity, catalytic behavior in water-miscible organic solvents, and dye bleaching activity of this enzyme have been determined to evaluate the utilization capacity in various processes.

Immobilization of Peroxidase on Functionalized MWCNTs-Buckypaper/Polyvinyl alcohol Nanocomposite Membrane

Surface modified Multi-walled carbon nanotubes (MWCNTs) Buckypaper/Polyvinyl Alcohol (BP/PVA) composite membrane was synthesized and utilized as support material for immobilization of Jicama peroxidase (JP). JP was successfully immobilized on the BP/PVA membrane via covalent bonding by using glutaraldehyde. The immobilization efficiency was optimized using response surface methodology (RSM) with the face-centered central composite design (FCCCD) model. The optimum enzyme immobilization efficiency was achieved at pH 6, with initial enzyme loading of 0.13 U/mL and immobilization time of 130 min. The results of BP/PVA membrane showed excellent performance in immobilization of JP with high enzyme loading of 217 mg/g and immobilization efficiency of 81.74%. The immobilized system exhibited significantly improved operational stability under various parameters, such as pH, temperature, thermal and storage stabilities when compared with free enzyme. The effective binding of peroxidase on the surface of the BP/PVA membrane was evaluated and confirmed by Field emission scanning electron microscopy (FESEM) coupled with Energy Dispersive X-Ray Spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR) and Thermogravimetric Analysis (TGA). This work reports the characterization results and performances of the surface modified BP/PVA membrane for peroxidase immobilization. The superior properties of JP-immobilized BP/PVA membrane make it promising new-generation nanomaterials for industrial applications.

Continuous degradation of Direct Red 23 by calcium pectate-bound Ziziphus mauritiana peroxidase: identification of metabolites and degradation routes

In the present study, oxido-reductive degradation of diazo dye, Direct Red 23, has been carried out by Ziziphus mauritiana peroxidases (specific activity 17.6 U mg^-1). Peroxidases have been immobilized via simple adsorption and cross-linking by glutaraldehyde; adsorbed and cross-linked enzyme retained 94.28% and 91.23% of original activity, respectively. The stability of peroxidases was enhanced significantly upon immobilization; a marked widening in both pH and temperature activity profiles were observed. Adsorbed peroxidases exhibited similar pH and temperature optima as reported for the free enzyme. Thermal stability was significantly enhanced in case of cross-linked enzyme which showed 80.52% activity even after 2 h of incubation at 60 °C. Packed bed reactors containing adsorbed and cross-linked peroxidases were run over a period of 4 weeks; adsorbed peroxidases retained 52.86% activity whereas cross-linked peroxidases maintained over 77% dye decolorization ability at the end of the fourth week of its continuous operation. Gas chromatography coupled with mass spectrometry was used to analyze the degradation products; it showed the presence of four major metabolites. Degradation of dye starts with the 1-Hydroxybenzotriazole radical attack on the carbon atom of the phenolic ring bearing azo linkage, converting it into cation radical which underwent nucleophilic attack by a water molecule and results in cleavage of chromophore via symmetric and asymmetric cleavage pathways. Intermediates undergo spontaneous removal of nitrogen, deamination, and oxidation reactions to produce maleic acid as the final degradation product. Graphical abstract.

Laccase immobilization on the electrode surface to design a biosensor for the detection of phenolic compound such as catechol

Biosensors based on the coupling of a biological entity with a suitable transducer offer an effective route to detect phenolic compounds. Phenol and phenolic compounds are among the most toxic environmental pollutants. Laccases are multi-copper oxidases that can oxide phenol and phenolic compounds. A method is described for construction of an electrochemical biosensor to detect phenolic compounds based on covalent immobilization of laccase (Lac) onto polyaniline (PANI) electrodeposited onto a glassy carbon (GC) electrode via glutaraldehyde coupling. The modified electrode was characterized by voltammetry, Fourier transform infrared (FTIR) spectroscopy and atomic force microscopy (AFM) techniques. The results indicated that laccase was immobilized onto modified GC electrode by the covalent interaction between laccase and terminal functional groups of the glutaraldehyde. The laccase immobilized modified electrode showed a direct electron transfer reaction between laccase and the electrode. Linear range, sensitivity, and detection limit for this biosensor were 3.2 × 10(-6) to 19.6 × 10(-6)M, 706.7 mAL mol(-1), 2.07 × 10(-6)M, respectively.

An updated view on horseradish peroxidases: recombinant production and biotechnological applications

Horseradish peroxidase has been the subject of scientific research for centuries. It has been used exhaustively as reporter enzyme in diagnostics and histochemistry and still plays a major role in these applications. Numerous studies have been conducted on the role of horseradish peroxidase in the plant and its catalytic mechanism. However, little progress has been made in its recombinant production. Until now, commercial preparations of horseradish peroxidase are still isolated from plant roots. These preparations are commonly mixtures of various isoenzymes of which only a small fraction has been described so far. The composition of isoenzymes in these mixed isolates is subjected to uncontrollable environmental conditions. Nowadays, horseradish peroxidase regains interest due to its broad applicability in the fields of medicine, life sciences, and biotechnology in cancer therapy, biosensor systems, bioremediation, and biocatalysis. These medically and commercially relevant applications, the recent discovery of new natural isoenzymes with different biochemical properties, as well as the challenges in recombinant production render this enzyme particularly interesting for future biotechnological solutions. Therefore, we reviewed previous studies as well as current developments with biotechnological emphasis on new applications and the major remaining biotechnological challenge—the efficient recombinant production of horseradish peroxidase enzymes.

Activity and stability of urease entrapped in thermosensitive poly(N-isopropylacrylamide-co-poly(ethyleneglycol)-methacrylate) hydrogel

Urease was entrapped in thermally responsive poly(N-isopropylacrylamide-co-poly(ethyleneglycol)-methacrylate), p[NIPAM-p(PEG)-MA], copolymer hydrogels. The copolymer membrane shows temperature-responsive properties similar to conventional p(NIPAM) hydrogels, which reversibly swell below and de-swell above the lower critical solution temperature of p(NIPAM) hydrogel at around 32 °C. The retained activities of the entrapped urease (in p[NIPAM-p(PEG)-MA]-4 hydrogels) were between 83 and 53% compared to that of the same quantity of free enzyme. Due to the thermo-responsive character of the hydrogel matrix, the maximum activity was achieved at around 25 °C with the immobilized urease. Optimum pH was the same for both free and entrapped enzyme. Operational, thermal and storage stabilities of the enzyme were found to increase with entrapment of urease in the thermoresponsive hydrogel matrixes. As for reusability, the immobilized urease retained 89% of its activity after ten repeated uses.

Immobilization of tyrosinase on modified diatom biosilica: enzymatic removal of phenolic compounds from aqueous solution

Acid and plasma treated diatom-biosilica particles, were modified with 3-aminopropyl triethoxysilane (APTES), and activated with glutaraldehyde. Then, tyrosinase was immobilized onto the pre-activated biosilica by covalent bonding. The biosilica properties were determined using SEM, and FTIR. The enzyme system has been characterized as a function of pH, temperature and substrate concentration. Optimum pH of the free and immobilized enzyme was found to be pH 7.0. Optimum temperatures of the free and immobilized enzymes were determined as 35 and 45 °C respectively. The biodegradation of phenolic compounds (i.e., phenol, para-cresol and phenyl acetate) has been studied by means of immobilized tyrosinase in a batch system. The immobilized tyrosinase retained about 74% of its original activity after 10 times repeated use in the batch system. Moreover, the storage stability of the tyrosinase-biosilica system resulted excellent, since they maintained more than 67% of the initial activity after eighth week storage. Highly porous structure of biosilica can provide large surface area for immobilization of high quantity enzyme. The porous structure of the biosilica can decrease diffusion limitation both substrate phenols and their products. Finally, the immobilized tyrosinase was used in a batch system for degradation of three different phenols.