Covalent immobilization of organophosphorus hydrolase enzyme on chemically modified cellulose microfibers: Statistical optimization and characterization

Enhanced performance of bacterial laccase via microbial surface display and biomineralization for portable detection of phenolic pollutants

Designing a portable device based on bacterial laccase (BLac) for on-site assay of phenolic contaminants presents significant challenges. Here, we achieved comprehensive performance enhancement of BLac by integrating biomineralization and microbial surface display technologies. The introduction of cell surface-displayed bacterial laccase (CSD-BLac) reduced costs and improved sensitivity compared to detection methods based on free Blac and whole-cell catalyst. Further, the biomineralization dramatically enhanced the catalytic efficiency (Vmax/Km) of mineralized CSD-BLac (M-CSD-BLac), making it 1.98 times higher than that of CSD-BLac. Mineralization conditions could significantly affect the activity of M-CSD-Blac. Moreover, the biomineralization layer also enhanced the resistance of M-CSD-BLac against high temperature, metal ions, ionic strength and storage time. Further, a portable assay device was developed for detection of phenolic pollutants by depositing M-CSD-BLac on a syringe filter membrane, which demonstrated easy operation, rapid detection (10 min), good reusability (20 cycles). The device not only could reliably differentiate three types of phenols but also quantitatively detect them with high sensitivity. For phenol, m-aminophenol, and p-nitrophenol, the limits of detection were 0.09, 0.28 and 0.17 μM, with detection ranges of 10-70, 20-80 and 15-110 μM, respectively. Additionally, the porous structure of M-CSD-BLac layer and the insertion of M-CSD-BLac into the filter membrane pores allowed effective filtration of smaller pigments from real samples, eliminating the need for additional pretreatment. This work not only proposes a strategy for elevating the activity and stability of laccase, but also stimulates the development of portable assay devices for on-site environmental monitoring.

SUMO-G5C23-D208G@ZIF-F: A Novel Immobilized Enzyme with Enhanced Stability and Reusability for Organophosphorus Hydrolysis

Organophosphorus hydrolase (OPH) is a highly effective bioscavenger for detoxifying hazardous organophosphorus compounds. However, its practical application is hindered by low yield and poor stability. In this study, we employed Small Ubiquitin-like Modifier (SUMO) fusion expression to enhance the solubility of the OPH mutant G5C23-D208G and, for the first time, immobilized the enzyme on a zeolitic imidazolate framework-F (ZIF-F) carrier to improve its stability. The SUMO-G5C23-D208G fusion protein was successfully expressed in Escherichia coli, resulting in a yield that was 2.4 times higher than that of native OPH and an 11-fold increase in solubility. The purified protein achieved a purity of 95%. The immobilized enzyme, SU-MO-G5C23-D208G@ZIF-F, exhibited a farfalle-shaped structure with a diameter of approximately 3-5 μm. Compared to the free enzyme, the immobilized enzyme maintained high catalytic efficiency (kcat/Km = 8.9 × 104 M-1·s-1) and demonstrated enhanced thermal stability, pH stability, and reusability. This study has significantly improved the yield and stability of OPH, thereby supporting its potential for industrial applications.

Grafting of proteins onto polymeric surfaces: A synthesis and characterization challenge

This review aims at answering the following question: how can a researcher be sure to succeed in grafting a protein onto a polymer surface? Even if protein immobilization on solid supports has been used industrially for a long time, hence enabling natural enzymes to serve as a powerful tool, emergence of new supports such as polymeric surfaces for the development of so-called intelligent materials requires new approaches. In this review, we introduce the challenges in grafting protein on synthetic polymers, mainly because compared to hard surfaces, polymers may be sensitive to various aqueous media, depending on the pH or reductive molecules, or may exhibit state transitions with temperature. Then, the specificity of grafting on synthetic polymers due to difference of chemical functions availability or difference of physical properties are summarized. We present next the various available routes to covalently bond the protein onto the polymeric substrates considering the functional groups coming from the monomers used during polymerization reaction or post-modification of the surfaces. We also focus our review on a major concern of grafting protein, which is avoiding the potential loss of function of the immobilized protein. Meanwhile, this review considers the different methods of characterization used to determine the grafting efficiency but also the behavior of enzymes once grafted. We finally dedicate the last part of this review to industrial application and future prospective, considering the sustainable processes based on green chemistry.

Effective immobilization of lactate dehydrogenase onto mesoporous silica

This study presents that covalent immobilization technique has been utilized for the immobilization of l-lactate dehydrogenase (l-LDH) from porcine on mesoporous silica. To develop mesoporous silica as support material for use in l-LDH immobilization, the particle surfaces were functionalized with 3-aminopropyltrimethoxysilane and further conjugated with glutaraldehyde. The effect of some parameters such as glutaraldehyde concentration, immobilization pH, initial enzyme concentration, and immobilization time was investigated and the optimum conditions for these parameters were determined as 1% (w/v), pH 8.0, 1 mg/ml, and 120 min, respectively. The maximum working pH and temperature for the oxidation of lactate to pyruvate reaction were determined as 10.0 and 35°C for free and 9.0 and 40°C for immobilized l-LDH, respectively. The kinetic parameters (K_m and V_max ) of l-LDH for the oxidation of lactate to pyruvate reaction were examined as 1.02 mM and 7.58 U/mg protein for free and 0.635 mM and 1.7 U/mg protein for immobilized l-LDH, respectively. Moreover, the immobilized l-LDH was 1.3-fold more stable than free l-LDH at 25°C according to calculated t_1/2 values. The immobilized l-LDH retained 80% of its initial activity in a batch reactor after 14 reuses.

The evaluation of the performance of rice husk and rice straw as potential matrix to obtain the best lipase immobilized system: creating wealth from wastes

India generates 126.6 and 42 million tons of Rice straw (RS) and Rice husk (RH) annually, respectively. These agro-processing wastes feedstock are dumped in landfills or burnt, releasing toxic gases and particulate matter into the environment. This paper explores the valorization of these wastes feedstock into sustainable, economic products. We compare these wastes as matrices for lipase immobilization. These matrices were characterized, different parameters (pH, temperature, ionic strength, and metal ion cofactors) were checked, and the selected matrix was analyzed for reusability and hydrolysis of vegetable oils. Lipase immobilized Rice straw (LIRS) showed the highest activity with 72.84% protein loading. Field emission scanning electron microscopy (FESEM) demonstrated morphological changes after enzyme immobilization. FTIR showed no new bond formation, and immobilization data was fitted to Freundlich adsorption isotherm (with K = 12.18 mg/g, n_F = 4.5). The highest activity with protein loading, 91.05%, was observed at pH 8, 37 °C temperature, 50 mM ionic strength, and lipase activity doubled in the presence of Mg²⁺ ions. The LIRS retained 75% of its initial activity up to five cycles and efficiently hydrolyzed different oils. The results reflected that the LIRS system performs better and can be used to degrade oily waste.

Overview of a bioremediation tool: organophosphorus hydrolase and its significant application in the food, environmental, and therapy fields

In the past decades, the organophosphorus compounds had been widely used in the environment and food industries as pesticides. Owing to the life-threatening and long-lasting problems of organophosphorus insecticide (OPs), an effective detection and removal of OPs have garnered growing attention both in the scientific and practical fields in recent years. Bacterial organophosphorus hydrolases (OPHs) have been extensively studied due to their high specific activity against OPs. OPH could efficiently hydrolyze a broad range of substrates both including the OP pesticides and some nerve agents, suggesting a great potential for the remediation of OPs. In this review, the microbial identification, molecular modification, and practical application of OPHs were comprehensively discussed.Key points• Microbial OPH is a significant bioremediation tool against OPs.• Identification and molecular modification of OPH was discussed in detail.• The applications of OPH in food, environmental, and therapy fields are presented.

Preparation of efficient, stable, and reusable copper-phosphotriesterase hybrid nanoflowers for biodegradation of organophosphorus pesticides

Phosphotriesterase (PTE) is considered to be a good biodegradation agent for organophosphorus pesticides. However, the instability of the free PTE limits its application. In this study, the free PTE was hybridized with copper ions (Cu²⁺) to enhance its catalytic stability and activity. The acquired particles were freeze-dried after precipitation with PO₄^3- at 4 °C for 72 h. Scanning electron microscopy showed that the Cu-PTE complexes formed flower-like nanoparticles after hybridization. The characteristic peaks of both the enzyme and metal material were revealed by Fourier transform-infrared spectroscopy. X-ray diffraction analysis indicated that PTE was encapsulated in the Cu₃(PO₄)₂·3H₂O based hybrid nanoflowers. Compared with free PTE, the catalytic activity of Cu-PTE hybrid nanoflowers was significantly increased about 2.2 fold. The catalytic efficiency (k_cat/V_max) of Cu-PTE hybrid nanoflowers was 1.76 fold than that of free PTE. The stability of the immobilized PTE under thermal and pH conditions was improved and the tolerance of it to organic solvents was also enhanced. Moreover, the Cu-PTE hybrid nanoflowers still exhibited 72.3 % relative activity after ten consecutive reactions. In general, this is the first time to use copper based hybrid nanoflowers to immobilize PTE, and the immobilized enzyme shows excellent performance on OPs degradation. The Cu-PTE hybrid nanoflowers may have great potential in the biodegradation of organophosphorus compounds in future.

Enhancing organophosphate hydrolase efficacy via protein engineering and immobilization strategies

Organophosphorus compounds (OPs), developed as pesticides and chemical warfare agents, are extremely toxic chemicals that pose a public health risk. Of the different detoxification strategies, organophosphate-hydrolyzing enzymes have attracted much attention, providing a potential route for detoxifying those exposed to OPs. Phosphotriesterase (PTE), also known as organophosphate hydrolase (OPH), is one such enzyme that has been extensively studied as a catalytic bioscavenger. In this review, we will discuss the protein engineering of PTE aimed toward improving the activity and stability of the enzyme. In order to make enzyme utilization in OP detoxification more favorable, enzyme immobilization provides an effective means to increase enzyme activity and stability. Here, we present several such strategies that enhance the storage and operational stability of PTE/OPH.

Improving activity and stabilization of urease by crosslinking to nanoaggregate forms for herbicide degradation

Bioremediation is the most effective green protocol for degradation of environmental contaminants. Present study involves carrier free urease immobilization with synthesis of its new crosslinked aggregates using two different crosslinkers, divinyl benzene (DVB) and tripropyleneglycol dimethacrylate (TPGDA) via free radical mechanism. Resulting crosslinked ureases were further converted to nanoform (CLUNAs) using solvent evaporation technique. The activity of free and the crosslinked ureases was studied as a function of operational parameters viz. temperature (20-80), pH (2-11) and substrate concentration (5-20 mM) using urea as substrate at contact time of 10 min. Storability study of the pristine urease and CLUNAs was carried out for 40 days, and the CLUNAs were reused in 10 repeat cycles to assess their reusability. Isoproturone degradation was studied under the above-cited range of pH and temperature and results were recorded after 24 h.

Novel approach using activated cellulose film for efficient immobilization of purified diamine oxidase to enhance enzyme performance and stability

The presence of various contaminants in foodstuffs has led to serious public health concerns. Diamine oxidase (DAO) has attracted tremendous attention for guarding food safety as well as clinical and environmental industries. In this study, DAO from Pisum sativum (Pea) seedlings was extracted and purified by dialysis and gel filtration. Purified DAO was covalently immobilized onto the surface of nitrocellulose membrane using glutaraldehyde. The obtained bioaffinity support has efficiently shown high yield immobilization of DAO from pea seedlings. The optimal conditions of free and immobilized DAO activity were evaluated against the substrate, Putrescine dihydrochloride. The influence of pH, temperature, storage stability, and reusability of immobilized enzyme with comparison to the free enzyme was studied and the results showed that the stabilities were significantly enhanced compared with free counterpart. Residual activity of the immobilized enzyme was 59% of the initial activity after being recycled 10 times. We approve that this novel low cost immobilized DAO carrier presents a new approach in large scale applications.

Organophosphorus hydrolase-poly-β-cyclodextrin as a stable self-decontaminating bio-catalytic material for sorption and degradation of organophosphate pesticide

A region suffering from an attack of a nerve agent requires not only a highly sorptive material but also a fast-acting catalyst to decontaminate the lethal chemical present. The product should be capable of high sorptive capacity, selectivity and quick response time to neutralize the long lasting harmful effects of nerve agents. Herein, we have utilized organophosphorus hydrolase (OPH) as a non-toxic bio-catalytic material held in with the supporting matrix of poly-β-cyclodextrin (PCD) as a novel sorptive reinforced self-decontaminating material against organophosphate intoxication. OPH coated PCD (OPH-PCD) will not only be providing support for holding enzyme but also would be adsorbing methyl paraoxon (MPO) used as a simulant, in a host-guest inclusion complex formation. Sorption trend for PCD revealed preference towards the more hydrophobic MPO against para-nitrophenol (pNP). The results show sorption capacity of 1.26 mg/g of 100 μM MPO with PCD which was 1.7 times higher compared to pNP. The reaction rate with immobilized OPH-PCD was found to be 23% less compared to free enzyme. With the help of OPH-PCD, continuous hydrolysis (100%) of MPO into pNP was observed for a period of 24 h through packed bed reactor with good reproducibility and stability of enzyme. The long-term stability also confirmed its stable nature for the investigation period of 4 days where it maintained activity. Combined with its fast and reactive nature, the resulting self-decontaminating regenerating material provides a promising strategy for the neutralization of nerve agents and preserving the environment.

Cellulose-Supported Ionic Liquid Phase Catalyst-Mediated Mannich Reaction

Cellulose-supported ionic liquid phase (SILP) catalyst containing a camphor sulfonate anion with a pendant ferrocenyl group was prepared and characterised with different analytical techniques such as Fourier-transform infrared, Fourier-transform Raman, and cross polarization–magic angle spinning (CP-MAS) 13C NMR spectroscopy, X-ray diffraction, scanning electron microscopy, and thermogravimetric analysis. The SILP catalyst displayed excellent catalytic activity in the synthesis of β-amino carbonyl compounds by Mannich reaction. Recycling studies revealed that SILP catalyst could be reused six times without significant decrease in catalytic activity.