Remarkably enhanced activity and substrate affinity of lipase covalently bonded on zwitterionic polymer-grafted silica nanoparticles

Exploring the impact of silver-based nanomaterial feed additives on green algae through single-cell techniques

Silver in its various forms, including dissolved silver ions (Ag+) and silver nanoparticles (AgNPs), is a promising alternative to traditional antibiotics, largely used in livestock as feed additives and could contribute to the decrease and avoidance of the development of antibiotic resistance. The present study aims to assess the potential ecotoxicity of a silver-based nanomaterial (Ag-kaolin), the feed supplemented with the nanomaterial and the faeces since the latter are the ones that finally reach the environment. To this end, green alga Raphidocellis subcapitata was exposed to the extracts of Ag-kaolin, supplemented feed, and pig faeces for 72 h, along with Ag+ and AgNPs as controls for comparison purposes. Given the complexity of the studied materials, single-cell techniques were used to follow the changes in the cell numbers and chlorophyll fluorescence by flow cytometry, and the accumulation of silver in the exposed cells by single cell inductively coupled plasma mass spectrometry (SC-ICP-MS). Changes in cell morphology were observed by cell imaging multimode reader. The results revealed a decrease in chlorophyll fluorescence, even at low concentrations of Ag-kaolin (10 μg L-1) after 48 h of exposure. Additionally, complete growth inhibition was found with this material like the results obtained by exposure to Ag+. For the supplemented feed, a concentration of 50 μg L-1 was necessary to achieve complete growth inhibition. However, the behaviour differed for the leachate of faeces, which released Ag2S and AgCl alongside Ag+ and AgNPs. At 50 μg L-1, inhibition was minimal, primarily due to the predominance of less toxic Ag2S in the leachate. The uptake of silver by the cells was confirmed with all the samples through SC-ICP-MS analysis. These findings demonstrate that the use of Ag-kaolin as a feed supplement will lead to a low environmental impact.

Enhanced Enzymatic Performance of Immobilized Pseudomonas fluorescens Lipase on ZIF-8@ZIF-67 and Its Application to the Synthesis of Neryl Acetate with Transesterification Reaction

In this study, hybrid skeleton material ZIF-8@ZIF-67 was synthesized by the epitaxial growth method and then was utilized as a carrier for encapsulating Pseudomonas fluorescens lipase (PFL) through the co-precipitation method, resulting in the preparation of immobilized lipase (PFL@ZIF-8@ZIF-67). Subsequently, it was further treated with glutaraldehyde to improve protein immobilization yield. Under optimal immobilization conditions, the specific hydrolytic activity of PFL@ZIF-8@ZIF-67 was 20.4 times higher than that of the free PFL. The prepared biocatalyst was characterized and analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared (FT-IR). Additionally, the thermal stability of PFL@ZIF-8@ZIF-67 at 50 °C was significantly improved compared to the free PFL. After 7 weeks at room temperature, PFL@ZIF-8@ZIF-67 retained 78% of the transesterification activity, while the free enzyme was only 29%. Finally, PFL@ZIF-8@ZIF-67 was applied to the neryl acetate preparation in a solvent-free system, and the yield of neryl acetate reached 99% after 3 h of reaction. After 10 repetitions, the yields of neryl acetate catalyzed by PFL@ZIF-8@ZIF-67 and the free PFL were 80% and 43%, respectively.

Electrostatically Mediated In Situ Polymerization for Enzyme Immobilization and Activation

Enzyme immobilization in nanoparticles is of interest for boosting their catalytic applications, yet rational approaches to designs achieving both high enzyme loading and activation remain a challenge. Herein, we report an electrostatically mediated in situ polymerization strategy that simultaneously realizes enzyme immobilization and activation. This was achieved by copolymerizing cationic monomers with a cross-linker in the presence of the enzyme lipase (anionic) as the template, which produces enzyme-loaded nanogels. The effects of different control factors such as pH, lipase dosage, and cross-linker fraction on nanogel formation are investigated systematically, and optimal conditions for enzyme loading and activation have been determined. A central finding is that the cationic polymer network of the nanogel creates a favorable environment that not only protects the enzyme but also boosts enzymatic activity nearly 2-fold as compared to free lipase. The nanogels improve the stability of the lipase to tolerate a broader working range of pH (5.5-8.5) and temperature (25-70 °C) and allow recycling such that after six cycles of reaction, 70% of the initial activity is conserved. The established fabrication strategy can be applied generally to different cationic monomers, and most of these nanogels exhibit adequate immobilization and activation of lipase. Our study confirms that in situ polymerization based on electrostatic interaction provides a facile and robust strategy for enzyme immobilization and activation. The wide variety of ionic monomers, therefore, features great potential for developing functional platforms toward satisfying enzyme immobilization and demanding applications.

Cationic Polymers Remarkably Boost Haloalkane Dehalogenase Activity in Organic Solvent Solutions and the Molecular Implications

Applications of haloalkane dehalogenase DhaA in biocatalysis are limited by its unfavorable performance in organic solvents. Our previous work proved that mutations of surface positive-charged residues enhanced the organic solvent resistance of DhaA, which inspired us to explore the effect of cationic polymers on DhaA in organic solvents. Remarkably boosted performance was achieved in different organic solvent solutions by introducing cationic polymers, for example, there was a 6.1-fold activity increase with poly(allylamine hydrochloride) and a 5.5-fold activity increase with poly(ethylene imine) in 40 vol.% dimethylsulfoxide. The presence of cationic polymers protected DhaA from damage by organic solvents and increased the substrate concentration around the enzyme-polymer complex. Fluorescence spectroscopy and molecular dynamics simulations revealed that the binding of cationic polymers onto DhaA weakened the interactions between organic solvents and DhaA, decreased the organic solvent solvation level around DhaA, and enhanced the structural stability of DhaA in organic solvents. This comprehensive understanding of the effect of cationic polymers on DhaA can help to broaden the applications of DhaA in organic solvent-involved biocatalysis.

Trends in the Use of Lipases: A Systematic Review and Bibliometric Analysis

Scientific mapping using bibliometric data network analysis was applied to analyze research works related to lipases and their industrial applications, evaluating the current state of research, challenges, and opportunities in the use of these biocatalysts, based on the evaluation of a large number of publications on the topic, allowing a comprehensive systematic data analysis, which had not yet been conducted in relation to studies specifically covering lipases and their industrial applications. Thus, studies involving lipase enzymes published from 2018 to 2022 were accessed from the Web of Science database. The extracted records result in the analysis of terms of bibliographic compatibility among the articles, co-occurrence of keywords, and co-citation of journals using the VOSviewer algorithm in the construction of bibliometric maps. This systematic review analysis of 357 documents, including original and review articles, revealed studies inspired by lipase enzymes in the research period, showing that the development of research, together with different areas of knowledge, presents good results related to the applications of lipases, due to information synchronization. Furthermore, this review showed the main challenges in lipase applications regarding increased production and operational stability; establishing well-defined evaluation criteria, such as cultivation conditions, activity, biocatalyst stability, type of support and reactor; thermodynamic studies; reuse cycles; and it can assist in defining goals for the development of successful large-scale applications, showing several points for improvement of future studies on lipase enzymes.

Reshaping the Binding Pocket of Cellobiose 2-Epimerase for Improved Substrate Affinity and Isomerization Activity for Enabling Green Synthesis of Lactulose

Enzymatic isomerization of lactose into lactulose via cellobiose 2-epimerase (CE) could provide an eco-friendly route for the industrial production of lactulose, a valuable food prebiotic. However, poor substrate affinity for lactose and preference for epimerization over isomerization hinder this application. Previous studies on CE improvement have focused on random mutagenesis or active site rational design; little is known about the relationship between substrate binding and enzyme efficacy, which was hence the subject of this study. First, residues 372W and 308W were identified as key for disaccharide recognition in CEs based on crystal structure alignment of the N-acetyl-glucosamine 2-epimerase superfamily and site-directed mutation. This binding domain was then reshaped through site saturation mutagenesis, resulting in seven mutants with enhanced isomerization activity. The optimal mutant CsCE/Q371E had significantly enhanced substrate affinity (K_m, 269.65 mM vs K_m, 417.5 mM), reduced epimerization activity, and 3.3-fold increased isomerization activity over the original CsCE. Molecular dynamics simulation further revealed that substituting Gln-371 with Glu strengthened the hydrogen-bonding network and altered the active site-substrate interactions, increasing the substrate stability and shifting the catalytic direction. This study uncovered new information about the substrate binding region and its mechanisms and impact on CE catalytic performance, paving the way for potential commercial applications.

Silica nanoparticles: Biomedical applications and toxicity

Silica nanoparticles (SiNPs) are composed of silicon dioxide, the most abundant compound on Earth, and are used widely in many applications including the food industry, synthetic processes, medical diagnosis, and drug delivery due to their controllable particle size, large surface area, and great biocompatibility. Building on basic synthetic methods, convenient and economical strategies have been developed for the synthesis of SiNPs. Numerous studies have assessed the biomedical applications of SiNPs, including the surface and structural modification of SiNPs to target various cancers and diagnose diseases. However, studies on the in vitro and in vivo toxicity of SiNPs remain in the exploratory stage, and the toxicity mechanisms of SiNPs are poorly understood. This review covers recent studies on the biomedical applications of SiNPs, including their uses in drug delivery systems to diagnose and treat various diseases in the human body. SiNP toxicity is discussed in terms of the different systems of the human body and the individual organs in those systems. This comprehensive review includes both fundamental discoveries and exploratory progress in SiNP research that may lead to practical developments in the future.

Mechano-chemical and biological energetics of immobilized enzymes onto functionalized polymers and their applications

Enzymes of commercial importance, such as lipase, amylase, laccase, phytase, carbonic anhydrase, pectinase, maltase, glucose oxidase etc., show multifunctional features and have been extensively used in several fields including fine chemicals, environmental, pharmaceutical, cosmetics, energy, food industry, agriculture and nutraceutical etc. The deployment of biocatalyst in harsh industrial conditions has some limitations, such as poor stability. These drawbacks can be overcome by immobilizing the enzyme in order to boost the operational stability, catalytic activity along with facilitating the reuse of biocatalyst. Nowadays, functionalized polymers and composites have gained increasing attention as an innovative material for immobilizing the industrially important enzyme. The different types of polymeric materials and composites are pectin, agarose, cellulose, nanofibers, gelatin, and chitosan. The functionalization of these materials enhances the loading capacity of the enzyme by providing more functional groups to the polymeric material and hence enhancing the enzyme immobilization efficiency. However, appropriate coordination among the functionalized polymeric materials and enzymes of interest plays an important role in producing emerging biocatalysts with improved properties. The optimal coordination at a biological, physical, and chemical level is requisite to develop an industrial biocatalyst. Bio-catalysis has become vital aspect in pharmaceutical and chemical industries for synthesis of value-added chemicals. The present review describes the current advances in enzyme immobilization on functionalized polymers and composites. Furthermore, the applications of immobilized enzymes in various sectors including bioremediation, biosensor and biodiesel are also discussed.

Surfaces with Antifouling-Antimicrobial Dual Function via Immobilization of Lysozyme on Zwitterionic Polymer Thin Films

Due to the emergence of wide-spread infectious diseases, there is a heightened need for antimicrobial and/or antifouling coatings that can be used to prevent infection and transmission in a variety...

Enhanced enzymatic performance of immobilized lipase on metal organic frameworks with superhydrophobic coating for biodiesel production

Inspired by the interfacial catalysis of lipase, Herein, the hydrophobic ZIF-L coated with polydimethylsiloxane (PDMS) were prepared by chemical vapor deposition (CVD) and used to immobilize lipase from Aspergillus oryzae (AOL) for biodiesel production. The results showed that the PDMS coating enhanced the stability of ZIF-8 and ZIF-L in PBS. Immobilization efficiency of AOL on PDMS-modified ZIF-L was 96% under optimized conditions. The resultant immobilized lipase (AOL@PDMS-ZIF-L) exhibited higher activity recovery (430%) than AOL@ZIF-L. Meanwhile, compared with free lipase, the AOL@PDMS-ZIF-L exhibited better storage stability and thermal stability. After 150 days of storage, the free lipase retained only 20% of its original activity of hydrolyzing p-NPP, while the AOL@PDMS-ZIF-L still retained 90% of its original activity. The biodiesel yield catalyzed from soybean oil by free lipase was only 69%, However, the biodiesel yield by AOL@PDMS-ZIF-L reached 94%, and could still be maintained at 85% even after 5 consecutive cycles. It is believed that this convenient and versatile strategy has great promise in the important fields of immobilized lipase on MOF for biodiesel production.

Improved catalytic performance of carrier-free immobilized lipase by advanced cross-linked enzyme aggregates technology

The cross-linked enzyme aggregates (CLEAs) are one of the technologies that quickly immobilize the enzyme without a carrier. In this study, ionic liquid with amino group (1-aminopropyl-3-methylimidazole bromide, FIL) was used as the novel functional surface molecule to modify CRL (Candida rugosa lipase, CRL). The enzymatic properties of CRL-FIL-CLEAs were investigated. The activity of CRL-FIL-CLEAs (5.51 U/mg protein) was 1.9 times higher than that of CRL-CLEAs (2.86 U/mg protein) without surface modification. After incubating in a centrifuge tube for 50 min at 60 °C, CRL-FIL-CLEAs still maintained 61% of its initial activity, while the value for CRL-CLEAs was only 22%. After repeated use for five times, compared with the 22% residual activity of CRL-CLEAs, the value of CRL-FIL-CLEAs was 51%. Based on the above results, it was indicated that this method provided a new idea for the effective synthesis of immobilized enzyme.

Temperature-resistant and solvent-tolerant lipases as industrial biocatalysts: Biotechnological approaches and applications

The development of new biocatalytic systems to replace the chemical catalysts, with suitable characteristics in terms of efficiency, stability under high temperature reactions and in the presence of organic solvents, reusability, and eco-friendliness is considered a very important step to move towards the green processes. From this basis, the use of lipase as a catalyst is highly desired for many industrial applications because it offers the reactions in which could be used, stability in harsh conditions, reusability and a greener process. Therefore, the introduction of temperature-resistant and solvent-tolerant lipases have become essential and ideal for industrial applications. Temperature-resistant and solvent-tolerant lipases have been involved in many large-scale applications including biodiesel, detergent, food, pharmaceutical, organic synthesis, biosensing, pulp and paper, textile, animal feed, cosmetics, and leather industry. So, the present review provides a comprehensive overview of the industrial use of lipase. Moreover, special interest in biotechnological and biochemical techniques for enhancing temperature-resistance and solvent-tolerance of lipases to be suitable for the industrial uses.

Enhancing bio-catalytic performance of lipase immobilized on ionic liquids modified magnetic polydopamine

In this study, imidazolium-based ionic liquid with [tf₂N]^- as the anion was successfully grafted to magnetic polydopamine nanoparticles (MPDA). The prepared materials were well characterized and used as supports for lipase immobilization. The immobilized lipase (PPL-ILs-MPDA) exhibited excellent activity and stability. The specific activity of PPL-ILs-MPDA was 2.15 and 1.49 folds higher than that of free PPL and PPL-MPDA. In addition, after 10 rounds of reuse, the residual activity of PPL-ILs-MPDA was 86.2 % higher than that of PPL-MPDA (75.4 %). Furthermore, the kinetic assay indicated that the affinity between PPL-ILs-MPDA and substrate had increased. Analysis of the secondary structure using circular dichroism was used to explain the mechanism underlying the improvement in the performance of PPL-ILs-MPDA. In addition, the immobilized lipase can be easily separated from the reaction system with a magnet. The observations regarding the development of new supports for lipase immobilization may provide new ideas regarding further studies in this field.

Immobilization of lipase on the modified magnetic diatomite earth for effective methyl esterification of isoamyl alcohol to synthesize banana flavor

The present study was designed to propose a simple, cost-effective, and efficient method for the preparation of a biocompatible composite made from magnetic diatomaceous earth (mDE) coated by aminopropyltriethoxysilane (APTES) and its application for immobilization of porcine pancreatic lipase (PPL). The produced mDE-APTES was instrumentally characterized and the obtained results of FTIR analysis and scanning electron microscopy equipped by energy-dispersive X-ray spectroscopy (SEM-EDS) showed successful coating of APTES on mDE surface. PPL was then immobilized onto mDE to obtain the biocatalyst of PPL@mDE (immobilization yield and efficiency of 78.0 ± 0.3% and 80.1 ± 0.6, respectively) and the presence of enzyme was confirmed by EDS method. The attained results of the reusability of PPL@mDE revealed that 57% of the initial activity was retained after 11 cycles of biocatalyst application. PPL@mDE demonstrated higher storage stability than the free enzyme at 4 °C, 25 °C, and 37 °C. The apparent K m (2.35 ± 0.12 mM) and V max (13.01 ± 0.64 µmol/min) values for the immobilized enzyme were considerably altered compared to those of the free enzyme (p > 0.05). PPL@mDE was subsequently employed for the synthesis of banana flavor (isoamyl acetate) in n-hexane, which yields an esterification percentage of 100 at 37 °C after 3 h. However, it merits further investigations to find out about large-scale application of the as-synthesized biocatalyst for esterification.

Tunable Polymeric Scaffolds for Enzyme Immobilization

The number of methodologies for the immobilization of enzymes using polymeric supports is continuously growing due to the developments in the fields of biotechnology, polymer chemistry, and nanotechnology in the last years. Despite being excellent catalysts, enzymes are very sensitive molecules and can undergo denaturation beyond their natural environment. For overcoming this issue, polymer chemistry offers a wealth of opportunities for the successful combination of enzymes with versatile natural or synthetic polymers. The fabrication of functional, stable, and robust biocatalytic hybrid materials (nanoparticles, capsules, hydrogels, or films) has been proven advantageous for several applications such as biomedicine, organic synthesis, biosensing, and bioremediation. In this review, supported with recent examples of enzyme-protein hybrids, we provide an overview of the methods used to combine both macromolecules, as well as the future directions and the main challenges that are currently being tackled in this field.

The Food Matrix and the Gastrointestinal Fluids Alter the Features of Silver Nanoparticles

Silver nanoparticles (AgNPs) are used in the agri-food sector, which can lead to their ingestion. Their interaction with food and their passage through the gastrointestinal tract can alter their properties and influence their fate upon ingestion. Therefore, this study aims at developing an in vitro method to follow the fate of AgNPs in the gastrointestinal tract. After incorporation of AgNPs into a standardized food matrix, a precolonic digestion is simulated and AgNPs are characterized by different techniques. The presence of food influences the AgNPs properties by forming a corona around nanoparticles. Even if the salivary step does not impact significantly the AgNPs, the pH decrease and the digestive enzymes induce the agglomeration of AgNPs during the gastric phase, while the addition of intestinal fluids disintegrates these clusters. AgNPs can thus reach the intestinal cells under nanometric form, although the presence of food and gastrointestinal fluids modifies their properties compared to pristine AgNPs. They can form a corona around the nanoparticles and act as colloidal stabilizer, which can impact the interaction of AgNPs with intestinal epithelium. This study demonstrates the importance of taking the fate of AgNPs in the gastrointestinal tract into account to perform an accurate risk assessment of nanomaterials.

Hierarchical porous and hydrophilic metal-organic frameworks with enhanced enzyme activity

Metal-organic frameworks (MOFs) for enzyme encapsulation-induced biomimetic mineralization under mild reaction conditions are commonly microporous and hydrophobic, which result in a rather high mass transfer resistance of the reactants and restrain the enzyme catalytic activity. Herein, we prepared a type of hierarchical porous and hydrophilic MOF through the biomimetic mineralization of enzymes, zinc ions, 2-methylimidazole, and lithocholic acid. The hierarchical porous structure accelerated the diffusion process of the reactants and the increased hydrophilicity conferred interfacial activity and increased the enzyme catalytic activity. The immobilized enzyme retained higher catalytic activity than the free enzyme and exhibited enhanced resistance to alkaline, organic, and high-temperature conditions. The nanobiocatalyst was reusable and showed long-term storage stability.

Ionic liquids-modified cellulose coated magnetic nanoparticles for enzyme immobilization: Improvement of catalytic performance

In this work, ionic liquids-modified magnetic carboxymethyl cellulose nanoparticles (IL-MCMC) were prepared and used as supports for enzyme immobilization. The specific activity of immobilized lipase PPL-IL-MCMC was 1.43 and 2.81 folds higher than that of free PPL and PPL-MCMC, respectively. Water contact angle analysis indicated that the introduction of ionic liquids increased the hydrophobicity of supports, which in tune induced the lid-opening of lipase, allowing its active sites to become more accessible. In addition, the affinity between lipase and substrate immobilized on the prepared supports was enhanced. The same method was also applied to analyze immobilize penicillin G acylase (PGA) to further investigate the general applicability of the method. The results showed that the immobilized PGA exhibited higher stability than many other reported PGAs. The developed composites may be utilized as excellent supports for enzyme immobilization in industrial application.

Enhanced Thermostability and Anticancer Activity in Breast Cancer Cells of Laccase Immobilized on Pluronic-Stabilized Nanoparticles

Laccases are multi-copper oxidase enzymes having widespread applications in various biotechnological fields. However, low stability of free enzymes restricts their industrial use. Development of effective methods to preserve and even increase the enzymatic activity is critical to maximize their use, though this remains a challenge. In the present study we immobilized Trametes versicolor laccase on pH-responsive (and charge-switchable) Pluronic-stabilized silver nanoparticles (AgNPs^Trp). Our results demonstrate that colloidal stabilization of AgNPs^Trp with the amphiphilic copolymer Pluronic F127 enhances enzyme activity (AgNPsTrpF1 + Lac6) by changing the active site microenvironment, which is confirmed by circular dichroism (CD) and fluorescence spectroscopy. Detailed kinetic and thermodynamic studies reveal a facile strategy to improve the protein quality by lowering the activation energy and expanding the temperature window for substrate hydrolysis. The immobilized nanocomposite did not show any change in flow behavior which indirectly suggests that the enzyme stability is maintained, and the enzyme did not aggregate or unfold upon immobilization. Finally, assessing the anticancer efficacy of this nanocomposite in breast cancer MCF-7 cells shows the inhibition of cell proliferation through β-estradiol degradation and cells apoptosis. To understand the molecular mechanism involved in this process, semi qRT-PCR experiments were performed, which indicated significant decrease in the mRNA levels of anti-apoptotic genes, for example, BCL-2 and NF-kβ, and increase in the mRNA level of pro-apoptotic genes like p53 in treated cells, compared to control. Overall, this study offers a completely new strategy for tailoring nano-bio-interfaces with improved activity and stability of laccase.

Dynamic surface antifouling: mechanism and systems

Marine biofouling is a global problem today. High efficiency and eco-friendly antifouling systems are in pressing need. In recent years, we have proposed the concept of dynamic surface antifouling (DSA). That is, a continuously changing surface can effectively prevent marine fouling organisms from landing and adhesion. Based on this strategy, we developed coatings with dynamic surfaces by using degradable polymers including polyester-polyurethane, modified polyester and poly(ester-co-acrylate). They exhibit tunable renewability, and excellent antifouling and mechanical performance. Moreover, the polymers can serve as carrier and controlled release systems of antifoulants so that they have long service life. This paper reviews the progress and trends in marine anti-biofouling, and presents the mechanism and systems of DSA.

Enantioselective resolution of 2-arylpropionic acid derivatives employing immobilization of lipase from Bacillus subtilis strain Kakrayal_1 (BSK-L)

This work studied the enantioselective resolution of 2-arylpropionic acid derivatives employing immobilization of lipase produced by Bacillus subtilis strain Kakrayal_1 (BSK-L). The efficient immobilization of lipase on modified silica gel was confirmed by Fourier transform infrared spectroscopy. Tethering of lipase facilitated the enhancement of physiochemical properties and stability of enzyme. Covalently immobilized enzyme retained 85% of residual activity even on reuse after 10th reaction cycle. Validation of immobilized lipase for enantioselective resolution of 2-arylpropionic acid derivatives led to 47.8% conversion efficiency with 87% enantiomeric excess (ee) for ketoprofen, and 27.3% conversion efficiency with 75% ee for flurbiprofen. The enantioselective resolution using immobilized lipase (BSK-L) was superior to free and commercially procured lipase, which suggest a potential application of immobilized lipase in the pharmaceutical/chemical industry.