Nonionic surfactants: a key to enhance the enzyme activity at cationic reverse micellar interface

Development of an ELISA-based device to quantify antibody adsorption directly on medical plastic surfaces

Monoclonal antibodies (mAbs) encounter numerous interfaces during manufacturing, storage, and administration. While protein adsorption at the solid/liquid interface has been widely explored on model surfaces, a key challenge remains - the detection of very small amounts of adsorbed mAb directly on real medical surfaces. This study introduces a novel ELISA-based device, ELIBAG, a new tool for measuring mAb adsorption on medical bags. The efficacy of this device was highlighted by successfully confirming the adsorption of an IgG1 on two medical bag types: a polypropylene IV administration bag and a low-density polyethylene pharmaceutical manufacturing bag. We also investigated IgG1 adsorption on plastic model surfaces, revealing a similar range of mAb bulk concentration for surface saturation on both model and bag surfaces. This innovative device, characterized by its high-throughput and rapid approach, paves the way for extensive investigations into therapeutic proteins, such as mAbs, adsorption on a variety of medical or pharmaceutical surfaces, diverse adsorption conditions, and the influence of excipients employed in mAb formulation, which could enhance the knowledge of mAb interactions with plastic surfaces throughout their lifecycle.

An efficient and high-water-content enzymatic esterification method for the synthesis of β-sitosterol conjugated linoleate via a sodium citrate-based three-liquid-phase system

Three-liquid-phase systems (TLPSs) are novel interfacial enzymatic reaction systems that have been successfully applied in many valuable reactions. However, these systems are suitable only for hydrolysis reactions and not for more widely used esterification reactions. Surprisingly, our recent research revealed that two water-insoluble substrates (β-sitosterol and conjugated linoleic acid) could be rapidly esterified in this system. The initial rate of the esterification reaction in the TLPS based on sodium citrate was enhanced by approximately 10-fold relative to that in a traditional water/n-hexane system. The special emulsion structure (S/W1/W2 emulsion) formed may be vital because it not only provides a larger reaction interface but also spontaneously generates a middle phase that might regulate water activity to facilitate esterification. Furthermore, the lipase-enriched phase could be reused at least 8 times without significant loss of catalytic efficiency. Therefore, this TLPS is an ideal enzymatic esterification platform for ester synthesis because it is efficient, convenient to use, and cost-effective.

Impact of Lipid Matrix Composition on Activity of Membranotropic Enzymes Galactonolactone Oxidase from Trypanosoma cruzi and L-Galactono-1,4-Lactone Dehydrogenase from Arabidopsis thaliana in the System of Reverse Micelles

The study of many membrane enzymes in an aqueous medium is difficult due to the loss of their catalytic activity, which makes it necessary to use membrane-like systems, such as reverse micelles of surfactants in nonpolar organic solvents. However, it should be taken into account that the micelles are a simplified model of natural membranes, since membranes contain many different components, a significant part of which are phospholipids. In this work, we studied impact of the main phospholipids, phosphatidylcholine (PC) and phosphatidylethanolamine (PE), on activity of the membrane enzymes using galactonolactone oxidase from Trypanosoma cruzi (TcGAL) and L-galactono-1,4-lactone dehydrogenase from Arabidopsis thaliana (AtGALDH) as examples. Effect of the structure (and charge) of the micelle-forming surfactant itself on the activity of both enzymes has been studied using an anionic surfactant (AOT), a neutral surfactant (Brij-96), and a mixture of cationic and anionic surfactants (CTAB and AOT) as examples. The pronounced effect of addition of PC and PE lipids on the activity of AtGALDH and TcGAL has been detected, which manifests as increase in catalytic activity and significant change in the activity profile. This can be explained by formation of the tetrameric form of enzymes and/or protein-lipid complexes. By varying composition and structure of the micelle-forming surfactants (AOT, CTAB, and Brij-96) it has been possible to change catalytic properties of the enzyme due to effect of the surfactant on the micelle size, lipid mobility, charge, and rigidity of the matrix itself.

Biodegradation of Benzo[a]pyrene by a White-Rot Fungus Phlebia acerina: Surfactant-Enhanced Degradation and Possible Genes Involved

Polycyclic aromatic hydrocarbons (PAHs) are persistent environmental pollutants that pose a threat to human health. Among these PAHs, benzo[a]pyrene (BaP), a five-ring compound, exhibits high resistance to biodegradation. White-rot fungus Phlebia acerina S-LWZ20190614-6 has demonstrated higher BaP degradation capabilities compared with Phanerochaete chrysosporium and P. sordida YK-624, achieving a degradation rate of 57.7% after 32 days of incubation under a ligninolytic condition. To further enhance the biodegradation rate, three nonionic surfactants were used, and the addition of 1 or 2 g·L-1 of polyethylene glycol monododecyl ether (Brij 30) resulted in nearly complete BaP biodegradation by P. acerina S-LWZ20190614-6. Interestingly, Brij 30 did not significantly affect the activity of manganese peroxidase and lignin peroxidase, but it did decrease laccase activity. Furthermore, the impact of cytochrome P450 on BaP degradation by P. acerina S-LWZ20190614-6 was found to be relatively mild. Transcriptomic analysis provided insights into the degradation mechanism of BaP, revealing the involvement of genes related to energy production and the synthesis of active enzymes crucial for BaP degradation. The addition of Brij 30 significantly upregulated various transferase and binding protein genes in P. acerina S-LWZ20190614-6. Hence, the bioremediation potential of BaP by the white-rot fungus P. acerina S-LWZ20190614-6 holds promise and warrants further exploration.

Peptide Amphiphilic Supramolecular Nanogels: Competent Host for Notably Efficient Lipase-Catalyzed Hydrolysis of Water-Insoluble Substrates

The present work depicts the development of stable nanogels in an aqueous medium that were exploited for efficient surface-active lipase-catalyzed hydrolysis of water-insoluble substrates. Surfactant-coated gel nanoparticles (neutral NG1, anionic NG2, and cationic NG3) were prepared from peptide amphiphilic hydrogelator (G1, G2, and G3, respectively) at different hydrophilic and lipophilic balance (HLB). Chromobacterium viscosum (CV) lipase activity towards hydrolysis of water-insoluble substrates (p-nitrophyenyl-n-alkanoates (C4-C10)) in the presence of nanogels got remarkably improved by ~1.7-8.0 fold in comparison to that in aqueous buffer and other self-aggregates. An increase in hydrophobicity of the substrate led to a notable improvement in lipase activity in the hydrophilic domain (HLB>8.0) of nanogels. The micro-heterogeneous interface of small-sized (10-65 nm) nanogel was found to be an appropriate scaffold for immobilizing surface-active lipase to exhibit superior catalytic efficiency. Concurrently, the flexible conformation of lipase immobilized in nanogels was reflected in its secondary structure having the highest α-helix content from the circular dichroism spectra.

Improve Enzymatic Hydrolysis of Lignocellulosic Biomass by Modifying Lignin Structure via Sulfite Pretreatment and Using Lignin Blockers

Even traditional pretreatments can partially remove or degrade lignin and hemicellulose from lignocellulosic biomass for enhancing its enzymatic digestibility, the remaining lignin in pretreated biomass still restricts its enzymatic hydrolysis by limiting cellulose accessibility and lignin-enzyme nonproductive interaction. Therefore, many pretreatments that can modify lignin structure in a unique way and approaches to block the lignin’s adverse impact have been proposed to directly improve the enzymatic digestibility of pretreated biomass. In this review, recent development in sulfite pretreatment that can transform the native lignin into lignosulfonate and subsequently enhance saccharification of pretreated biomass under certain conditions was summarized. In addition, we also reviewed the approaches of the addition of reactive agents to block the lignin’s reactive sites and limit the cellulase-enzyme adsorption during hydrolysis. It is our hope that this summary can provide a guideline for workers engaged in biorefining for the goal of reaching high enzymatic digestibility of lignocellulose.

Mixed micelles and bicontinuous microemulsions: Promising media for enzymatic reactions

Enzymes, the natural catalysts, replace catalysts of chemical origin in a wide spectrum of reactions and generally work under environment friendly conditions. Various strategies are adopted to modify catalytic activities of enzymes further, of which one is application of novel reaction medium. This work reviews applicability of novel media like mixed micelles and bicontinuous microemulsions in enzymatic reactions and points out their capability to play bigger roles in enzyme catalysis. Ionic reverse micelles reduced catalytic activities of enzymes through denaturation. Addition of nonionic surfactant to these reverse micelles led to corresponding mixed micelles and thus restored or sometimes enhanced catalytic abilities of enzymes. Mixed micelles comprising of two nonionic surfactants, bicontinuous microemulsion containing two anionic surfactants also acted as efficient reaction media for enzymes. Even a cationic/anionic/nonionic mixed micelle was found to increase activity of enzyme. Mixed micelles and bicontinuous microemulsions comprising of anionic and zwitterionic surfactants augmented enzyme catalysis. Mixed micelles and bicontinuous microemulsions containing ionic liquid and surfactant also had critical impact on enzyme catalysis. Catalytic abilities of enzymes altered significantly in substrate/surfactant and bile salt/surfactant mixed micelles. Concentrations of individual surfactant, molar ratio of surfactants, and molar ratio of water to total surfactants had notable impacts on enzyme catalysis in those media.

Combining Active Carbonic Anhydrase with Nanogels: Enzyme Protection and Zinc Sensing

Background

Due to its excellent biocompatibility, the polyacrylamide (PAAm) hydrogel has shown great potential for the immobilization of enzymes used in biomedical applications. The major challenge involved is to preserve, during the immobilization process, both the biological activity and the structural integrity of the enzymes. Here we report, for the first time, a proof-of-concept study for embedding active carbonic anhydrase (CA) into polyacrylamide (PAAm) nanogels. By immobilizing CA in these nanogels, we hope to provide important advantages, such as matrix protection of the CA as well as its targeted delivery, and also for potentially using these nanogels as zinc nano-biosensors, both in-vitro and in-vivo.

Methods and Results

Two methods are reported here for CA immobilization: encapsulation and surface conjugation. In the encapsulation method, the common process was improved, so as to best preserve the CA, by 1) using a novel biofriendly nonionic surfactant system (Span 80/Tween 80/Brij 30) and 2) using an Al₂O₃ adsorptive filtration purification procedure. In the surface conjugation method, blank PAAm nanogels were activated by N-hydroxysuccinimide and the CA was cross-linked to the nanogels. The amount of active CA immobilized in the nanoparticles was quantified for both methods. Per 1 g nanogels, the CA encapsulated nanogels contain 11.3 mg active CA, while the CA conjugated nanogels contain 22.5 mg active CA. Also, the CA conjugated nanoparticles successfully measured free Zn²⁺ levels in solution, with the Zn²⁺ dissociation constant determined to be 9 pM.

Conclusion

This work demonstrates universal methods for immobilizing highly fragile bio-macromolecules inside nanoparticle carriers, while preserving their structural integrity and biological activity. The advantages and limitations are discussed, as well as the potential biomedical applications.

Effect of Triton X-100 on the Activity and Selectivity of Lipase Immobilized on Chemically Reduced Graphene Oxides

The effect of support hydrophobicity on lipase activity and substrate selectivity was investigated with and without Triton X-100 (TX-100). Lipases from Thermomyces lanuginosa (TL) and Alcaligenes sp. (QLM) were immobilized on graphene oxide (GO) and a range of chemically reduced graphene oxides (CRGOs) with different levels of surface hydrophobicity. Activity assays using 4-hydroxy-N-propyl-1,8-naphthalimide (NAP) esters of varying chain lengths (NAP-butyrate (NAP-B), NAP-octanoate (NAP-O), and NAP-palmitate (NAP-P)) showed that the activity of immobilized QLM and TL decreased by more than 60% on GO and 80% on CRGO (2 h), with activity decreasing further as surface hydrophobicity of the CRGOs increased. Across the hydrophobicity range of GO/CRGOs, the substrate selectivity of QLM shifted from more readily hydrolyzing NAP-P to NAP-B, while TL retained its substrate selectivity for NAP-O. Lipase TL was also shown to desorb from GO and 2 h CRGO when mixed with NAP-O and NAP-P, whereas QLM did not. Circular dichroism analyses of the lipase α-helix content correlate to the observed activity data, with decreases in the α-helical content (40% in TL and 20% in QLM relative to free lipase) consistent with decreases in activity after immobilization on GO. α-Helical content decreased even further as the surface hydrophobicity of CRGOs increased. Attenuated total reflectance-Fourier transform infrared spectroscopy also showed significant changes to the lipase secondary structure upon immobilization. The addition of TX-100 into the activity assay modified the substrate selectivity of immobilized QLM, improving the activity against NAP-O (90%) and NAP-P (67%) compared to the activity measured without TX-100. It was shown that TX-100 primarily affected the activity of QLM by interacting with the ester substrate and the lipase itself. This study provides an improved understanding of how support hydrophobicity and the presence of TX-100 can affect activity/selectivity of lipases immobilized on hydrophobic supports.

Catalytic Performance of a Recombinant Organophosphate-Hydrolyzing Phosphotriesterase from Brevundimonas diminuta in the Presence of Surfactants

Phosphotriestease (PTE), also known as parathion hydrolase, has the ability to hydrolyze the triester linkage of organophosphate (OP) pesticides and chemical warfare nerve agents, making it highly suitable for environment remediation. Here, we studied the effects of various surfactants and commercial detergents on the esterase activity of a recombinant PTE (His6-tagged BdPTE) from Brevundimonas diminuta. Enzymatic assays indicated that His6-tagged BdPTE was severely inactivated by SDS even at lower concentrations and, conversely, the other three surfactants (Triton X-100, Tween 20, and Tween 80) had a stimulatory effect on the activity, especially at a pre-incubating temperature of 40 °C. The enzyme exhibited a good compatibility with several commercial detergents, such as Dr. Formula® and Sugar Bubble®. The evolution results of pyrene fluorescence spectroscopy showed that the enzyme molecules participated in the formation of SDS micelles but did not alter the property of SDS micelles above the critical micelle concentration (CMC). Structural analyses revealed a significant change in the enzyme’s secondary structure in the presence of SDS. Through the use of the intentionally fenthion-contaminated Chinese cabbage leaves as the model experiment, enzyme–Joy® washer solution could remove the pesticide from the contaminated sample more efficiently than detergent alone. Overall, our data promote a better understanding of the links between the esterase activity of His6-tagged BdPTE and surfactants, and they offer valuable information about its potential applications in liquid detergent formulations.

Partial Purification and Characterisation of Pectinase Produced by Aspergillus niger LFP-1 Grown on Pomelo Peels as a Substrate

In the present study, pectinase was produced by local fungal isolate, Aspergillus niger LFP-1 grown on pomelo peels as a sole carbon source under solid-state fermentation (SSF). The purification process begins with the concentration of crude enzyme using ammonium sulfate precipitation and followed by purification using anion-exchange column chromatography (DEAE-Sephadex) and subsequently using gel filtration column chromatography (Sephadex G-100). On the other hand, the molecular weight of the purified enzyme was determined through SDS-PAGE. The findings revealed the crude enzyme was purified up to 75.89 folds with a specific activity of 61.54 U/mg and the final yield obtained was 0.01%. The molecular mass of the purified pectinase was 48 kDa. The optimum pH and temperature were 3.5 and 50°C, respectively. This enzyme was stable at a range of pH 3.5 to 4.5 and a relatively high temperature (40°C–50°C) for 100 min. The K_m and V_max were found to be 3.89 mg/mL and 1701 U/mg, respectively. Meanwhile, pectin from citrus fruit and the metal ion (Co²⁺) were the best substrate and inducer to enhance pectinase yield, respectively.

Biosynthesis of glyceride glycoside (nonionic surfactant) by amylosucrase, a powerful glycosyltransferase

Amylosucrase (ASase, E.C. 2.4.1.4) is a powerful transglycosylation enzyme that can transfer glucose from sucrose to the hydroxyl (-OH) group of various compounds. In this study, recombinant ASases from Deinococcus geothermalis (DgAS) and Bifidobacterium thermophilum (BtAS) were used to synthesize biosurfactants based on the computational analysis of predicted docking simulations. Successful predictions of the binding affinities, conformations, and three-dimensional structures of three surfactants were computed from receptor-ligand binding modes. DgAS and BtAS were effective in the synthesis of biosurfactants from glyceryl caprylate, glyceryl caprate, and polyglyceryl-2 caprate. The results of the transglycosylation reaction were consistent for both ASases, with glyceryl caprylate acceptor showing the highest concentration, as confirmed by thin layer chromatography. Furthermore, the transglycosylation reactions of DgAS were more effective than those of BtAS. Among the three substrates, glyceryl caprylate glycoside and glyceryl caprate glycoside were successfully purified by liquid chromatography-mass spectrometry (LC-MS) with the corresponding molecular weights.

2D and 3D inkjet printing of biopharmaceuticals - A review of trends and future perspectives in research and manufacturing

There is an ongoing global shift in pharmaceutical business models from small molecule drugs to biologics. This increase in complexity is in response to advancements in our diagnoses and understanding of diseases. With the more targeted approach coupled with its inherently more costly development and manufacturing, 2D and 3D printing are being explored as suitable techniques to deliver more personalised and affordable routes to drug discovery and manufacturing. In this review, we explore first the business context underlying this shift to biopharmaceuticals and provide an update on the latest work exploring discovery and pharmaceutics. We then draw on multiple disciplines to help reveal the shared challenges facing researchers and firms aiming to develop biopharmaceuticals, specifically when using the most commonly explored manufacturing routes of drop-on-demand inkjet printing and pneumatic extrusion. This includes separating out how to consider mechanical and chemical influences during manufacturing, the role of the chosen hardware and the challenges of aqueous formulation based on similar challenges being faced by the printing industry. Together, this provides a review of existing work and guidance for researchers and industry to help with the de-risking and rapid development of future biopharmaceutical products.

Cohnella 1759 cysteine protease shows significant long term half-life and impressive increased activity in presence of some chemical reagents

Thermostability and substrate specificity of proteases are major factors in their industrial applications. rEla is a novel recombinant cysteine protease obtained from a thermophilic bacterium, Cohnella sp.A01 (PTCC No: 1921). Herein, we were interested in recombinant production and characterization of the enzyme and finding the novel features in comparison with other well-studied cysteine proteases. The bioinformatics analysis showed that rEla is allosteric cysteine protease from DJ-1/ThiJ/PfpI superfamily. The enzyme was heterologously expressed and characterized and the recombinant enzyme molecular mass was 19.38 kD which seems to be smaller than most of the cysteine proteases. rEla exhibited acceptable activity in broad pH and temperature ranges. The optimum activity was observed at 50℃ and pH 8 and the enzyme showed remarkable stability by keeping 50% of residual activity after 100 days storage at room temperature. The enzyme Km and Vmax values were 21.93 mM, 8 U/ml, respectively. To the best of our knowledge, in comparison with the other characterized cysteine proteases, rEla is the only reported cysteine protease with collagen specificity. The enzymes activity increases up to 1.4 times in the presence of calcium ion (2 mM) suggesting it as the enzyme's co-factor. When exposed to surfactants including Tween20, Tween80, Triton X-100 and SDS (1% and 4% v/v) the enzyme activity surprisingly increased up to 5 times.

The effect of single CNTs/GNPs and complexes on promoting the interfacial catalytic activity of lipase in conventional emulsions

BACKGROUND

The interfacial activation mechanism of lipase enables it to exhibit high catalytic activity in water-in-oil (W/O) microemulsions. However, W/O microemulsions have obvious defects such as a small water pool and a large demand for surfactants. The present study investigated the substitutability of conventional oil-in-water (O/W) and W/O emulsions as lipase catalytic systems. Carbon nanotubes (CNTs)/gold nanoparticles (GNPs) or CNT-GNP electrostatically bonded complexes were added into the conventional emulsion system.

RESULTS

The simulated biphasic system and fluorescence study showed different and even contradictory results for the interfacial behavior of CNTs and CNT-GNP complexes due to the variation of the dispersibility of CNTs in cetyltrimethylammonium bromide (CTAB). Results also showed that conventional O/W emulsions were more suitable for lipase catalysis than conventional W/O emulsions. When CNTs or CNT_CATB -GNP complexes were added in a conventional O/W emulsion system, the catalytic activity of lipase was significantly promoted (up to 4.8-fold using CNTs and 3.5-fold using CNT_CATB -GNP complexes compared with free lipase).

CONCLUSIONS

The possible reason for this promotion may be due to the increase in the interface area. The current study was not only the latest exploration of lipase activity promotion via nanomaterials, but also explored a new lipase catalytic system and provides further insight into improving the catalytic performance of lipase in conventional emulsions. © 2020 Society of Chemical Industry.

Orientational Switch of the Lipase A Enzyme at the Oil-Water Interface: An Order of Magnitude Increase in Turnover Rate with a Single Surfactant Tag Explained

Interfacially active lipases can be immobilized at a biphasic interface to enhance turnover recyclability and to facilitate product separation. Extensive coarse-grained molecular dynamics simulations of lipase A (LipA) from Bacillus subtilis show a bimodal orientational distribution of the enzyme at an oil-water interface, arising from its ellipsoidal Janus particle-like character. The relative orientational preference can be tuned by pH. The simulations rationalize a rare experimental observation of an order of magnitude increase in the turnover rate of this lipase upon its noncovalent tagging by a single surfactant molecule at the interface, compared to its rate in bulk water. The adsorption free energy, the interfacial activation, a decrease in the number of orientational fluctuations, and an increased rate of translational diffusion, to all of which the Janus character of LipA contributes, are the factors responsible for this enhancement. This study can spur further investigations of the Janus behavior of enzymes to enhance their activity as well as to stabilize the biphasic emulsion needed for interfacial catalysis.

Enzyme activities during Benzo[a]pyrene degradation by the fungus Lasiodiplodia theobromae isolated from a polluted soil

The enzyme activities of the fungus Lasiodiplodia theobromae (L. theobromae) were studied during degradation of benzo[a]pyrene (BaP). The L. theobromae was isolated from a polycyclic aromatic hydrocarbons (PAHs) contaminated soil collected from the Beijing Coking Plant in China and can potentially use BaP as its sole carbon source with a degradation ratio of up to 53% over 10 days. The activities of lignin peroxidase (LiP) and laccase (LAC) could be detected during BaP biodegradation; while manganese peroxidase (MnP) was not detected. Both glucose and salicylic acid enhanced BaP biodegradation slightly. In contrast, the coexistence of phenanthrene (PHE) inhibited BaP degradation. These metabolic substrates all enhanced the secretion of LiP and LAC. The addition of Tween 80 (TW-80) enhanced BaP biodegradation as well as the LiP and LAC activities. At the same time, TW-80 was degraded by the L. theobromae. In addition, the L. theobromae was compared to Phanerochaete chrysosporium (P. chrysosporium), which is a widely studied fungus for degrading PAH. P. chrysosporium was unable to use BaP as its sole carbon source. The activities of LiP and LAC produced by the P. chrysosporium were less than those of the L. theobromae. Additionally, the four intermediates formed in the BaP biodegradation process were monitored using GC-MS analysis. Four metabolite concentrations first increased and then decreased or obtained the platform with prolonged BaP biodegradation time. Therefore, this study shows that the L. theobromae may be explored as a new strain for removing PAHs from the environment.

Takes Two to Tango: Choreography of the Coadsorption of CTAB and Hexanol at the Oil-Water Interface

Mixed surfactant systems at the oil-water interface play a vital role in applications ranging widely from drug delivery to oil-spill remediation. Synergistic mixtures are superior emulsifiers and more effective at modifying surface tension than either component alone. Mixtures of surfactants with dissimilar polar head groups are of particular interest because of the additional degree of control they offer. The interplay of hydrophobic and electrostatic effects in these systems is not well understood, in part because of the difficulty in examining their behavior at the buried oil-water interface where they reside. Here, surface-specific vibrational sum frequency spectroscopy is utilized in combination with surface tensiometry and computational methods to probe the cooperative molecular interactions between a cationic surfactant cetyltrimethylammonium bromide (CTAB) and a nonionic alcohol (1-hexanol) that induce the two initially reluctant surfactants to coadsorb synergistically at the interface. A careful deuteration study of CTAB reveals that hexanol cooperates with CTAB such that both molecules preferentially orient at the interface for sufficiently large enough concentrations of hexanol. This work's methodology is unique and serves as a guide for future explorations of macroscopic properties in these complex systems. Results from this work also provide valuable insights into how interfacial ordering impacts surface tensiometry measurements for nonionic surfactants.

Non-ionic detergents Nonidet P-40 and Triton X-100 increase enzymatic activity of plasmin

Plasmin is a potent serin protease involved in a variety of biological functions, such as fibrinolysis and tissue remodeling. On performing an in vitro control assay to measure the activity of endogenous plasmin in cell lysates, a stimulatory effect of non-ionic detergent NP-40 on plasmin activity was discovered. Another non-ionic detergent, TX-100, also enhanced plasmin activity, while ionic detergents sodium deoxycholate and sodiem dodecyl sulfate abolished plasmin enzyme activity. Kinetic analysis of plasmin activity in the presence of NP-40 and TX-100 demonstrated an increase in V_max; however, there was no change in K_m values, suggesting that these detergents stimulate plasmin activity in a non-competitive manner. Fibrin plate assay indicates that NP-40 and TX-100 functionally stimulate plasmin activity by showing a dose-dependent increase in fibrinolysis.

Highly Efficient and Enzyme-Recoverable Method for Enzymatic Concentrating Omega-3 Fatty Acids Generated by Hydrolysis of Fish Oil in a Substrate-Constituted Three-Liquid-Phase System

A novel three-liquid-phase system which contained fish oil as the nonpolar phase was developed for the lipase-based hydrolysis of fish oil and subsequent enrichment of the omega-3 polyunsaturated fatty acids (n-3 PUFA) in the glyceride fraction of the fish oil. In comparison with the traditional oil/water system, the enrichment factor of n-3 PUFA in this system was increased by 363.4% as a result of a higher dispersity, higher selectivity of the lipase for the other fatty acids except for n-3PUFA, and relief of product inhibition. The content of n-3 PUFA in the glyceride fraction could be concentrated to 67.97% by repeated hydrolysis after removing the free fatty acids. Furthermore, the lipase could be reused for at least eight rounds. This method would be an ideal approach for enriching n-3 PUFA because it is cost-effective, low in toxicity, and easily scaled up.

Optimization and in Silico Analysis of a Cold-Adapted Lipase from an Antarctic Pseudomonas sp. Strain AMS8 Reaction in Triton X-100 Reverse Micelles

A moderate yield of a purified enzyme can be achieved by using the simple technique of reverse micellar extraction (RME). RME is a liquid–liquid extraction method that uses a surfactant and an organic solvent to extract biomolecules. Instead of traditional chromatographic purification methods, which are tedious and expensive, RME using the nonionic surfactant Triton X-100 and toluene is used as an alternative purification technique to purify a recombinant cold-adapted lipase, AMS8. Various process parameters were optimized to maximize the activity recovery of the AMS8 lipase. The optimal conditions were found to be 50 mM sodium phosphate buffer, pH 7, 0.125 M NaCl, and 0.07 M Triton X-100 in toluene at 10 °C. Approximately 56% of the lipase activity was successfully recovered. Structural analysis of the lipase in a reverse micelle (RM) was performed using an in silico approach. The predicted model of AMS8 lipase was simulated in the Triton X-100/toluene reverse micelles from 5 to 40 °C. The lid 2 was slightly opened at 10 °C. However, the secondary structure of AMS8 was most affected in the non-catalytic domain compared to the catalytic domain, with an increased coil conformation. These results suggest that an AMS8 lipase can be extracted using Triton X-100/water/toluene micelles at low temperature. This RME approach will be an important tool for the downstream processing of recombinant cold-adapted lipases.

Structural Characterization of Biocompatible Reverse Micelles Using Small-Angle X-ray Scattering, 31P Nuclear Magnetic Resonance, and Fluorescence Spectroscopy

The most critical problem regarding the use of reverse micelles (RMs) in several fields is the toxicity of their partial components. In this sense, many efforts have been made to characterize nontoxic RM formulations on the basis of biological amphiphiles and/or different oils. In this contribution, the microstructure of biocompatible mixed RMs formulated by sodium 1,4-bis-2-ethylhexylsulfosuccinate (AOT) and tri- n-octylphosphine oxide (TOPO) surfactants dispersed in the friendly solvent methyl laurate was studied by using SAXS and ³¹P NMR and by following the solvatochromic behavior of the molecular probe 4-aminophthalimide (4-AP). The results indicated the presence of RM aggregates upon TOPO incorporation with a droplet size reduction and an increase in the interfacial fluidity in comparison with pure AOT RMs. When confined inside the mixed systems, 4-AP showed a red-edge excitation shift and confirmed the increment of interfacial fluidity upon TOPO addition. Also, the partition between the external nonpolar solvent and the RM interface and an increase in both the local micropolarity and the capability to form a hydrogen bond interaction between 4-AP and a mixed interface were observed. The findings have been explained in terms of the nonionic surfactant structure and its complexing nature expressed at the interfacial level. Notably, we show how two different approaches, i.e., SAXS and the solvatochromism of the probe 4-AP, can be used in a complementary way to enhance our understanding of the interfacial fluidity of RMs, a parameter that is difficult to measure directly.

Micellar Enzymology for Thermal, pH, and Solvent Stability

This chapter describes methods for enzyme stabilization using micellar solutions. Micellar solutions have been shown to increase the thermal stability, as well as the pH and solvent tolerance of enzymes. This field is traditionally referred to as micellar enzymology. This chapter details the use of ionic and nonionic micelles for the stabilization of polyphenol oxidase, lipase, and catalase, although this method could be used with any enzymatic system or enzyme cascade system.

How Does Interfacial Hydration Alter during Rod to Sphere Transition in DDAB/Water/Cyclohexane Reverse Micelles? Insights from Excited State Proton Transfer and Fluorescence Anisotropy

How does microscopic organization of an organized assembly alter during macroscopic structural transition? The question may be important to ascertain driving forces responsible for such transitions. Didodecyldimethylammonium bromide (DDAB)/water/cyclohexane reverse micelle is an attractive assembly that undergoes structural transition from rod to spherical shape when the amount of water loading, w0 ([water]/[surfactant]), exceeds a particular value (w0 ∼ 8). Here, we intend to investigate the effect of the morphological change upon interfacial hydration using steady-state and time-resolved fluorescence measurements. The anionic fluorophore 8-hydroxypyrene-1,3,6-trisulfonate (HPTS or pyranine) is expected to be trapped within the positively charged RM interface. The fluorophore can undergo excited-state proton transfer (ESPT) in the presence of water and, thus, is able to provide insight on the level of hydration within the interface. The ESPT process is markedly inhibited within the interface at low w0 and gradually favored with increase of w0. The time-resolved fluorescence decays could be best analyzed by assuming distribution of HPTS over two distinct interfacial regions- partly hydrated and mostly dehydrated. The relative population of the two regions varies distinctly at low w0 (<6) and high w0 (>6) regimes. Moreover, fluorescence anisotropy (steady-state and time-resolved) varies differently with respect to w0, before and after the transition point (w0 ∼ 8).

Nanoscale Control Over Interfacial Properties in Mixed Reverse Micelles Formulated by Using Sodium 1,4-bis-2-ethylhexylsulfosuccinate and Tri-n-octyl Phosphine Oxide Surfactants

The interfacial properties of pure reverse micelles (RMs) are a consequence of the magnitude and nature of noncovalent interactions between confined water and the surfactant polar head. Addition of a second surfactant to form mixed RMs is expected to influence these interactions and thus affect these properties at the nanoscale level. Herein, pure and mixed RMs stabilized by sodium 1,4-bis-2-ethylhexylsulfosuccinate and tri-n-octyl phosphine oxide (TOPO) surfactants in n-heptane were formulated and studied by varying both the water content and the TOPO mole fraction. The microenvironment generated was sensed by following the solvatochromic behavior of the 1-methyl-8-oxyquinolinium betaine probe and (31) P NMR spectroscopy. The results reveal unique properties of mixed RMs and we give experimental evidence that free water can be detected in the polar core of the mixed RMs at very low water content. We anticipate that these findings will have an impact on the use of such media as nanoreactors for many types of chemical reactions, such as enzymatic reactions and nanoparticle synthesis.

Hydrophobically Tailored Carbon Dots toward Modulating Microstructure of Reverse Micelle and Amplification of Lipase Catalytic Response

This article delineates the modulation of microstructure of cationic reverse micelle utilizing hydrophobically modified carbon dots (CDs) with varying surface functionalizations. Citric acid was used as the source of the carbon core, and Na-salt of glycine, glycine, Na-salt of 11-aminoundecanoic acid, 11-aminoundecanoic acid, and n-hexadecylamine were used for the surface fabrication of CDs to produce CD 1s, CD 1a, CD 2s, CD 2a, and CD 3, respectively. All these CDs having dimension of 5-7 nm were characterized by spectroscopic and microscopic techniques. The hydrodynamic diameter of cetyltrimethylammonium bromide (CTAB) reverse micelle (CTAB/isooctane/n-hexanol/water) at z ([cosurfactant]/[surfactant]) = 6.4 and W0 ([water]/[surfactant]) = 44 is around 15-20 nm. Interestingly, the size of the water-in-oil (w/o) microemulsions dramatically increased up to 120-200 nm upon doping hydrophobic surface functionalized CD 2a and CD 3. This is possibly due to change in the micellar exchange dynamics and reorganization of the micellar aggregates via hydrophobic interaction between surfactant (CTAB) tail and hydrophobic surface modifier of the carbon dots. However, no alteration in the size of reverse micelles was noted in the presence of carbon dots CD 1s, CD 1a, and CD 2s. Spectroscopic and microscopic investigations confirmed that the hydrophobic CD 2a and CD 3 were localized at the interface of reverse micelles whereas CD 1s, CD 1a, and CD 2s were possibly located in the water pool (away from interface). The activity of Chromobacterium viscosum lipase encapsulated within CD 3 and CD 2a doped significantly large CTAB reverse micelles showed remarkable improvement (3.7-fold and 3.4-fold) in its catalytic response. However, hydrophilic carbon dots CD 1s and CD 2s as well as moderately hydrophobic CD 1a had no significant effect on the microstructure of reverse micelles as well as on the lipase activity.

Synergistic interactions of surfactant blends in aqueous medium are reciprocated in non-polar medium with improved efficacy as a nanoreactor

Efficient soft chemical nanoreactors: a design strategy to improve the performance of a model C–C cross coupling (Heck) reaction under nanoscopic confinement of surfactant blends.

Unusually high thermal stability and peroxidase activity of cytochrome c in ionic liquid colloidal formulation

All ionic liquid-based colloidal formulation as a thermally stable medium for enzyme biocatalysis.

Wet Interface of Benzylhexadecyldimethylammonium Chloride Reverse Micelle Revealed by Excited State Proton Transfer of a Localized Probe

Excited state proton transfer (ESPT) of an anionic photoacid 8-hydroxypyrene-1,3,6-trisulfonic acid (HPTS or pyranine) has been studied inside a cationic reverse micelle (RM), water/benzylhexadecyldimethylammonium chloride (BHDC)/benzene, using steady-state and time-resolved fluorescence spectroscopy. The observed ESPT behavior is found to be remarkably different from the known ESPT trend of HPTS inside anionic AOT and cationic CTAB RMs; the ESPT dynamics approaches that of bulk water at higher w0 (≥10) inside AOT RM while no ESPT was observed for CTAB reverse micelle [ Sedgwick J. Am. Chem. Soc. 2012 , 134 , 11904 - 11907 ]. The ESPT dynamics inside BHDC RM is remarkably slower compared to that of water at all w0 (= [water]/[surfactant]) values and relatively much less sensitive to w0 variation compared to AOT RM. 2D NOESY and fluorescence anisotropy measurements reveal that the probe (HPTS) is embedded inside the positive interface of BHDC RM. Despite its trapped location, HPTS is able to undergo ESPT due to significant penetration of water molecules into the interface. Furthermore, facile ESPT at higher w0 is consistent with higher degree of interface hydration as predicted by a recent MD simulation [ Agazzi Langmuir 2014 , 30 , 9643 - 9653 ]. The study shows that ESPT dynamics inside RM varies not only with the interface charge but also on the nature of the headgroup and solvation.

Buffers more than buffering agent: introducing a new class of stabilizers for the protein BSA

In this study, we have analyzed the influence of four biological buffers on the thermal stability of bovine serum albumin (BSA) using dynamic light scattering (DLS).

Gold nanoparticles tune the activity of laccase in anionic reverse micelles

The interfacial property of reverse micelles is an important factor affecting the catalytic activity of enzymes hosted in the micelles. In this article, the effect of gold nanoparticles (GNPs) on the catalytic activity of laccase (non-surface-active enzyme) and the related mechanism are reported. It was found that laccase activity was dependent on the size of the particle and its concentration as well as on the water content and the concentration of AOT. It was shown that there existed several types of micelles in the present reverse micellar system in the presence of GNPs. The population of the various micelles depended on the concentrations of both GNPs and AOT. Fluorescence and circular dichroism spectra of laccase at different water contents and GNP concentrations indicated that the conformation of laccase and its activity were tuned by GNPs via changing the structure of the reverse micelles. Analysis showed that changes in the thickness of the water layer (Lw) and in the apparent occupied area of individual AOT molecules (AAOT) caused by GNPs were the main parameters affecting the activity of laccase. The present work extends and deepens the understanding of the tuning mechanism of GNPs on enzymatic performance in reverse micelles and provides guidance for rational design of the optimal microenvironment of laccase.

Does the optimum hydrophilic lipophilic balance condition affect the physical properties of mixed reverse micelles? A spectroscopic investigation

Synergism in several physical properties as realized in many mixed surfactant reverse micellar (RM) systems often manifests optimum hydrophilic-lipophilic balance (HLB), interdroplet interaction, or both. Such synergism is often desired for specific applications of RM systems; however, a proper rationale on the effect of such phenomenon imparted on the structure, dynamics, and activity of water molecules in RM waterpool is strongly demanded. In the present contribution we have investigated how the optimum HLB condition of mixed RM composed two nonionic surfactants (Igepal 210 and Igepal 630) affects the physical properties of entrapped water molecules in the RM waterpool. The studied mixed RM exhibits synergistic water solubilization behavior as a function of the mixing ratio with a maximum in solubilization capacity being reached at X(Ig630) = 0.3. Dynamic light scattering (DLS) studies show a bimodal distribution of droplet size in this region, whereas it is monomodal in terminal compositions. Fourier transform infrared spectroscopy (FTIR) study in the 3000-3800 cm(-1) region identifies a linear trend in which the content of "bound" water increases at the expense of the "network" water as the content of the hydrophilic surfactant Igepal 630 is increased in the mixture. Subnanosecond relaxation dynamics of the entrapped water as revealed by the fluoroprobe coumarin 500 corroborates a similar linear trend as observed in the FTIR measurements as the rotational diffusion gets retarded with the increase of ethylene oxide chain length of Igepal. Reaction kinetics of solvolysis of benzoyl chloride reaction, however, does not offer any linear trend as it gets slower in the optimum HLB region, the nonlinearity being a consequence of the distribution of the substrate in the different phases.