Antifungal potential of the new copper(II)-theophylline/1,10-phenanthroline complex against drug-resistant Candida species.

Candida spp. are the commonest fungal pathogens worldwide. Antifungal resistance is a problem that has prompted the discovery of novel anti-Candida drugs. Herein, 25 compounds, some of them containing copper(II), cobalt(II) and manganese(II) ions, were initially evaluated for inhibiting the growth of reference strains of Candida albicans and Candida tropicalis. Eight (32%) of the compounds inhibited the proliferation of these yeasts, displaying minimum inhibitory concentrations (MICs) ranging from 31.25 to 250 µg/mL and minimum fungicidal concentration (MFCs) from 62.5 to 250 µg/mL. Drug-likeness/pharmacokinetic calculated by SwissADME indicated that the 8 selected compounds were suitable for use as topical drugs. The complex CTP, Cu(theo)2phen(H2O).5H2O (theo = theophylline; phen = 1,10-phenanthroline), was chosen for further testing against 10 medically relevant Candida species that were resistant to fluconazole/amphotericin B. CTP demonstrated a broad spectrum of action, inhibiting the growth of all 20 clinical fungal isolates, with MICs from 7.81 to 62.5 µg/mL and MFCs from 15.62 to 62.5 µg/mL. Conversely, CTP did not cause lysis in erythrocytes. The toxicity of CTP was evaluated in vivo using Galleria mellonella and Tenebrio molitor. CTP had no or low levels of toxicity at doses ranging from 31.25 to 250 µg/mL for 5 days. After 24 h of treatment, G. mellonella larvae exhibited high survival rates even when exposed to high doses of CTP (600 µg/mL), with the 50% cytotoxic concentration calculated as 776.2 µg/mL, generating selectivity indexes varying from 12.4 to 99.4 depending on each Candida species. These findings suggest that CTP could serve as a potential drug to treat infections caused by Candida species resistant to clinically available antifungals.

Extending the computational and experimental analysis of lipase active site selectivity.

Molecular docking is an important computational analysis widely used to predict the interaction of enzymes with several starting materials for developing new valuable products from several starting materials, including oils and fats. In the present study, molecular docking was used as an efficient in silico screening tool to select biocatalysts with the highest catalytic performance in butyl esters production in a solvent-free system, an eco-friendly approach, via direct esterification of free fatty acids from Licuri oil with butanol. For such purpose, three commercial lipase preparations were used to perform molecular docking studies such as Burkholderia cepacia (BCL), Porcine pancreatic (PPL), and Candida rugosa (CRL). Concurrently, the results obtained in BCL and CRL are the most efficient in the esterification process due to their higher preference for catalyzing the esterification of lauric acid, the main fatty acid found in the licuri oil composition. Meanwhile, PPL was the least efficient because it preferentially interacts with minor fatty acids. Molecular docking with the experimental results indicated the better performance in the synthesis of esters was BCL. In conclusion, experimental results analysis shows higher enzymatic productivity in esterification reactions of 1294.83 µmol/h.mg, while the CRL and PPL demonstrated the lowest performance (189.87 µmol / h.mg and 23.96 µmol / h.mg, respectively). Thus, molecular docking and experimental results indicate that BCL is a more efficient lipase to produce fatty acids and esters from licuri oil with a high content of lauric acid. In addition, this study also demonstrates the application of molecular docking as an important tool for lipase screening to achieve more sustainable production of butyl esters with a view synthesis of biolubricants.

Experimental and Computational Analysis of Synthesis Conditions of Hybrid Nanoflowers for Lipase Immobilization.

This work presents a framework for evaluating hybrid nanoflowers using Burkholderia cepacia lipase. It was expanded on previous findings by testing lipase hybrid nanoflowers (hNF-lipase) formation over a wide range of pH values (5-9) and buffer concentrations (10-100 mM). The free enzyme activity was compared with that of hNF-lipase. The analysis, performed by molecular docking, described the effect of lipase interaction with copper ions. The morphological characterization of hNF-lipase was performed using scanning electron microscopy. Fourier Transform Infrared Spectroscopy performed the physical-chemical characterization. The results show that all hNF-lipase activity presented values higher than that of the free enzyme. Activity is higher at pH 7.4 and has the highest buffer concentration of 100 mM. Molecular docking analysis has been used to understand the effect of enzyme protonation on hNF-lipase formation and identify the main the main binding sites of the enzyme with copper ions. The hNF-lipase nanostructures show the shape of flowers in their micrographs from pH 6 to 8. The spectra of the nanoflowers present peaks typical of the amide regions I and II, current in lipase, and areas with P-O vibrations, confirming the presence of the phosphate group. Therefore, hNF-lipase is an efficient biocatalyst with increased catalytic activity, good nanostructure formation, and improved stability.

Evaluation of lipase access tunnels and analysis of substance transport in comparison with experimental data.

Lipases (E.C. 3.1.1.3) have buried active sites and used access tunnels in the transport of substrates and products for biotransformation processes. Computational methods are used to predict the trajectory and energy profile of ligands through these tunnels, and they complement the experimental methodologies because they filter data, optimizing laboratory time and experimental costs. Access tunnels of Burkholderia cepacia lipase (BCL), Candida rugosa lipase (CRL), and porcine pancreas lipase (PPL) and the transport of fatty acids, alcohols and esters through the tunnels were evaluated using the online server CaverWeb V1.0, and server calculation results were compared with experimental data (productivity). BCL showed higher productivity with palmitic acid-C16:0 (4029.95 µmol/h mg); CRL obtained productivity for oleic acid-C18:1 (380.80 µmol/h mg), and PPL achieved productivity for lauric acid-C12:0 (71.27 µmol/h mg). The highest probability of transport for BCL is through the tunnels 1 and 2, for CRL through the tunnel 1, and for PPL through the tunnels 1, 2, 3 and 4. Thus, the best in silico result was the transport of the substrates palmitic acid and ethanol and product ethyl palmitate in tunnel 1 of BCL. This result corroborates with the best result for the productivity data (higher productivity for BCL with palmitic acid-4029.95 µmol/h mg). The combination of in silico evaluation and experimental data gave similar results, demonstrating that in silico approaches are a promising alternative for reducing screening tests and minimizing laboratory time in the bio-catalysis area by identifying the lipases with the greatest reaction potential, as in the case of this proposal.

Enhanced Enzyme Reuse through the Bioconjugation of L-Asparaginase and Silica-Based Supported Ionic Liquid-like Phase Materials.

L-asparaginase (ASNase) is an amidohydrolase that can be used as a biopharmaceutical, as an agent for acrylamide reduction, and as an active molecule for L-asparagine detection. However, its free form displays some limitations, such as the enzyme's single use and low stability. Hence, immobilization is one of the most effective tools for enzyme recovery and reuse. Silica is a promising material due to its low-cost, biological compatibility, and tunable physicochemical characteristics if properly functionalized. Ionic liquids (ILs) are designer compounds that allow the tailoring of their physicochemical properties for a given task. If properly designed, bioconjugates combine the features of the selected ILs with those of the support used, enabling the simple recovery and reuse of the enzyme. In this work, silica-based supported ionic liquid-like phase (SSILLP) materials with quaternary ammoniums and chloride as the counterion were studied as novel supports for ASNase immobilization since it has been reported that ammonium ILs have beneficial effects on enzyme stability. SSILLP materials were characterized by elemental analysis and zeta potential. The immobilization process was studied and the pH effect, enzyme/support ratio, and contact time were optimized regarding the ASNase enzymatic activity. ASNase-SSILLP bioconjugates were characterized by ATR-FTIR. The bioconjugates displayed promising potential since [Si][N3444]Cl, [Si][N3666]Cl, and [Si][N3888]Cl recovered more than 92% of the initial ASNase activity under the optimized immobilization conditions (pH 8, 6 × 10-3 mg of ASNase per mg of SSILLP material, and 60 min). The ASNase-SSILLP bioconjugates showed more enhanced enzyme reuse than reported for other materials and immobilization methods, allowing five cycles of reaction while keeping more than 75% of the initial immobilized ASNase activity. According to molecular docking studies, the main interactions established between ASNase and SSILLP materials correspond to hydrophobic interactions. Overall, it is here demonstrated that SSILLP materials are efficient supports for ASNase, paving the way for their use in the pharmaceutical and food industries.

Enzymatic transesterification of coconut oil by using immobilized lipase on biochar: An experimental and molecular docking study.

Guava seed biochar appears as a new alternative of the effective support to the immobilization of Burkholderia cepacia lipase (BCL) by physical adsorption. The objective of this work was to evaluate the potential of this immobilized biocatalyst in the transesterification reaction of crude coconut oil and ethanol and to understand the mechanism of the reaction through the study of molecular docking. The best loading of BCL was determined to be 0.15 genzyme /gsupport having a hydrolytic activity of 260 U/g and 54% immobilization yield. The products of transesterification reaction produced a maximum yield at 40 °C under different reaction conditions. The monoacylglycerols (MAGs) conversion of 59% was using substrate molar ratio oil:ethanol of 1:7 with the reaction time of 24 H. In addition, the highest ethyl esters yield (48%) had the molar ratio of 1:7 with the reaction time of 96 H and maximum conversion of diacylglycerols (DAGs) was 30% with the molar ratio of 1:6 with the reaction time of 24 H. Molecular Docking was applied to clarify the mechanisms of transesterification reaction at the molecular level. MAGs and DAGs are compounds with excellent emulsifying properties used in industrial production of several bioproducts such as cosmetic, pharmaceuticals, foods, and lubricants.

Computational and experimental analysis on the preferential selectivity of lipases for triglycerides in Licuri oil.

In the present study, we demonstrated the use of molecular docking as an efficient in silico screening tool for lipase-triglyceride interactions. Computational simulations using the crystal structures from Burkholderia cepacia lipase (BCL), Thermomyces lanuginosus lipase (TLL), and pancreatic porcine lipase (PPL) were performed to elucidate the catalytic behavior with the majority triglycerides present in Licuri oil, as follows: caprilyl-dilauryl-glycerol (CyLaLa), capryl-dilauryl-glycerol (CaLaLa), capryl-lauryl-myristoyl-glycerol (CaLaM), and dilauryl-myristoyl-glycerol (LaLaM). The computational simulation results showed that BCL has the potential to preferentially catalyze the major triglycerides present in Licuri oil, demonstrating that CyLaLa, (≈25.75% oil composition) interacts directly with two of the three amino acid residues in its catalytic triad (Ser87 and His286) with the lowest energy (-5.9 kcal/mol), while other triglycerides (CaLaLa, CaLaM, and LaLaM) interact with only one amino acid (His286). In one hard, TLL showed a preference for catalyzing the triglyceride CaLaLa also interacting with His286 residue, but, achieving higher binding energies (-5.3 kcal/mol) than found in BCL (-5.7 kcal/mol). On the other hand, PPL prefers to catalyze only with LaLaM triglyceride by His264 residue interaction. When comparing the computational simulations with the experimental results, it was possible to understand how BCL and TLL display more stable binding with the majority triglycerides present in the Licuri oil, achieving conversions of 50.86 and 49.01%, respectively. These results indicate the production of fatty acid concentrates from Licuri oil with high lauric acid content. Meanwhile, this study also demonstrates the application of molecular docking as an important tool for lipase screening to reach a more sustainable production of fatty acid concentrates from vegetable oils.

Design for preparation of more active cross-linked enzyme aggregates of Burkholderia cepacia lipase using palm fiber residue.

A new design of cross-linked enzyme aggregates (CLEAs) of Burkholderia cepacia lipase (BCL) based mainly on the use of lignocellulosic residue of palm fiber as an additive was proposed. Different parameters for the preparation of active CLEAs in the hydrolysis of olive oil, such as precipitation agents, crosslinking agent concentration, additives, and coating agents were investigated. The highest activity yield (121.1 ± 0.1%) and volumetric activity (1578.1 ± 2.5 U/mL) were achieved for CLEAs prepared using the combination of a coating step with Triton® X-100 and polyethyleneimine plus the use of palm fiber as an additive. The variations of the secondary structures of BCL-CLEAs were analyzed by second-derivative infrared spectra, mainly indicating a reduction of the α-helix structure, which was responsible for the lipase activation in the supramolecular structure of the CLEAs. Thus, these results provided evidence of an innovative design of BCL-CLEAs as a sustainable and biocompatible opportunity for biotechnology applications.

Continuous flow reactor based with an immobilized biocatalyst for the continuous enzymatic transesterification of crude coconut oil.

Here, we have assessed the use of one packed bed or two packed bed reactors in series in which Burkholderia cepacia lipase (BCL) was immobilized on protic ionic liquid (PIL)-modified silica and used as a biocatalyst for the transesterification of crude coconut oil. Reaction parameters including volumetric flow, temperature, and molar ratio were evaluated. The conversion of transesterification reaction products (ethyl esters) was determined using gas chromatography and the quantities of intermediate products (diglyceride and monoglyceride [MG]) were assessed using high-performance liquid chromatography. Packed bed reactors in series produced ethyl esters with the greatest efficiency, achieving 65.27% conversion after 96 H at a volumetric flow rate of 0.50 mL Min-1 at 40 °C and a 1:9 molar ratio of oil to ethanol. Further, within the first 24 H of the reaction, increased MG (54.5%) production was observed. Molecular docking analyses were performed to evaluate the catalytic step of coconut oil transesterification in the presence of BCL. Molecular docking analysis showed that triglycerides have a higher affinity energy (-5.7 kcal mol-1 ) than the smallest MG (-6.0 kcal mol-1 ), therefore, BCL catalyzes the conversion of triglycerides rather than MG, which is consistent with experimental results.

ß-Cyclodextrin/Isopentyl Caffeate Inclusion Complex: Synthesis, Characterization and Antileishmanial Activity.

Isopentyl caffeate (ICaf) is a bioactive ester widely distributed in nature. Our patented work has shown promising results of this molecule against Leishmania. However, ICaf shows poor solubility, which limits its usage in clinical settings. In this work, we have proposed the development of an inclusion complex of ICaf in ß-cyclodextrin (ß-CD), with the aim to improve the drug solubility, and thus, its bioavailability. The inclusion complex (ICaf:ß-CD) was developed applying three distinct methods, i.e., physical mixture (PM), kneading (KN) or co-evaporation (CO) in different molar proportions (0.25:1, 1:1 and 2:1). Characterization of the complexes was carried out by thermal analysis, Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and molecular docking. The ICaf:ß-CD complex in a molar ratio of 1:1 obtained by CO showed the best complexation and, therefore, was selected for further analysis. Solubility assay showed a marked improvement in the ICaf:ß-CD (CO, 1:1) solubility profile when compared to the pure ICaf compound. Cell proliferation assay using ICaf:ß-CD complex showed an IC50 of 3.8 and 2.7 µg/mL against L. amazonesis and L. chagasi promastigotes, respectively. These results demonstrate the great potential of the inclusion complex to improve the treatment options for visceral and cutaneous leishmaniases.

Optimization of the enzymatic hydrolysis of Moringa oleifera Lam oil using molecular docking analysis for fatty acid specificity.

Alternative strategies are required to develop the optimized production of fatty acids using biocatalysis; molecular docking and response surface methodology are efficient tools to achieve this goal. In the present study, we demonstrate a novel and robust methodology for the sustainable production of fatty acids from Moringa oleifera Lam oil using lipase-catalyzed hydrolysis (without the presence of emulsifiers or buffer solutions). Seven commercial lipases from Candida rugosa (CRL), Burkholderia cepacia (BCL), Thermomyces lanuginosus (TLL), Rhizopus niveus (RNL), Pseudomonas fluorescens (PFL), Mucor javanicus (MJL), and porcine pancreas (PPL) were used as biocatalysts. Initial screening showed that CRL had the highest hydrolytic activity (hydrolysis degree of 81%). Molecular docking analysis contributed to the experimental results, showing that CRL displays more stable binding free energy with oleic acid (C18:1), which is the fatty acid of highest concentration in Moringa oleifera Lam oil. To evaluate and optimize the hydrolysis process, response surface methodology (RSM) was used. The effect of temperature, mass ratio oil:water, and hydrolytic activity on enzymatic hydrolysis was evaluated by central composite design using RSM. Under the optimized conditions (temperature of 37 °C, mass ratio oil:water of 25%, and hydrolytic activity of 550 U goil -1 ), the maximum hydrolysis degree (100%) was achieved. The present study provides a robust method for the enzymatic hydrolysis of different oils for efficient and sustainable fatty acid production.

Understanding the Effect of Ionic Liquids as Adjuvants in the Partition of Biomolecules in Aqueous Two-Phase Systems Formed by Polymers and Weak Salting-Out Agents.

Ionic liquids (ILs) as adjuvants in polymer-salt aqueous two-phase systems (ATPS) have been used to improve the extraction of biomolecules. However, the impact of ILs as adjuvants on the partition of biomolecules is still poorly understood. Previous works mostly focused on ATPS based on strong salting-out agents, which may mask the IL effect. In this work, ATPS formed by polyethylene glycol (PEG 400) and a weak salting-out salt ((NH4)2SO4) with a wide number of ILs as adjuvants (chloride-based combined with cholinium, imidazolium, pyrrolidinium, piperidinium, tetralkylammonium and tetralkylphosphonium cations) were investigated. The respective phase diagrams were determined, and the systems extraction performance for a wide range of biomolecules (phenolic compounds, alkaloids and amino acids) was investigated. The results obtained show that ILs as adjuvants in polymer-salt ATPS modulate the partition of biomolecules. In particular, more hydrophobic ILs significantly enhance the partition of more hydrophobic biomolecules to the PEG-rich phase (where the IL is enriched). Furthermore, the intensity of the IL effect is more pronounced when using weak salting-out agents. A linear correlation between the biomolecules and the ILs partition coefficients, and with the biomolecules octanol-water partition coefficients, was found. In most ATPS formed by polymers and salts using ILs as adjuvants, the biomolecules partition is driven by the ILs partition and by the difference in hydrophobicity between the coexisting phases.

Evaluation of the effect of ionic liquids as adjuvants in polymer-based aqueous biphasic systems using biomolecules as molecular probes.

Aqueous biphasic systems (ABS) have been largely investigated for the extraction, separation and/or purification of biomolecules. Recently, the use of ionic liquids (ILs) as additives in conventional polymer-based ABS was proposed to overcome the limited range of polarities of the coexisting phases. However, the impact of ILs on the partitioning of biomolecules on IL additivated ABS is not universal and is still poorly understood. Aiming at obtaining additional insights on this matter, the effects of the chemical structure of the IL, tie-line length (TLL) and biomolecule nature upon the partition of a series of model biomolecules were investigated. For this purpose, ternary ABS (composed of polyethylene glycol (PEG) 400, citrate buffer at pH 7.0, and water), and several quaternary ABS (composed of PEG 400, citrate buffer at pH 7.0, water and ILs at 5 wt%), were prepared using different chloride-based ILs ([C4mim]Cl, [C4mpyr]Cl, [C4mpip]Cl, [P4444]Cl and [N4444]Cl). The partition of a wide range of biomolecules in these systems (gallic acid, vanillic acid, eugenol, nicotine, caffeine, l-tryptophan, l-phenylalanine and l-tyrosine), used here as molecular probes, was studied. These solutes were chosen due to their wide range of polarities. The results obtained support the concept that ILs, when used as adjuvants in polymer-based ABS, change the coexisting phases' characteristics and modify the partition behavior of biomolecules. In general, a positive effect derived from the use of ILs as adjuvants in PEG-salt systems is observed, particularly when dealing with more hydrophobic biomolecules, whereas IL + salt ABS perform better in the extraction of more hydrophilic biomolecules. The favourable partition of more hydrophilic biomolecules in IL + salt ABS seems to be ruled by specific interactions with the IL, while the favourable partition of more hydrophobic biomolecules in PEG + salt and PEG + salt + IL seems to be governed by the differences in the phases hydrophobicities. It is shown that ILs preferentially migrate to the PEG-rich phase, and that there is a correlation between the partition coefficients of the biomolecules and ILs and the biomolecules octanol-water partition coefficients.

Potential of Aqueous Two-Phase Systems for the Separation of Levodopa from Similar Biomolecules.

BACKGROUND: Levodopa is a precursor of several neurotransmitters, such as dopamine, and is used in the treatment of the Parkinson's disease. In this work, an alternative strategy was studied to separate levodopa from similar biomolecules using aqueous two-phase systems (ATPS). RESULTS: Ternary ATPS composed of polyethylene glycol (PEG) 400 or ionic liquids (ILs), citrate buffer (K3C6H5O7/C6H8O7) at pH 7.0 and water, and quaternary ATPS composed of PEG 400, K3C6H5O7/C6H8O7 at pH 7.0, water and the same ILs at 5 wt%, were studied. The respective liquid-liquid phase diagrams were determined at 298 K to appraise the mixture compositions required to form two-phase systems, followed by studies of the partition of levodopa and structurally similar biomolecules (dopamine, L-phenylalanine, and L-tyrosine). Their partition coefficients and extraction efficiencies have been determined, and the selectivity of the ATPS to separate levodopa from the remaining biomolecules evaluated. CONCLUSION: The results obtained indicated that PEG-based ATPS were the most effective to separate levodopa from L-phenylalanine while the separation from the other biomolecules was better using IL-based ATPS, in particular those based on [P4444]Cl and [N4444]Cl, with extraction efficiencies of levodopa to the salt-rich phase ranging between 62.7 and 74.0%, and of the remaining biomolecules to polymer/IL-rich phase up to 91.5%.

Lipase Immobilization on Silica Xerogel Treated with Protic Ionic Liquid and its Application in Biodiesel Production from Different Oils.

Treated silica xerogel with protic ionic liquid (PIL) and bifunctional agents (glutaraldehyde and epichlorohydrin) is a novel support strategy used in the effective immobilization of lipase from Burkholderia cepacia (LBC) by covalent binding. As biocatalysts with the highest activity recovery yields, LBC immobilized by covalent binding with epichlorohydrin without (203%) and with PIL (250%), was assessed by the following the hydrolysis reaction of olive oil and characterized biochemically (Michaelis⁻Menten constant, optimum pH and temperature, and operational stability). Further, the potential transesterification activity for three substrates: sunflower, soybean, and colza oils, was also determined, achieving a conversion of ethyl esters between 70 and 98%. The supports and the immobilized lipase systems were characterized using Fourier transform infrared spectra (FTIR), scanning electron microscopy (SEM), elemental analysis, and thermogravimetric (TG) analysis.

Contact angles and wettability of ionic liquids on polar and non-polar surfaces.

Many applications involving ionic liquids (ILs) require the knowledge of their interfacial behaviour, such as wettability and adhesion. In this context, herein, two approaches were combined aiming at understanding the impact of the IL chemical structures on their wettability on both polar and non-polar surfaces, namely: (i) the experimental determination of the contact angles of a broad range of ILs (covering a wide number of anions of variable polarity, cations, and cation alkyl side chain lengths) on polar and non-polar solid substrates (glass, Al-plate, and poly-(tetrafluoroethylene) (PTFE)); and (ii) the correlation of the experimental contact angles with the cation-anion pair interaction energies generated by the Conductor-like Screening Model for Real Solvents (COSMO-RS). The combined results reveal that the hydrogen-bond basicity of ILs, and thus the IL anion, plays a major role through their wettability on both polar and non-polar surfaces. The increase of the IL hydrogen-bond accepting ability leads to an improved wettability of more polar surfaces (lower contact angles) while the opposite trend is observed on non-polar surfaces. The cation nature and alkyl side chain lengths have however a smaller impact on the wetting ability of ILs. Linear correlations were found between the experimental contact angles and the cation-anion hydrogen-bonding and cation ring energies, estimated using COSMO-RS, suggesting that these features primarily control the wetting ability of ILs. Furthermore, two-descriptor correlations are proposed here to predict the contact angles of a wide variety of ILs on glass, Al-plate, and PTFE surfaces. A new extended list is provided for the contact angles of ILs on three surfaces, which can be used as a priori information to choose appropriate ILs before a given application.

Immobilization of Candida rugosa lipase onto an eco-friendly support in the presence of ionic liquid.

Candida rugosa lipase (CRL) was immobilized on an eco-friendly support poly(3-hydroxybutyrate-co-hydroxyvalerate) (PHBV), by physical adsorption, using different ionic liquids (ILs) as immobilization additives. This was to investigate the influence of cationic core ([C4mpy]Cl, [C4min]Cl), of anions ([C4min]Cl, [C4min]N(CN)2, [C4min]Tf2N), and of cation chain length ([C2min]Tf2N, [C4min]Tf2N) in the immobilization process. The immobilized biocatalysts (IB) were characterized with respect to the morphological, physico-chemical properties, total activity recovery yield (Ya), and biochemical properties of more efficient IB were evaluated. Initially, it was found that the change of cationic core did not influence in Ya compared to the control. With change of anions, it was seen that the best result was obtained for the more hydrophobic anion (Tf2N), and finally increasing the cation chain length increased Ya. IB most efficient with [C4min]Tf2N obtained 78 % of Ya, more than twice the control value (30 %) and a considerable enhancement of operational stability compared with the control.

Aqueous Two-Phase Systems formed by Biocompatible and Biodegradable Polysaccharides and Acetonitrile.

In this work, it is shown that novel aqueous two-phase systems can be formed by the combination of acetonitrile and polysaccharides, namely dextran. Several ternary phase diagrams were determined at 25 °C for the systems composed of water + acetonitrile + dextran. The effect of the dextran molecular weight (6,000, 40,000 and 100,000 g.mol-1) was ascertained toward their ability to undergo liquid-liquid demixing. An increase in the dextran molecular weight favors the phase separation. Furthermore, the effect of temperature (25, 35 and 45 °C) was evaluated for the system constituted by the dextran of higher molecular weight. Lower temperatures are favorable for phase separation since lower amounts of dextran and acetonitrile are required for the creation of aqueous two-phase systems. In general, acetonitrile is enriched in the top phase while dextran is majorly concentrated in the bottom phase. The applicability of this new type of two-phase systems as liquid-liquid extraction approaches was also evaluated by the study of the partition behavior of a well-known antioxidant - vanillin - and used here as a model biomolecule. The optimized conditions led to an extraction efficiency of vanillin of 95% at the acetonitrile-rich phase.

Improved L-Asparaginase Properties and Reusability by Immobilization onto Functionalized Carbon Xerogels.

Enzyme immobilization can offer a range of significant advantages, including reusability, and increased selectivity, stability, and activity. In this work, a central composite design (CCD) of experiments and response surface methodology (RSM) were used to study, for the first time, the L-asparaginase (ASNase) immobilization onto functionalized carbon xerogels (CXs). The best results were achieved using CXs obtained by hydrothermal oxidation with nitric acid and subsequent heat treatment in a nitrogen flow at 600 °C (CX-OX-600). Under the optimal conditions (81 min of contact time, pH 6.2 and 0.36 g/L of ASNase), an immobilization yield (IY) of 100 % and relative recovered activity (RRA) of 103 % were achieved. The kinetic parameters obtained also indicate a 1.25-fold increase in the affinity of ASNase towards the substrate after immobilization. Moreover, the immobilized enzyme retained 97 % of its initial activity after 6 consecutive reaction cycles. All these outcomes confirm the promising properties of functionalized CXs as support for ASNase, bringing new insights into the development of an efficient and stable immobilization platform for use in the pharmaceutical industry, food industry, and biosensors.

Active Cu(II), Mn(II) and Ag(I) 1,10-phenanthroline/1,10-phenanthroline-5,6-dione/dicarboxylate chelates: effects on Scedosporium.

Background: Scedosporium/Lomentospora species are human pathogens that are resistant to almost all antifungals currently available in clinical practice. Methods: The effects of 16 1,10-phenanthroline (phen)/1,10-phenanthroline-5,6-dione/dicarboxylate chelates containing Cu(II), Mn(II) and Ag(I) against Scedosporium apiospermum, Scedosporium minutisporum, Scedosporium aurantiacum and Lomentospora prolificans were evaluated. Results: To different degrees, all of the test chelates inhibited the viability of planktonic conidial cells, displaying MICs ranging from 0.029 to 72.08 µM. Generally, Mn(II)-containing chelates were the least toxic to lung epithelial cells, particularly [Mn2(oda)(phen)4(H2O)2][Mn2(oda)(phen)4(oda)2].4H2O (MICs: 1.62-3.25 µM: selectivity indexes >64). Moreover, this manganese-based chelate reduced the biofilm biomass formation and diminished the mature biofilm viability. Conclusion: [Mn2(oda)(phen)4(H2O)2][Mn2(oda)(phen)4(oda)2].4H2O opens a new chemotherapeutic avenue for the deactivation of these emergent, multidrug-resistant filamentous fungi.

Metals have been used to treat microbial infections for centuries. In this context, the effects of 16 metal-based compounds against the human pathogens Scedosporium apiospermum, Scedosporium minutisporum, Scedosporium aurantiacum and Lomentospora prolificans were tested. All the 16 metal-based compounds were able to interfere with the viability of these fungal pathogens to different degrees. Among the 16 compounds, a manganese-containing compound presented the best activity against the fungal species and it presented the least toxicity to a human lung cell line. In addition, this manganese-containing compound reduced the ability of fungal cells to come together and form a type of community called biofilm. In conclusion, the manganese-containing compound presents a promising option against the multidrug-resistant filamentous fungi species belonging to the Scedosporium/Lomentospora genera.