The assessment of drug taste is crucial for pediatric treatments so that formulations can be developed to enhance their effectiveness. In this study,
in vivo
and in vitro methods were applied to ...evaluate the taste of tablets of three drugs administered to children without taste-masking excipients to treat tropical diseases, namely artesunate-mefloquine (ASMQ), praziquantel (PZQ), and benznidazole (BNZ). In the first method, a model of rat palatability was adapted with recirculation to ensure sample dispersion, and the data were analyzed using ANOVA (single factor, 95%). The taste assessment results (
in vivo
) indicated an aversion to the three medicines, denoted by the animals retracting themselves to the bottom of the box after the first contact with the drugs. For the placebo samples, the animals behaved normally, indicating that taste perception was acceptable. The second method was based on the
in vitro
analysis of capacitance data from a homemade impedimetric electronic tongue. Consistent with the
in vivo
taste assessment results, the data points obtained with PZQ, ASMQ, and BNZ were far away from those of their placebos in a map built with the multidimensional projection technique referred to as Interactive Document Mapping (IDMAP). A combined analysis of the results with the two methods allowed us to confirm the bitterness of the three drugs, also pointing to electronic tongues as a promising tool to replace
in vivo
palatability tests.
Graphical abstract
Understanding the different scales of temporal variability is crucial to improve the knowledge of the biogeochemical processes in the land-ocean interface. In this study, we evaluated the role of ...continental runoff and intrusion of oceanic water masses in the trophic state of the Bay of Santa Catarina Island (BSCI) over the last three decades (1993–2019) by using multiple biogeochemical and eutrophication assessment tools. The sub-watersheds of BSCI showed high concentrations of nutrients, fecal coliform and chlorophyll-a, directly correlated to the number of inhabitants. Worst-case scenarios were found in summer and fall seasons due to sewage inputs caused by mass tourism and the inefficiency or even absence of treatment systems, boosted by strong rainfall. The intrusion of the South Atlantic Central Water and the Plata Plume Water into the BSCI favored autotrophy in the summer and heterotrophy in the winter, coupled with low and high residence time, respectively. El Niño events enhanced rainfall and continental runoff, exporting elevated nutrients and phytoplankton biomass loads from the eutrophic rivers to the continental shelf. The pattern reverses during La Niña, when chlorophyll and nutrient peaks were detected inside the bay. Eutrophication evaluation indicated that the trophic state oscillated from moderate to high and that these conditions tend to remain the same in future scenarios due to the moderate residence time of the water, anthropogenic pressures, periodic algal blooms and the intrusion of nutrient-rich oceanic water masses. Management actions, such as the improvement of the wastewater treatment system and wetlands restoration, are needed in order to mitigate eutrophication and the loss of ecosystem services and functions.
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•A subtropical bay is under eutrophication pressure due to sewage discharge.•Meteo-oceanographic patterns shifted residence time and the ecosystem metabolism.•Autotrophic conditions predominate in the summer and heterotrophic in the winter.•El Niño and La Niña events modulate physical and biogeochemical processes.•Assessment models indicated that the eutrophic conditions will persist.
The present work aims to provide the basic characterization of sol–gel immobilized inulinase, a biocatalyst configuration yet unexploited, using as model system the hydrolysis of inulin to fructose. ...Porous xerogel particles with dimensions in slight excess of 10 μm were obtained, yielding an immobilization efficiency of roughly 80%. The temperature– and pH–activity profiles displayed a broader bell-shaped pattern as a result of immobilization. In the latter case, a shift of the optimal pH of 0.5 pH units was observed towards a less acidic environment. The kinetic parameters estimated from the typical Michaelis–Menten kinetics suggest that immobilization in sol–gel did not tamper with the native enzyme conformation, but on the other hand, entrapment brought along mass transfer limitations. The sol–gel biocatalyst displayed a promising operational stability, since it was used in more than 20 consecutive 24-hour batch runs without noticeable decay in product yield. The performance of sol–gel biocatalyst particles doped with magnetite roughly matched the performance of simple sol–gel particles in a single batch run. However, the operational stability of the former proved poorer, since activity decay was evident after four consecutive 24-hour batch runs.
The lipase catalyzed hydrolysis of tricaprylin in miniemulsion is monitored with NMR and HPLC. The product composition is determined by the choice of the enzyme and the reaction time. Polyurethane is ...directly prepared from the hydrolysis products.
•Efficient lipase catalyzed hydrolysis and glycerolysis of tricaprylin in miniemulsion.•Conversion to mono and diglycerides is monitored by HPLC and NMR.•Lipase PS exhibits preference for reaction in sn-2 position.•Polyurethane can be prepared from the hydrolysis products without workup.
Miniemulsion droplets are used as the reaction environment for the enzyme catalyzed hydrolysis and glycerolysis of tricaprylin. The reaction was conducted at slightly elevated temperatures in aqueous dispersion without any organic solvent. Lipase PS from Pseudomonas cepacia, known as a lipase without site preference (unspecific), and lipase from Rhizopus arrhizus (RAL), a lipase with sn-1,3 preference, were used for the reactions. The time courses of the conversions were studied in detail with NMR and HPLC. RAL exhibited sn-1,3 preference and Lipase PS clearly showed significant reaction in sn-2 position during hydrolysis of the triglyceride as well as during glycerolysis. From the hydrolysis products, polyurethane-based polymers were synthesized by directly adding isophoronediisocyanate to the miniemulsions after different reaction times. The properties of the products, e.g. the Tg, can be controlled by time-dependent addition of the isocyanate.
Bio-Flex® is a commercial blend of poly(lactic acid) (PLA) and poly(butylene adipate-co-terephthalate) (PBAT) used in several industrial and daily applications. To understand the degradation behavior ...of this mixture, two laboratory tests were conducted, one simulating outdoor accelerated weathering (OAW) and the other mimicking degradation in marine environments in seawater (MES). To increase its degradability, Bio-Flex was mixed with various additives such as chloroacetic acids - trichloroacetic acid (TCA) and dichloroacetic acid (DCA) - and esters of the latter. The samples were characterized before and after the degradation tests by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and mechanical properties. Size exclusion chromatography (SEC) and contact angle were also evaluated. The acids were found to be very effective in degrading PLA/PBAT blends, even during the blending process. It follows that the esters of DCA are suitable as good additives to increase the degradation ratio of the PLA/PBAT blend when an enhanced degradation process is required.
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•Chloroacetic acids could be used to increase PLA/PBAT blends degradability.•Weathering exposure degrades polymers quickly than marine environments.•Amorphous phase is degraded in a preferential way than crystalline phase.•Esters of dichloroacetic acid are effective in increasing degradability too.
The lipase from
Rhizopus niveus
(RNL) catalyzed by unspecific protein catalysis the aldol reactions between cyclohexanone and aromatic aldehydes in organic solvents with water or aqueous buffer ...solution. The reactional conditions strongly influenced the yield (0–99%) and enantioselectivities in the
anti
-products (6–55%
ee
anti
). The aldol products with enantioselectivities in the
anti
-product were observed for inactive enzyme and in denaturing conditions. Therefore, the reactions in the evaluated conditions proceeded by unspecific protein catalysis with moderate enantioselectivities and not by promiscuous activity. These enzymatic studies identify a new green catalyst for aldol reactions and new possibilities for lipases, especially for the use of the lipase RNL, which has been scarcely reported in the literature and catalyzed the aldol reaction between different aromatic aldehydes and cyclohexanone.
Graphical Abstract
•A non-isothermal kinetic study, using experiments carried out in batch stirred reactor, has been made for the enzymatic synthesis of ethyl caproate by Fusrium solani pisi cutinase.•The main kinetic ...characteristic was found to follow a 3rd ordered Ping Pong Bi Bi mechanism.•The model shows that productivity decreases as the temperature increases, which means that lower temperatures favour the reaction esterification.
The present work aims to achieve additional insight on a mechanism describing the fundamental steps involved in the esterification reactions catalyzed by cutinase. The synthesis of ethyl caproate has been used as a model system to obtain a suitable kinetic model to estimate the activation energies involved in the various steps of the reaction pathway.
Kinetic measurements have been made for the enzymatic esterification of caproic acid with ethyl alcohol catalyzed by recombinant Fusarium solani pisi cutinase expressed in Saccharomyces cerevisiae SU50. Different temperature conditions, from 25 to 50°C, were tested for two different alcohol/acid molar ratios (R=1 and R=2). The third ordered Ping Pong Bi Bi mechanism with alcohol inhibition was shown to be able to describe the experimental results. The model shows that the productivity decreases as the reaction temperature increases.
The present work focuses on the development and basic characterization of a new magnetic biocatalyst, namely penicillin G acylase (PGA), immobilized in sol‐gel matrices with magnetic properties, ...ultimately aimed for application in cephalexin (CEX) synthesis. A mechanically stable carrier, based on porous xerogels silica matrixes starting from tetramethoxysilane (TMOS), was prepared leading to micro‐carriers with medium sized particles of 30 μm, as determined by scanning electron microscopy. An immobilization yield of 95–100% and a recovered activity of 50–65% at 37°C, as determined by penicillin G (PG) hydrolysis (pH STAT method), were observed. These results clearly exceed those reported in a previous work on PGA immobilization in sol‐gel, where only 10% of activity was recovered. The values of activity were kept constant for 6 months. Immobilized PGA (682 U/gdry weight) retained high specific activity throughout ten consecutive runs for PG hydrolysis, suggesting adequate biocatalyst stability. The CEX synthesis was performed at 14°C, using the free and immobilized PGA in aqueous medium. Phenylglycine methyl ester was used as acyl donor at 90 mM and 7‐aminodeacetoxycephalosporanic acid was the limiting substrate at 30 mM. The CEX stoichiometric yield after 1‐h reaction was close to 68% (23 mM CEX/h) and 65% (19 mM CEX/h), respectively.
Ultrasound (US)-assisted extraction has been widely used for metal ion extraction in plants due to its unique properties of decreased extraction time, minimal contamination, low reagent consumption ...and low cost. However, very few papers present a sound comparison between probe-focussed sonication and conventional stirring in the evaluation of metal ion extraction in plants. In this study, ultrasonic-assisted digestion has been evaluated and compared to magnetic stirring for total copper and cadmium determination by atomic absorption spectrometry in biological samples (plants, plankton and mussels). The same experimental conditions of sample amount and particle size, extractant solution and extraction time were applied for both ultrasound and magnetic stirring-assisted extraction methods in order to truly compare their effect on metal ion solubilisation. To gain further insight in this issue, dried and fresh plants were tested. The results obtained indicated that osmotic tension in cell walls, produced when dried and powdered samples were immersed in the extractant solution, had an important contribution to metal ion solubilisation, the enhancement due to US for the same purpose being negligible. graphic removed
Here, we report a new two-step enzymatic polymerization strategy for the synthesis of poly(octamethylene suberate) (POS) using an immobilized Pseudozyma antarctica lipase B (IMM-PBLI). The strategy ...overcomes the lack of enzymatic POS synthesis in solvent-free systems and increases the final polymer molecular weight. In the first step, the direct polycondensation of suberic acid and 1,8-octanediol was catalyzed by IMM-PBLI at 45 °C, leading to the production of prepolymers with molecular weights (MWs) of 2800, 3400, and 4900 g mol−1 after 8 h in miniemulsion, water, and an organic solvent (cyclohexane: tetrahydrofuran 5:1 v/v), respectively. In the second polymerization step, wet prepolymers were incubated at 60 or 80 °C, at atmospheric pressure, in the presence of IMM-PBLI, and without stirring. The final POS polymers showed a significant increase in MW to 5000, 5800, and 19,800 g mol−1 (previously synthesized in miniemulsion, water, or organic solvent, respectively). FTIR analysis of the final polymers confirmed the successful POS synthesis and a high degree of monomer conversion. This innovative two-step polymerization strategy opens up a new opportunity for implementing greener and more environmentally friendly processes for synthesizing biodegradable polyesters.
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