Starch is a biocompatible and economical biopolymer in which interest has been shown in obtaining electrospun fibers. This research reports that cassava (CEX) and pea (PEX) starches pretreated by ...means of reactive extrusion (REX) improved the starches rheological properties and the availability of amylose to obtain fibers. Solutions of CEX and PEX (30-36% w/v) in 38% v/v formic acid were prepared and the rheological properties and electrospinability were studied. The rheological values indicated that to obtain continuous fibers without beads, the entanglement concentration (Ce) must be 1.20 and 1.25 times the concentration of CEX and PEX, respectively. In CEX, a higher amylose content and lower viscosity were obtained than in PEX, which resulted in a greater range of concentrations (32-36% w/v) to obtain continuous fibers without beads with average diameters ranging from 316 ± 65 nm to 394 ± 102 nm. In PEX, continuous fibers without beads were obtained only at 34% w/v with an average diameter of 170 ± 49 nm. This study showed that starches (20-35% amylose) pretreated through REX exhibited electrospinning properties to obtain fibers, opening the opportunity to expand their use in food, environmental, biosensor, and biomedical applications, as vehicles for the administration of bioactive compounds.
A new process for the production of formic acid from corncob waste was constructed by using MnCeOx/Nb2O5 catalyst. Among pristine hemicellulose, cellulose or lignin in corncob, hemicellulose gave the ...maximum formic acid yield (61.2 %). Dilute hydrochloric acid (0.37 wt%) assisted-ball milling pretreatment of pristine cellulose reduced its crystallinity and increased formic acid yield from 2.6 % to 40.2 %, while lignin was hardly converted into formic acid (<7 %). In the assessment of Mn and Ce in MnCeOx/Nb2O5, a synergistic effect was observed in formic acid formation. Formic acid yield obtained over Mn6Ce4Ox/Nb2O5 was 1.5-fold higher that obtained over MnOx/Nb2O5. Formic acid yield as high as 0.56 g/g could be obtained directly from pretreated corncob, demonstrating potential for converting agro-waste biomass into formic acid over Mn6Ce4Ox/Nb2O5 catalyst. Mechanistic studies revealed that arabinose, glyceric acid and glycolic acid were main intermediates in the conversion of corncob to formic acid.
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•Synergistic effect in MnCeOx/Nb2O5 promoted the biomass oxidation to formic acid.•Corncob pretreated with acid-assisted ball milling give 0.56 g/g formic acid yield.•Arabinose and glyceric acid were main intermediates for corncob to formic acid.
Oxidized cotton cellulose with COOH contents of 16.0-24.0%, meeting USP requirements, was produced in the HNO.sub.3-H.sub.3PO.sub.4-NaNO.sub.2 system. This allowed it to be used as a biodegradable ...hemostatic agent. The structures of oxidized cotton celluloses were confirmed using IR spectroscopy and elemental analysis and were studied using X-ray diffraction structure analysis. Diffraction patterns of celluloses oxidized for 4-24 h had reflections characteristic of two polymorphic modifications, i.e., cellulose I (characteristic of starting cotton cellulose) and cellulose II.
Keywords DPPH; IC.sub.50 correction; Stoichiometry; Mathematical model Highlights * IC.sub.50 has been reported with misconceptions in a large number of studies. * Attention is drawn to the correct ...choice of the units when reporting the IC.sub.50. * Both molecular and radical form of DPPH contribute in UV--Vis analysis. * A mathematical model is presented in order to improve the DPPH.sup.* determination. The DPPH method has been reported with misconceptions in a large number of studies, thus precluding comparison of results. Attention is drawn to a common mistake in the unit used to express the IC.sub.50 of ascorbic acid and other antioxidant substances. Concentration of the antioxidant is widely misused with a total disregard for the DPPH.sup.* concentration, while the molar ratio of antioxidant/DPPH.sup.* would be the correct choice. Data from 26 studies with widely varying IC.sub.50 values were renormalized according to reaction stoichiometry, resulting in values which are more coherent and closer to the ideal one of 0.25 for at least 15 of them. In addition, the model which is currently being used to calculate the DPPH.sup.* concentration can lead to an overestimation of around 7%, as it does not take into account the small contribution of the reaction product. In view of that, we present a mathematical model to correct the overestimation of the DPPH.sup.* concentration. Author Affiliation: (a) Federal University of Santa Maria - UFSM, Department of Chemistry, Av. Roraima, 1000, 97105-900, Santa Maria, RS, Brazil (b) Federal University of Santa Maria - UFSM, Department of Physics, Av. Roraima, 1000, 97105-900, Santa Maria, RS, Brazil * Corresponding author. Article History: Received 5 October 2020; Revised 4 March 2021; Accepted 7 March 2021 Byline: Bryan Brummelhaus de Menezes (a), Lucas Mironuk Frescura (a), Rafael Duarte (a), Marcos Antonio Villetti (b), Marcelo Barcellos da Rosa marcelo.b.rosa@ufsm.br (a,*)
Aliphatic alcohols (AAs), including terpenoic alcohols (TAs), are ubiquitous in the atmosphere due to their widespread emissions from natural and anthropogenic sources. Hydroxyl radical (OH) is the ...most important atmospheric oxidant in both aqueous and gas phases. Consequently, the aqueous oxidation of the TAs by the OH inside clouds and fogs is a potential source of aqueous secondary organic aerosols (.sub.aq SOAs). However, the kinetic data, necessary for estimating the timescales of such reactions, remain limited. Here, bimolecular rate coefficients (kOHaq) for the aqueous oxidation of 29 C.sub.2 -C.sub.10 AAs by hydroxyl radicals (OH) were measured with the relative rate technique in the temperature range 278-328 K. The values of kOHaq for the 15 AAs studied in this work were measured for the first time after validating the experimental approach. The kOHaq values measured for the C.sub.2 -C.sub.10 AAs at 298 K ranged from 1.80 x 10.sup.9 to 6.5 x 10.sup.9 M.sup.-1 s.sup.-1 . The values of activation parameters, activation energy (7-17 kJ mol.sup.-1 ), and average Gibbs free energy of activation (18 ± 2 kJ mol.sup.-1) strongly indicated the predominance of the H-atom abstraction mechanism. The estimated rates of the complete diffusion-limited reactions revealed up to 44 % diffusion contribution for the C.sub.8 -C.sub.10 AAs.
A highly sensitive colorimetric sensing strategy based on enzyme@metal-organic framework (GAA@Cu-MOF) and IrO.sub.2/MnO.sub.2 nanocomposite was exploited innovatively for screening of ...alpha-glucosidase (GAA) inhibitors. IrO.sub.2/MnO.sub.2 nanocomposite exhibits excellent oxidase-mimicking activity which can directly catalyze the oxidation of 3,3.sup.,5,5.sup.,-tetramethylbenzidine (TMB) into a blue product with an absorption maximum at 652 nm. And GAA@Cu-MOF can decompose L-ascorbic acid-2-O-alpha-D-glucopyranosyl (AAG) to ascorbic acid (AA). The produced AA can destroy the IrO.sub.2/MnO.sub.2 nanocomposite and reduce its oxidase-like activity. However, the generation of AA is restricted when GAA inhibitors are added to the system, which allows the oxidase-like activity of the IrO.sub.2/MnO.sub.2 nanocomposite to be maintained. In view of this, a method for screening of GAA inhibitors was developed. In addition to enhancing the stability of GAA, the method can also effectively avoid the potential interference of H.sub.2O.sub.2 in the screening process of GAA inhibitors, which helps to improve the sensitivity of the method. Therefore, highly sensitive determination for acarbose and ascorbic acid are achieved with detection limits of 6.27 nM and 1.23 muM, respectively. The proposed method was successfully applied to screen potential GAA inhibitors from oleanolic acid derivatives.
As natural metabolites, organic acids have been widely applied in food, pharmaceutical, and bio-based materials industries. Particularly, the short-chain organic acids, including C2, C3, C4, C5, and ...C6 organic acids, are necessary intermediate metabolites in cells and are also alternatives to some commercial chemical products. As the necessary metabolites in cells, most major short-chain organic acids can be produced through microbial fermentation. Specifically, with the development of synthetic biology, metabolic engineering could endow cells with the ability to produce more short-chain organic acid products including propionic acid, pyruvate, lactic acid, 3-hydroxypropionic acid, malic acid, succinic acid, fumaric acid, butyric acid, itaconic acid, α-ketoglutaric acid, glutaric acid, citric acid, gluconic acid, muconic acid, adipic acid, xylonic acid, and so on. The recent advances in the biological production of short-chain organic acids, as well as the challenges and perspectives, are summarized in this review to promote the generation of microbial cell factories for the production of short-chain organic acids.
Key points
• Outlines the production strategy of short-chain organic acids
• Provide guidance for efficient synthesis of short-chain organic acids
• Impacts the necessary factor of acid resistance on the successful production of host cells
Amaranth is a nutritionally valuable crop, as it contains phenolic acids and flavonoids, yielding diverse plant secondary metabolites (PSMs) like phytosterol, tocopherols, and carotenoids. This study ...explored the variations in the contents of seventeen polyphenolic compounds within the leaves of one hundred twenty Amaranthus accessions representing nine Amaranthus species. The investigation entailed the analysis of phenolic content across nine Amaranthus species, specifically A. hypochondriacus, A. cruentus, A. caudatus, A. tricolor, A. dubius, A. blitum, A. crispus, A. hybridus, and A. viridis, utilizing ultra performance liquid chromatography with photodiode array detection (UPLC-PDA). The results revealed significant differences in polyphenolic compounds among accessions in which rutin content was predominant in all Amaranthus species in both 2018 and 2019. Among the nine Amaranthus species, the rutin content ranged from 95.72 ± 199.17 μg gsup.−1 (A. dubius) to 1485.09 ± 679.51 μg gsup.−1 (A. viridis) in 2018 and from 821.59 ± 709.95 μg gsup.−1 (A. tricolor) to 3166.52 ± 1317.38 μg gsup.−1 (A. hypochondriacus) in 2019. Correlation analysis revealed, significant positive correlations between rutin and kaempferol-3-O-β-rutinoside (r = 0.93), benzoic acid and ferulic acid (r = 0.76), and benzoic acid and kaempferol-3-O-β-rutinoside (r = 0.76), whereas gallic acid showed consistently negative correlations with each of the 16 phenolic compounds. Wide variations were identified among accessions and between plants grown in the two years. The nine species and one hundred twenty Amaranthus accessions were clustered into six groups based on their seventeen phenolic compounds in each year. These findings contribute to expanding our understanding of the phytochemical traits of accessions within nine Amaranthus species, which serve as valuable resources for Amaranthus component breeding and functional material development.
A turn-on method for determining alpha-glucosidase activity is described using a chemical redox strategy in which the fluorescence of red fluorescent carbon dots (CDs) is modulated. The red ...fluorescent CDs were prepared using a solvothermal method with p-phenylenediamine and sodium citrate. The excitation and emission maxima of the CDs were 490 and 618 nm, respectively. Ce.sup.4+ ions catalyze the oxidation of the colorless substrate 3,3',5,5'-tetramethylbenzidine (TMB) to give a blue oxidized TMB product (oxTMB). Absorption by oxTMB overlaps with the red light emitted by the CDs because of the fluorescence inner filter effect; therefore the presence of oxTMB decreases the intensity of fluorescence emission by the CDs. However, hydrolysis of L-ascorbic acid-2-O-alpha-D-glucopyranosyl by the enzyme alpha-glucosidase causes formation of ascorbic acid . Ascorbic acid reduces oxTMB to TMB, so that the inner filter effect disappeared and the fluorescence recovered. The strategy allows alpha-glucosidase activity to be successfully determined down to 0.02 U mL.sup.-1 and gives a dynamic linear range of 0-5.5 U mL.sup.-1. The strategy is very selective for alpha-glucosidase activity in the presence of potentially interfering substances. The method has been successfully applied to the determination of alpha-glucosidase activity in spiked human serum samples and gave satisfactory results.
Beekeepers can use a variety of treatments against Varroa destructor, the parasitic mite of Apis mellifera. However, sustainable and easy-to-use solutions are still scarce, considering the complexity ...of reaching the parasite alone. Current treatments involve soft acaricides, although their mechanism of action is not well understood. We investigated the effects of organic acids such as tartaric, lactic, formic, and citric acids on the attachment abilities of V. destructor under laboratory conditions. Preventing parasites from gripping or holding on to their hosts is a crucial target for mite control strategies. We challenged grip skills through the Rotavar setup after the direct application of acids to mites’ arolia. We also tested the potential for mites to fall off honeybees after bee treatment. We found that tartaric, citric, and lactic acids were good candidates to impair the attachment of V. destructor twenty-four hours post-treatment. However, lactic acid remained the only candidate at a reasonable concentration to destabilise mites after the honey bee’s treatment without reducing their lifespan. While we conducted these experiments under artificial conditions, our results improved our comprehension of the organic acids’ potential impact on V. destructor. They can also help with the development of new methods for hive application for beekeepers worldwide.
