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.
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.
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
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.
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.
The cold sintering process was applied as a suitable method to produce high relative density (> 90%) ZnO/MoS.sub.2 nanocomposite. The cold sintering process was done at 170 °C, 480 MPa for 45 min to ...fabricate ZnO/MoS.sub.2 nanocomposite in a bulk form containing 1-5% MoS.sub.2. In addition to examining the effective parameters of the process, the proper solvents in cold sintering of ZnO/MoS.sub.2 nanocomposite were investigated. The XRD, FTIR, and RAMAN results affirmed the removal of added solvent and the absence of any secondary phase or unknown component in the cold-sintered ZnO/MoS.sub.2 nanocomposite. The SEM and EDX results illustrated that to improve the MoS.sub.2 nanoparticle homogeneous distribution through the ZnO powders, a new three-component solvent (acetic acid-DMSO-water) with enhanced viscosity should be exerted. Increasing MoS.sub.2 nanoparticles resulted in a slight reduction in the final density of the nanocomposite as 5% MoS.sub.2 decreased the relative density from 95.2 to 90.9%. The TGA/DTA curves proved that the thermal stability of the fabricated nanocomposite was up to 450 °C. Alongside the bulk form of the produced nanocomposite, UV-visible investigations illustrated that the MoS.sub.2 nanoparticles enhanced the ZnO substrate's visible light absorption, indicating the potential of the cold-sintered ZnO/MoS.sub.2 nanocomposite for development in optical applications.
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