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Streamlining Scanning Electron Microscopy (SEM) Sample Preparation Protocols for Analyzing the Mechanisms of Heavy Metal Bioremediation by Microalgae
No full textMicroalge are shown to be a promising solution for phytoremediation of metal-polluted aquatic sites through several mechanisms [1], such as metal binding to the cell wall and/or the
formation of excreted polymers (mucilage) [2]. This way microalgae cells mitigate metal toxicity through the formation of metal complexes with polysaccharides that allow the gradual intake
of metals as a part of both physiological and adaptive response (buffering) [3]. Herein, we used
SEM to examine the morphological response of metabolically active green cell type of Haematococcus pluvialis (microzooids) to high manganese (Mn) concentrations exceeding their
physiological quota. The aim was to optimize the fixation protocol that preserves the mucilage
and other extracellular secreted cell- associated materials and maintains structural changes in the
outer cell wall architecture. After the initialuse of glutaraldehyde for fixation, we applied two
different dehydration mixtures (graded concentrations of ethanol-water or acetic acid-ethanol
mixtures). Acetic acid and ethanol are routinelyused for histological specimen fixation, while
the former allows dehydration without detrimental effects [4]. Both dehydration mixtures gave
equal results with control cells (Fig 1A). Our SEM analysis revealed granular deposits on microzooid surfaces after 1 hour of the treatment using ethanol-water solution (Fig 1B) for gradual
dehydration while such response was mainly omitted using an acetic acid-ethanol mixture (Fig
1C). The size and surface of these cells have changed from mainly smooth to more shrunken
with a considerably wrinkled surface in both cases compared to the control. These results indicate the possible presence of acid-soluble polysaccharides in mucilage, similar to the pectin from
marine macroalgae species [5] which in the presence of acid converts from the insoluble form
of protopectin to the water-soluble form [6]. Ethanol proved to be the solvent of choice for this
kind of sample dehydration since it reduces the degradation of biomolecules present in samples
[7], but one must proceed with caution as excessive cell shrinkage remains a potential issue. [8
The Effects of Hydrogel Type on The Kinetics of Dehydration Process
No full textHydrogels are prominent materials with smart response to external stimuli, swelling ability, biocompatibility, etc. Dehydration of hydrogels, as a complex reversible and endothermic physicochemical process of removing water from material, which takes place under conditions of simulated energy exchange and mass transfer, is of remarkable practical and theoretical importance, because hydrogels could be assumed as model systems suitable for modeling the kinetics of dehydration of living tissues and foods. Our investigation is aimed to get insight into the effect of hydrogel type on the applicability of novel kinetic models that can describe hydrogel dehydration precisely and with a higher degree of reliability: Vyzovkin’s isoconversion method, Webull’s distribution of reaction times, distribution apparent energy activation model, logistic function, etc. We used hydrogels based on poly(acrylic acid), poly(methacrylic acid), alginate and gelatin. All hydrogels were synthesized in our laboratory, equilibrium swollen in distilled water and their non-isothermal (heating rates 5-30 Kmin−1) and iso-thermal dehydration (293K-360K) were recorded by thermogravimetric measurement, under N2 atmosphere. Kinetics parameters: rate constants (k), activation energy (Ea), preexponential factor (lnA), and dependences of Ea and lnA on the degree of dehydration (α) were determined. The kinetic’s complexity of dehydration processes was discussed based on the dependences of Ea and lnA on α. The correlations among the values of k, Ea and lnA with the xerogels’ structural properties were determined. The complex nature of hydrogels’ dehydration kinetics was revealed and explained as the consequence of phase state of the absorbed water, fluctuating structure and thermal activation of the hydrogel
From Waste to Taste: Characterization and Investigation of the Prebiotic Effect of Sunflower Meal Extract on Gut Microbiota Residents
No full textAbstract:
Sunflower meal, a by-product of sunflower oil production, contains various bioactive compounds
that can be extracted to yield high-value fractions with significant market potential. Among
these plant-based active compounds are polyphenols, which are regarded as novel prebiotics
due to their biological activities, including anti-inflammatory, antimicrobial, and antioxidant
properties, as well as their ability to modify gut microbiota. In order to utilize the potential of
the sunflower meal, a three-stage extraction with 70% ethanol (v/v) was performed, and a
polyphenolic extract yield of 17.0±0.75% was obtained. After that, a detailed characterization of
the extract was carried out in terms of total sugars, polyphenols, flavonoids, flavonols, tannins
and phenolic acids content determination, furthermore, the antioxidant properties were also
tested. In addition to significant amounts of structurally different total polyphenols (125.0 mg
GAE/g DM), the presence of phenolic acids prevails in the extract of which chlorogenic acid
is dominant. The antioxidant capacity was quantified by different methods (DPPH, CUPRAC,
ABTS and FRAP), and the obtained data lead to the conclusion that the sunflower meal
extract represents a significant source of antioxidants. Taking into account that agri-food
waste represents exceptional sources of valuable compounds, for potential application in
the development of functional food, its prebiotic effect on individual gut members was also
investigated. A wide range of concentrations of polyphenolic extract was tested on the growth
of probiotic cultures Lactobacillus plantarum, Lactobacillus rhamnosus and Saccharomyces
boulardii as well as pathogenic culture Escherichia coli. The obtained results indicate the
exceptional ability of the extract in the manipulation of intestinal microbiota which is reflected
through the proliferation of probiotic and suppression of the pathogen one. Overall, transforming
sunflower meal into a polyphenolic extract not only adds value to this agricultural by-product
but also provides a natural source of antioxidants and prebiotics, which can be leveraged in
the food industry to enhance health benefits of consumers
Regulation of surface properties and structural defects of graphitic carbon nitride via oxygen doping and plasma treatment
No full textGraphitic carbon nitride (CN) is gaining attraction as a photocatalyst for Cr(VI) reduction, thanks to its stability in acidic environment, facile preparation, low precursor cost, and moderate band gap (~2.7 eV). Still, its performance is limited primarily by inefficient separation of photogenerated electrons and holes. Recent studies show that introducing defects into CN structure can enhance its photocatalytic and photoelectric properties. The Dielectric Barrier Discharge (DBD) plasma process is emerging as an effective method to create defects in the form of oxygen-containing functional groups, which can act as electron-withdrawing sites, reducing charge carrier recombination, thus improving photocatalytic activity. Additionally, increasing oxygen content by doping, can facilitate the incorporation of more oxygen-based functional groups, like carboxyl, carbonyl, and hydroxyl. In this work, oxalic acid was used to synthesize O-doped CN, while the DBD plasma was employed to further modify the CN based samples.
The properties of the photocatalysts were studied by XRD, FTIR, FESEM, EDS, PL and DRS analysis, as well as by determination of the number of acidic surface functional groups. Photocatalytic reduction of Cr(VI) was tested at pH=3, under the simulated visible irradiation. It was shown that the primary framework of CN did not change during both doping and plasma treatment, while the content acidic groups was significantly increased, and the recombination and band gap were decreased, but the photocatalytic efficiency was not improved significantly
Optimizing Green Extraction Methods for Maximizing the Biological Potential of Dandelion, Milk Thistle, and Chamomile Seed Extracts
No full textThis study investigates the underutilized potential of agri-crops from the Asteraceae family by employing sustainable and green technologies (supercritical fluid, ultrasound, and Soxhlet extractions) to enhance the recovery of bioactive compounds. A total of 21 extracts from native and waste seeds of dandelion, milk thistle, and chamomile were systematically compared utilizing a combination of solvents (supercritical CO2 and absolute or aqueous ethanol). Supercritical CO2 extraction yielded up to 281 mg/g of oils from native seeds, while conventional techniques with ethanol recovered an additional 142 mg/g of extracts from waste seeds. Notably, waste seed extracts exhibited superior biological activity, including potent antioxidant properties (IC50 values as low as 0.3 mg/mL in the DPPH assay) and broad-spectrum antimicrobial activity against 32 microbial strains, including methicillin-resistant Staphylococcus aureus, Gram-negative bacteria, and yeast strains. Phenolic compounds were abundant, with up to 2126 mg GAE/g, alongside 25.9 mg QE/g flavonoids, and 805.5 mg/kg chlorophyll A. A selective anticancer activity of waste milk thistle extracts was observed, with a selectivity index of 1.9 to 2.7. The oils recovered from native seeds demonstrated lower bioactivity and are well-suited for applications in food. The potent bioactivity of the smaller quantities of waste seed extracts positions them as valuable candidates for pharmaceutical use
Correlation Between Morphology and Crystal Structure of Electrolytically Produced Zinc Dendritic Particles
No full textThe correlation between the morphology and crystal structure of zinc dendritic particles produced by electrolysis from the alkaline electrolyte has been established. Morphology and crystal structure of Zn particles electrodeposited by the potentiostatic regime of electrolysis at overpotentials inside (−100 and −160 mV) and outside (−220, −280, and −340 mV) the plateau of the limiting diffusion current density were characterized by scanning electron microscope (SEM) and by X-ray diffraction (XRD), respectively. The particle size distribution (PSD) was performed in order to determine the dependency of the size of dendritic particles on applied electrolysis overpotential. With increasing the overpotential of electrolysis, the shape of particles changed from irregular forms denoted as precursors of dendrites to various forms of dendrites, while the size of the particles simultaneously decreased. All types of Zn dendrites exhibited the strong (002) preferred orientation, while the precursors of dendrites exhibited (101)(002) preferred orientation. The development of strong (002) preferred orientation was explained and discussed by making an analogy with the electrolytic production of lead dendrites from the concentrated nitrate electrolyte. Although zinc and lead belong to different types of crystal lattice (Pb-face-centered cubic type and Zn-hexagonal close-packed type), they have a common characteristic that is manifested by the strong preferred orientation in the crystal plane with the lowest surface energy
Alkali-activated fly ash: a sustainable adsorbent for yttrium removal from water
No full textGiven the substantial waste produced by coal combustion in thermal power plants, including bottom
ash and fly ash, it's imperative to explore novel applications for these by-products. In order to
improve the adsorption characteristics of fly ash, chemical modification of fly ash was applied.
Unmodified and modified materials were used as adsorbents for yttrium removal from water.
Obtained samples were characterized using Fourier transform infrared spectroscopy and scanning
electron microscopy. The effect of the initial pH value and concentration of the yttrium solution, as
well as contact time on adsorption were examined. It was found that the adsorption of yttrium
follows a pseudo-second order kinetic model, while the Freundlich adsorption isotherm best
describes the adsorption process in equilibrium. Obtained results demonstrated that alkali-activated
fly ash can be used as a highly effective adsorbent for the removal of yttrium from aqueous
solutions
From the chokeberry fruit products and by-products to health-promoting effects through multifaceted in vitro bioactivity evaluation and molecular docking studies
No full textBACKGROUND: Polyphenolic-rich chokeberry extracts and juice could provide health benefits in humans. Moreover, by-products after processing stand out as a potential new source of valuable compounds. OBJECTIVE: The research aimed to evaluate in vitro bioactivity of chokeberry fruit extract, juice, and waste extract (material remaining after juice processing) based on their chemical composition and molecular docking analysis. METHODS: Spectrophotometric methods were used to determine the phenolics, anthocyanins, flavonoids, and proanthocyanins content in freeze-dried samples. Additionally, individual anthocyanins, flavonoids, and sugars were identified through HPLC analysis. The antioxidant capacity was tested using two in vitro methods and assessing antimicrobial activity. The effects of tyrosinase and acetylcholinesterase inhibition were examined using spectrophotometric methods. Molecular docking analysis identified the interaction of chokeberry components with the active sites of these enzymes. RESULTS: The waste extract exhibited the most robust antioxidant activity within the DPPH system. While bactericidal activity was absent across all chokeberry preparations, they demonstrated inhibitory effects on specific microbiological strains relevant to the gastrointestinal tract. Results revealed the chokeberry products' ability to inhibit tyrosinase and acetylcholinesterase. Molecular docking confirmed the strong interactions between chokeberry compounds and these enzymes. CONCLUSION: The results indicate the potential of chokeberry products and by-products as valuable resources for pharmaceutical applications
Phyllosilicate-based adsorbents decorated with iron oxyhydroxides: application for lead, chromates and selenites removal
No full textExpanded vermiculite (EVer) was acid activated and silanized in order to obtain suitable substrate’s surface for decoration with iron oxyhydroxides (IO). Obtained activated sample (EVa), was decorated by deposition of either prevailing goethite or amorphous iron oxyhydroxides (AIO) resulting in EV-A and EV-B adsorbent, respectively. Modifications of EVa showed improved adsorption performances when used as adsorbent of lead, chromates and selenites. Adsorption experiments conducted in a batch and column system demonstrated good potential for purification of water contaminated with Pb2+, Cr(VI), and Se(IV). Equilibrium adsorption capacity of EV-A in relation to Pb2+ and Cr(VI) were 48 and 54 mg g-1, respectively, while EV-B showed even better effectiveness for Se(IV) achieving 120 mg g-1 capacity. Regeneration of pollutant saturated adsorbents approved that prepared adsorbents possess fine removal potency even after five adsorption/desorption cycles from 87.58 (for Pb2+/EV-A) to 92.81 % (for Cr(VI)/EV-A) of initial adsorption capacity
The Impact of Annealing Temperatures and Chemical Assays on the Mechanical Properties and Electrical Conductivity of CuNi9Sn2
No full textThe interest in copper-based alloys with nickel and tin is constantly increasing. In this regard, certain tests were performed on CuNi9Sn2 alloy samples. In this work, the influence of annealing temperature and chemical composition on the mechanical properties and electrical conductivity of Cu-Ni9Sn2 was investigated. Tensile strength (Rm), yield strength (Rp0,2) and elongation (A) were determined in the function of annealing temperatures and content of added elements (Li and B) at a constant deformation degree