1. Genetic diversity of exopolysaccharides from acetic acid bacteria isolates originating from apple cider vinegarsTadeja Vajdič, 2022, original scientific article Abstract: Acetic acid bacteria (AAB) produce acetic acid but are also gaining importance as safe microorganisms for producing extracellular polysaccharides (EPSs). The best-known homopolysaccharides among them are cellulose and levan. In addition, acetic acid bacteria also produce heteropolysaccharides, water-soluble acetans. Isolates from the broth of organic and conventional
apple cider vinegar production were screened for biofilm production. Phenotypic and genomic
diversity of EPS-producing isolates was assessed. The diversity of phenotypically different EPSs
of apple cider vinegar isolates was investigated at the gene level for the following novel strains:
Komagataeibacter (K.) melomenusus SI3083, K. oboediens SI3053, K. pomaceti SI3133, and
Gluconacetobacter (Ga.) entanii SI2084. Strain K. melomenusus SI3083 possesses cellulose
operons bcs1, bcs2, and bcs4 together with the type I acetan cluster in the absence of the levan
operon, strain K. oboediens SI3053 has the operons bcs1, bcs2, bcs3, and bcs4, the levan operon,
and the acetan cluster (type I), and the strains K. pomaceti SI3133 and Ga. entanii SI2084
both contain recently described novel ace-type II cluster in addition to the incomplete operon
bcs1. A comparison of the genetic diversity of these EPSs to those of the reference strains suggests that the studied EPSs are not species-descriptive. The results of this study deepen our
understanding of the genetic variability of the EPS genes in AAB, thereby enabling us to better
characterize and exploit the various insoluble and soluble exopolysaccharides produced by AAB
for biotechnological applications in the future.
Keywords: acetic acid bacteria genomes, apple cider vinegar microbiota, biofilm production, bacterial cellulose, acetan, Acetobacter, Komagataeibacter
Published in DKUM: 26.09.2024; Views: 0; Downloads: 8
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2. Decomposition and fragmentation of conventional and biobased plastic wastes in simulated and real aquatic systemsOlivija Plohl, Lidija Fras Zemljič, Alen Erjavec, Noemi Sep, Maja Čolnik, Yee Van Fan, Mojca Škerget, Annamaria Vujanović, Lidija Čuček, Julija Volmajer Valh, 2024, original scientific article Abstract: Plastics play a crucial role in our daily lives. The challenge, however, is that they become waste and contribute to a global environmental problem, increasing concerns about pollution and the urgent need to protect the environment. The accumulation and fragmentation of plastic waste, especially micro- and nanoplastics in aquatic systems, poses a significant threat to ecosystems and human health. In this study, the decomposition and fragmentation processes of conventional and biobased plastic waste in simulated water bodies (waters with different pH values) and in real water systems (tap water and seawater) are investigated over a period of one and six months. Three types of plastic were examined: thermoplastic polyethylene terephthalate and thermoset melamine etherified resin in the form of nonwovens and biobased polylactic acid (PLA) in the form of foils. Such a comprehensive study involving these three types of plastics and the methodology for tracking degradation in water bodies has not been conducted before, which underlines the novelty of the present work. After aging of the plastics, both the solid fraction and the leachate in the liquid phase were carefully examined. The parameters studied include mass loss, structural changes and alterations in functional groups observed in the aged plastics. Post-exposure assessment of the fragmented pieces includes quantification of the microplastic, microscopic observations and confirmation of composition by in situ Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy. The leachate analysis includes pH, conductivity, turbidity, total carbon and microplastic size distribution. The results highlight the importance of plastic waste morphology and the minor degradation of biobased PLA and show that microfibers contribute to increased fragmentation in all aquatic systems and leave a significant ecological footprint. This study underlines the crucial importance of post-consumer plastic waste management and provides valuable insights into strategies for environmental protection. It also addresses the pressing issue of plastic pollution and provides evidence-based measures to mitigate its environmental impact.
Keywords: polylactic acid, polyethylene terephthalate fabric, melamine etherifed resin fabric, aquatic environment, fragmentation, waste disposal
Published in DKUM: 09.09.2024; Views: 73; Downloads: 7
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3. Modelling of dysregulated glucagon secretion in type 2 diabetes by considering mitochondrial alterations in pancreatic ▫$\alpha$▫-cellsVladimir Grubelnik, Rene Markovič, Saška Lipovšek Delakorda, Gerd Leitinger, Marko Gosak, Jurij Dolenšek, Ismael Valladolid-Acebes, Per-Olof Berggren, Andraž Stožer, Matjaž Perc, Marko Marhl, 2020, original scientific article Abstract: Type 2 diabetes mellitus (T2DM) has been associated with insulin resistance and the failure of β-cells to produce and secrete enough insulin as the disease progresses. However, clinical treatments based solely on insulin secretion and action have had limited success. The focus is therefore shifting towards α-cells, in particular to the dysregulated secretion of glucagon. Our qualitative electron-microscopy-based observations gave an indication that mitochondria in α-cells are altered in Western-diet-induced T2DM. In particular, α-cells extracted from mouse pancreatic tissue showed a lower density of mitochondria, a less expressed matrix and a lower number of
cristae. These deformities in mitochondrial ultrastructure imply a decreased efficiency in mitochondrial ATP production, which prompted us to theoretically explore and clarify one of the most challenging problems associated with T2DM, namely the lack of glucagon secretion in hypoglycaemia and its oversecretion at high blood glucose concentrations. To this purpose, we constructed a novel computational model that links α-cell metabolism with their electrical activity and glucagon secretion. Our results show that defective mitochondrial metabolism in α-cells can
account for dysregulated glucagon secretion in T2DM, thus improving our understanding of T2DM pathophysiology and indicating possibilities for new clinical treatments.
Keywords: diabetes, pancreatic alpha cells, glucagon, mitochondrial dysfunction, free fatty acid
Published in DKUM: 03.09.2024; Views: 49; Downloads: 4
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4. A monocarbonyl curcuminoid derivative inhibits the activity of human glutathione transferase A4-4 and chemosensitizes glioblastoma cells to temozolomideSteliana Tsouri, Evanthia Tselo, Georgios E. Premetis, Veronika Furlan, Panagiota D. Pantiora, Barbara Mavroidi, Dimitris Matiadis, Maria Pelecanou, Anastassios C. Papageorgiou, Urban Bren, Marina Sagnou, Nikolaos E. Labrou, 2024, original scientific article Keywords: chemosensitization, chemoresistance, curcumin, glioblastoma, human glutathione transferase A4-4, ellagic acid, monocarbonyl curcumin derivatives, GST inhibition, temozolomide sensitization
Published in DKUM: 23.08.2024; Views: 66; Downloads: 2
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5. Antioxidant activity of elderberry fruits during maturationNataša Imenšek, Janja Kristl, Tadeja Kraner Šumenjak, Anton Ivančič, 2021, original scientific article Abstract: Antioxidant activity (AOA) in fruits of Sambucus nigra and several new elderberry interspecific hybrids involving S. javanica (JA), S. nigra subsp. nigra (NI), S. nigra subsp. nigra ‘Black Beauty’ (BB), S. nigra subsp. cerulea (CER) and S. racemosa (S. racemosa subsp. racemosa (RAC), S. racemosa subsp. racemosa var. miquelii (MIQ), S. racemosa subsp. tigranii (TIG), S. racemosa subsp. kamtschatica—coreana (KOR) at five maturity stages were investigated by applying DPPH (2,2-diphenyl-1-picrylhydrazyl), ABTS (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)), FRAP (ferric reducing antioxidant power) and ORAC (oxygen radical absorption capacity) assays. The aim of the study was to compare different assays for estimating AOA in elderberries, to plan the appropriate harvest time and to determine whether the most promising genotypes could be predicted in advance. All assays used showed that AOA increased significantly during maturation. All assays were significantly correlated with each other and could be reliably used for the AOA determination of elderberries. In fully mature berries, significant correlations were also found between total phenolic (TP) content and AOA by all assays, but no significant correlations were found between total ascorbic acid (TAA) content and AOA by all assays. At the fully mature stage, (the most appropriate stage for harvesting), berries of (JA × NI) × BB and (JA × NI) × MIQ were found to be superior in AOA and TP content. Genotypes with higher/lower AOA and TP content could not be predicted in advance, while TAA showed the opposite.
Keywords: Sambucus, interspecific hybrids, maturation, ABTS, DPPH, ORAC, FRAP, total phenolic content, ascorbic acid, correlations
Published in DKUM: 20.08.2024; Views: 80; Downloads: 4
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6. Thermal study of APTES-functionalized magnetite nanoparticles with citric acid and polyacrylic acid for advanced forward osmosis systemsMatjaž Kristl, Urška Ostroško, Irena Ban, Irena Petrinić, Janja Stergar, 2024, original scientific article Abstract: Iron-based magnetic nanoparticles (MNPs) have attracted considerable attention as promising draw solutes in forward osmosis processes due to various advantages. In the present study, magnetite (Fe3O4) nanoparticles (MNPs) with diameters in the range of 12±2 nm were synthesized by applying the coprecipitation method and stabilized using (3-aminopropyl) triethoxysilane (APTES). The amino groups of APTES were further functionalized with various amounts of citric acid (CA) and poly(acrylic acid) (PAA) to achieve higher osmotic pressure. The as-prepared and functionalized nanoparticles were characterized using diferent methods: Fourier-transform infrared spectroscopy (FTIR) confrmed the binding of APTES and CA/PAA on the surface of the MNPs, while the size of the particles was determined by transmission electron microscopy (TEM) and X-ray powder difraction. The isoelectric point, zeta potential, and the particle size in suspension were determined by dynamic light scattering (DLS)/zeta potential measuring system. The amount of free –COOH groups was determined by conductometric titrations. The amount of organic matter (APTES, CA, and PAA) bound on the surface was determined by thermogravimetric analysis (TG), giving results between 7.6% for samples stabilized with APTES only and 17.5% for samples functionalized with APTES+PAA. TG provides a simple and efcient method for determining the amount of organic compounds bound to the surface of MNPs. The osmotic pressure measurements of double-layer coated MNPs provided encouraging results of up to 28 bar, enabling using the samples as draw solutions in an experimental forward osmosis system.
Keywords: magnetic nanoparticles, magnetite, citrit acid, poly(acrylic acid), forward osmosis
Published in DKUM: 14.08.2024; Views: 105; Downloads: 4
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7. Covalent modification of chitosan surfaces with a sugar amino acid and lysine analoguesTobias Dorn, Matjaž Finšgar, Karin Stana-Kleinschek, Tobias Alexander Steindorfer, Martin Simon Thonhofer, Tanja Wrodnigg, Rupert Kargl, 2024, original scientific article Abstract: This work explores the modifcation and characterization of chitosan thin flms as a model for functionalized polysaccharide
interfaces. The solid–liquid interface of oligo- and polysaccharides is crucial for various biological processes such as cell
adhesion and recognition. By covalent surface modifcation of the chitosan via amide formation with diferent small molecules containing carboxylic acids, e.g. specially designed glycoside hydrolase inhibitors, interactions with biomolecules and
living cells could potentially be controlled in the future. As a frst step towards this aim, three fuorescent compounds were
conjugated onto nanometric chitosan thin flms. The layers were analysed by fuorescence spectroscopy, X-ray photoelectron
spectroscopy, time-of-fight secondary ion mass spectrometry, and atomic force microscopy, to proof the covalent attachment
of the target molecules. By this analysis, a uniform and chemically stable covalent attachment of the target molecules on
the chitosan thin flms could be demonstrated under various conditions. This publication serves as a proof-of-concept-study
for further biofunctionalization, pattering, and interaction studies involving polysaccharide interfaces, glycosidase inhibitors, proteins, or living cells.
Keywords: carbohydrates, fluorescence spectroscopy, amino acid, chitosan, thin flm modifcation, C-Glycosides
Published in DKUM: 07.08.2024; Views: 127; Downloads: 6
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8. Production efficiency and properties of bacterial cellulose membranes in a novel grape pomace hydrolysate by Komagataeibacter melomenusus ▫$AV436^T$▫ and Komagataeibacter xylinus LMG 1518Selestina Gorgieva, Urška Jančič, Eva Cepec, Janja Trček, 2023, original scientific article Abstract: The microbial production of cellulose using different bacterial species has been extensively examined for various
industrial applications. However, the cost-effectiveness of all these biotechnological processes is strongly related to the culture medium for bacterial cellulose (BC) production. Herein, we examined a simple and modified
procedure for preparing grape pomace (GP) hydrolysate, without enzymatic treatment, as a sole growth medium
for BC production by acetic acid bacteria (AAB). The central composite design (CCD) was used to optimise the GP
hydrolysate preparation toward the highest reducing sugar contents (10.4 g/L) and minimal phenolic contents
(4.8 g/L). The experimental screening of 4 differently prepared hydrolysates and 20 AAB strains identified the
recently described species Komagataeibacter melomenusus AV436T as the most efficient BC producer (up to 1.24 g/
L dry BC membrane), followed by Komagataeibacter xylinus LMG 1518 (up to 0.98 g/L dry BC membrane). The
membranes were synthesized in only 4 days of bacteria culturing, 1 st day with shaking, followed by 3 days of
static incubation. The produced BC membranes in GP-hydrolysates showed, in comparison to the membranes
made in a complex RAE medium 34 % reduction of crystallinity index with the presence of diverse cellulose
allomorphs, presence of GP-related components within the BC network responsible for the increase of hydrophobicity, the reduction of thermal stability and 48.75 %, 13.6 % and 43 % lower tensile strength, tensile
modulus, and elongation, respectively. Here presented study is the first report on utilising a GP-hydrolysate
without enzymatic treatment as a sole culture medium for efficient BC production by AAB, with recently
described species Komagataeibacter melomenusus AV436T as the most efficient producer in this type of food-waste
material. The scale-up protocol of the scheme presented here will be needed for the cost-optimisation of BC
production at the industrial levels.
Keywords: grape pomace hydrolysate, bacterial cellulose, acetic acid bacteria, Komagataeibacter melomenusus
Published in DKUM: 26.07.2024; Views: 98; Downloads: 7
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9. Sustainable varroa mite (Varroa destructor) control in field conditionsAleš Gregorc, Ivo Planinc, 2022, original scientific article Abstract: Experiments assessed the comparative efficacy of oxalic acid solution (OA) and combination of formic acid (FA) evaporation and trickling OA to control the honey bee mite, Varroa destructor, at two apiary locations. Queen caging, consecutive OA treatments of broodless colonies, or combined treatments using OA and FA in colonies with brood increased mite mortality (P < 0.05) in comparison to the pre-treatment period. FA application in colonies with brood in September and October resulted in an average mite mortality of 18% in the first apiary and subsequent FA applications in the same period in the second apiary killed, on average, 73% and 71% of mites; respectively. OA treatment of broodless colonies after queen caging at two apiaries resulted in 18% and 47% mite mortality. Caging the queens and OA treatments in broodless colonies or subsequently use consecutive OA or FA treatments ensure adequate mite reduction before wintering the colonies. Synergistic control methods of Varroa mites using OA and FA along with queen caging is discussed.
Keywords: beekeeping, mite control, oxalic acid, formic acid, queen caging
Published in DKUM: 10.07.2024; Views: 107; Downloads: 4
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10. Modeling the amino acid effect on glucagon secretion from pancreatic alpha cellsJan Zmazek, Vladimir Grubelnik, Rene Markovič, Marko Marhl, 2022, original scientific article Abstract: Type 2 Diabetes Mellitus (T2DM) is a burdensome problem in modern society, and intensive research is focused on better understanding the underlying cellular mechanisms of hormone secretion for blood glucose regulation. T2DM is a bi-hormonal disease, and in addition to 100 years of increasing knowledge about the importance of insulin, the second hormone glucagon, secreted by pancreatic alpha cells, is becoming increasingly important. We have developed a mathematical model for glucagon secretion that incorporates all major metabolic processes of glucose, fatty acids, and glutamine as the most abundant postprandial amino acid in blood. In addition, we consider cAMP signaling in alpha cells. The model predictions quantitatively estimate the relative importance of specific metabolic and signaling pathways and particularly emphasize the important role of glutamine in promoting glucagon secretion, which is in good agreement with known experimental data.
Keywords: diabetes, hormone secretion, glucose, amino acid, cAMP
Published in DKUM: 21.05.2024; Views: 169; Downloads: 9
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