Iskanje po katalogu digitalne knjižnice

Opis: The objectives of this study were to inactivate the enzymes α-amylase, lipase, protease, and peroxidase in flour with supercritical carbon dioxide (scCO2), and to optimize the enzymatic treatment conditions. Enzyme inactivation is important, due to the undesirability of certain flour enzymes that cause adverse reactions during storage as unpleasant rancidity of flour, and, at the same time, reduce the shelf life of flour. Therefore, crude enzymes and flour were initially exposed to scCO2 to determine the effect on specific enzyme activity under appropriate conditions. The activity of the unwanted enzymes lipase and peroxidase decreased under optimal process conditions of scCO2 exposure, lipase by 30%, and peroxidase by 12%, respectively. It was discovered that the inactivation of enzymes in wheat flour occurred, where, at the same time, this sustainable method allows the regulation of enzyme activity in the baking process. Afterwards, the effect of scCO2 on the physicochemical properties of flour, morphological changes on starch granules, and content of total lipids was studied. In scCO2-treated white wheat flour, the fat content decreased by 46.15 ± 0.5%, the grain structure was not damaged, and the bread as the final product had a lower specific surface volume. Therefore, this could be a promising technology for flour pretreatment, potentially impacting the prolonging of its shelf-life.
Ključne besede: enzymes, enzyme activity, proteins, supercritical fluids, wheat flour
Objavljeno v DKUM: 10.04.2025; Ogledov: 0; Prenosov: 1
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Opis: The present work represents a profound investigation of material pretreatment, comparison of different isolation methods (conventional and supercritical), and characterization of phenolic compounds and amino acids from bee pollen. The determination of amino acids was carried out after developing a novel hydrophilic interaction chromatography combined with quadrupole time-of-flight tandem mass spectrometric method (HILIC-QTOF-MS/MS) with limits of detection over the range 1 mg/kg -5 mg/kg and recoveries over the range 87.6% - 97.1%. The optimal conditions for the isolation of amino acids are in the range of temperatures between 25°C to 55°C and at pressures between 300 bar and 350 bar. It can be concluded that the extraction temperature and the pressure affect antioxidant activity. The favored conditions are lower temperatures and higher pressures.
Ključne besede: bee pollen, in vitro antioxidant activity, HILIC-LC-QTOF-MS.MS, amino acids, WM-266-4 cells
Objavljeno v DKUM: 20.03.2025; Ogledov: 0; Prenosov: 2
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Opis: In this study, a novel biodegradable poly(lactic-co-glycolic) acid coating containing a model anti-inflammatory drug (ketoprofen) was prepared on TiAl6V4 substrate for use in orthopedic medicine by a two-step process combining drop casting and supercritical CO2-assisted foaming. The prepared coating was first investigated by surface analysis techniques using time-of-flight secondary ion mass spectrometry and X-ray photoelectron spectroscopy. The combined results confirmed the loading of ketoprofen and its homogeneous spatial distribution in the coating. 3D profilometry revealed increased surface roughness of the coating compared to the bare TiAl6V4 substrate, which is favorable for cell adhesion. Furthermore, the electrochemical measurements (i.e., electrochemical impedance spectroscopy and potentiodynamic curve measurements) demonstrated that the coating application significantly mitigated corrosion compared to the bare TiAl6V4 substrate. In vitro drug release tests revealed extended drug release in simulated body fluids with zero-order release kinetics. Finally, the promising cell testing results using adipose-derived mesenchymal stem cells and osteoblasts confirmed the applicability of the coating for implants. Overall, the results of this study highlight the significant potential of the developed bioactive coating for future orthopedic applications.
Ključne besede: TiAlV, bioactive coating, implants, PLGA, supercritical foaming, ketoprofen
Objavljeno v DKUM: 14.03.2025; Ogledov: 0; Prenosov: 4
Celotno besedilo (4,80 MB)

Opis: Bakterija Streptomyces clavuligerus med fermentacijskim procesom sintetizira klavulansko kislino (KK), ki učinkovito deluje kot inhibitor β-laktamaz in se uporablja v kombinaciji z antibiotiki za premagovanje bakterijske odpornosti. Nestabilnost KK med proizvodnim procesom predstavlja velik izziv, saj hitro razpada, kar zmanjšuje izkoristek in povečuje stroške proizvodnje. Namen te študije je izboljšati biosintezo KK z osredotočanjem na preučevanje vpliva procesnih parametrov na njeno stabilnost in produkcijo. V magistrskem delu smo razvili kvantitativni spektrometrični model za merjenje koncentracij KK in glicerola. Razvit model omogoča hitro, učinkovito in robustno analizo teh dveh spojin med eksperimentalnimi poskusi, kar predstavlja izboljšanje v primerjavi s klasičnimi kromatografskimi tehnikami, saj pospeši pridobivanje rezultatov. Model smo nato uporabili za spremljanje koncentracij KKin glicerola med eksperimentalnimi poskusi, v katerih smo spreminjali različne procesne parametre, kot so mešanje, zračenje, nadtlak, temperatura, redčenje ter kombinirali brozge iz različnih faz produkcijskega cikla S. clavuligerus. Poleg tega smo merili tudi koncentracijo raztopljenega kisika, viskoznost, pH in prisotnost nečistoče A, ki je razgradni produkt klavulanske kisline. Rezultati so pokazali, da lahko pravilna nastavitev procesnih parametrov bistveno izboljša stabilnost in produktivnost klavulanske kisline. Povečanje zračenja in mešanja ter zvišanje tlaka je prineslo do 5 % izboljšanje izkoristka po 6 urah zadrževalnega časa ter 17 % izboljšanje izkoristka po 27 urah procesa, hkrati pa je koncentracija nečistoče A ostala stabilna, kar kaže na manjšo razgradnjo KK. Posamezno povečanje mešanja, zračenja ali tlaka ni dalo enako učinkovitih rezultatov, čeprav je prispevalo k zmanjšanju razgradnje KK od 11 % do 26 %. Ugotovitve prispevajo k optimizaciji industrijskega procesa proizvodnje KK, saj zmanjšujejo razgradnjo produkta in povečujejo izkoristek, kar vodi v bolj učinkovit proces in nižje stroške proizvodnje.
Ključne besede: klavulanska kislina, fermentacijski proces, stabilnost, optimizacija procesnih parametrov, spektrometrija
Objavljeno v DKUM: 28.02.2025; Ogledov: 0; Prenosov: 16
Celotno besedilo (5,04 MB)

Opis: Over the past century, numerous methods for assessing cell viability have been developed, and there are many different ways to categorize these methods accordingly. We have chosen to use the Organisation for Economic Co-operation and Development (OECD) classification due to its regulatory importance. The OECD categorizes these methods into four groups: non-invasive cell structure damage, invasive cell structure damage, cell growth, and cellular metabolism. Despite the variety of cell viability methods available, they can all be categorized within these four groups, except for two novel methods based on the cell membrane potential, which we added to the list. Each method operates on different principles and has its own advantages and disadvantages, making it essential for researchers to choose the method that best fits their experimental design. This review aims to assist researchers in making this decision by describing these methods regarding their potential use and providing direct references to the cell viability assessment methods. Additionally, we use the OECD classification to facilitate potential regulatory use and to highlight the need for adding a new category to their list.
Ključne besede: cell viability, cell-based methods, in vitro toxicology, OECD cell viability classification
Objavljeno v DKUM: 13.02.2025; Ogledov: 0; Prenosov: 6
Celotno besedilo (2,77 MB)
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