1. Stabilizacija superoksid dismutaze (sod) iz pleurotus ostreatusLuna Kuselj, 2025, magistrsko delo Opis: Magistrsko delo obravnava stabilizacijo encima superoksid dismutaze (SOD), izoliranega iz Pleurotus ostreatus, užitne gobe z odličnimi antioksidativnimi lastnostmi. Glavni namen raziskave je bil proučiti metode sproščanja intracelularnih encimov iz micelija P. ostreatus, nato pa razviti sistem enkapsulacije izolirane SOD za njeno stabilizacijo. Celice P. ostreatus smo odprli z uporabo dveh različnih metod: s konvencionalno metodo mehanske homogenizacije z rotor-stator homogenizatorjem in z izpostavitvijo superkritičnemu ogljikovemu dioksidu (SC CO2). Učinkovitost celične lize smo ovrednotili z Bradfordovo metodo, s katero smo določili koncentracijo sproščenih intracelularnih encimov, nato pa še z modificirano Marklundovo metodo, s katero smo določili aktivnost izolirane SOD. Encimski ekstrakt smo nato enkapsulirali v alginatne kroglice, ki smo jih izpostavili simulirani želodčni (SGF) in simulirani črevesni tekočini (SIF), da bi in vitro proučili sproščanje SOD v telo. Za karakterizacijo površinskih in strukturnih lastnosti ter kemijske sestave alginatnih kroglic smo uporabili vrstični elektronski mikroskop z emisijsko disperzijsko spektroskopijo (SEM-EDS). Prisotnost funkcionalnih skupin v alginatnih kroglicah smo določili s Fourierjevo transformacijsko infrardečo spektroskopijo (FTIR).
Rezultati so pokazali, da je mehanska homogenizacija pri lizi celičnih sten bolj učinkovita. Z njo smo dosegli sprostitev 4,07 mg proteinov na g P. ostreatus, medtem ko s SC CO2 le 0,0629 mg proteinov na g P. ostreatus. Specifična aktivnost SOD je bila pri obeh metodah primerljiva. Natrijev alginat se je izkazal kot odlično enkapsulacijsko sredstvo, ki vzdrži pH pogoje želodca in omogoči postopno sproščanje aktivne SOD v tankem črevesju, kar je ključnega pomena za potencialno peroralno aplikacijo. V SGF se je zaradi kislih pogojev sproščena SOD takoj deaktivirala, medtem ko je bila v SIF najvišja specifična aktivnost SOD dosežena po 180 min izpostavitve. Tedaj je za mehansko homogeniziran vzorec znašala 86,2 % začetne specifične aktivnosti enkapsuliranega vzorca, za SC CO2 vzorec pa 91,4 %. Na podlagi dobljenih rezultatov smo zaključili, da odpiranje celic z mehansko homogenizacijo in enkapsulacija v alginat nudita obetavno strategijo za kontrolirano dostavo encima SOD v tarčna področja znotraj prebavnega trakta.
Ključne besede: Pleurotus ostreatus, antioksidativni stres, superoksid dismutaza, enkapsulacija, alginatne kroglice
Objavljeno v DKUM: 20.11.2025; Ogledov: 0; Prenosov: 3
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2. Magnetna rastlinska nanoceluloza za učinkovito odstranjevanje onesnaževal : diplomsko delo visokošolskega strokovnega študijskega programa I. stopnjeTajda Gajić, 2025, diplomsko delo Opis: Onesnaževanje okolja z težkimi kovinami predstavlja vse večji globalni problem, saj se z naraščajočo industrializacije in urbanizacije njihova koncentracija v okolju povečuje. Zaradi njihove visoke toksičnosti v že zelo majhnih koncentracijah imajo negativne vplive na ljudi in okolje. Med različnimi metodami je se adsorpcija izkazala kot ena izmed najučinkovitejših, najpreprostejših in cenovno ugodnih tehnik. Kot absorbent se vse pogosteje uporabljajo biorazgradljivi polimeri, saj predstavljajo okolju prijazno in trajnostno alternativo v primerjavi z tradicionalnimi adsorbenti. V diplomskem delu smo se osredotočali predvsem na magnetno nanocelulozo, kot adsorbent za odstranjevanje kromovih ionov raztopine Kr2Cr2O7.
Cilj diplomske naloge je bil izolirati nanocelulozni material iz praproti Polypodiophyta. Uspešno sintetizirali magnetno nanocelulozo s pomočjo železovih Fe(II) in Fe(III) ionov. Pripravljeni materialsmo nato uporabili pri odstranjevnaju kromovih ionov katero smo v nadaljevanju uporabili za odstranjevanje Cr(VI) ionov iz vodne raztopine.
Določevali smo optimalne pogoje za največjo učinkovitost adsorpcije kromovih ionov, pri čemer smo se osredotočali na pH raztopine, koncentracijo kromovih ionov v vodni raztopini. Morfološke značilnosti adsorbenta pred in po adsorpciji smo analizirali z SEM analizo, TGA/DSC analizo in FTIR spektroskopijo. Za opis mehanizma adsorpcijskih procesov pa smo uporabili Freundlichovo in Langmuierjevo metodo.
Rezultati so pokazali, da se kromovi ioni najboljše adsorbirajo v kislem mediju, saj je bil največji učinek adsorpcije dosežen pri pH v vrednosti 5, saj je dosegel kar 98,84 % učinkovitost adsorpcije. Določevanje vpliva masne koncentracije medija, smo prišli do ugotovitev, da večje število prostih mest na površini adsorbenta omogoča hitrejšo adsorpcijo kromovih ionov. V našem primeru je največji učinek adsorpcije dosegel pri koncentraciji 1,00 g/mL.
Ključne besede: magnetna nanoceluloza, krom, adsorpcija, težke kovine
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3. Functionalized micellar membranes from medicinal mushrooms as promising self-growing bioscaffoldsNika Kučuk, Mateja Primožič, Željko Knez, Maja Leitgeb, 2025, izvirni znanstveni članek Opis: Micellar or mycelial membranes from medicinal mushrooms are self-growing fibrous polymeric biocomposites that are biocompatible, biodegradable, cost-effective, and environmentally friendly. In this study, the cultivation process for the medicinal mushrooms Ganoderma lucidum and Pleurotus ostreatus has been optimized via submerged cultivation to maximize growth and promote the formation of micellar membranes with high water-absorption capacity. Optimal growth conditions were achieved at an alkaline pH in a medium containing malt extract for G. lucidum, while for P. ostreatus, these were in a glucose-enriched medium. The hydrophilic underside of the micellar membranes led to a high-water uptake capacity. These membranes exhibited a broad spectrum of functional groups, thermal stability with decomposition temperatures above 260 °C, and a fibrous and porous structure. The micellar membranes from both mushrooms were additionally functionalized with mango peel extract (MPE), resulting in a uniform and gradual release profile, which is an important novelty. They also showed successful antimicrobial activity against Escherichia coli and Staphylococcus aureus growth. MPE-functionalized micellar membranes are, therefore, innovative biocomposites suitable for various biomedical applications. As they mimic the extracellular matrix of the skin, they are a promising material for tissue engineering, wound healing, and advanced skin materials applications.
Ključne besede: medicinal mushrooms, Ganoderma lucidum, Pleurotus ostreatus
Objavljeno v DKUM: 04.09.2025; Ogledov: 0; Prenosov: 4
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4. Synergistic effect of supercritical and ultrasound-assisted ginger (Zingiber officinale Roscoe) extractsTaja Žitek Makoter, Nika Kučuk, Vesna Postružnik, Maja Leitgeb, Željko Knez, Mateja Primožič, Maša Knez Marevci, 2022, izvirni znanstveni članek Opis: Proper processing of natural material is crucial to obtain an extract with high content of
biologically active components. Dried, grinded ginger roots were extracted by ultrasonic method
and supercritical extraction with CO2
. The aim of the study was to determine if a mixture of the two
types of extracts attained by different methods and solvents exhibits better bioavailability than each
extract itself. Therefore, both extracts were analytically evaluated and then mixed in a ratio of 1:1.
The supercritical extract (SCG extract) and the mixed extract (mixG extract) had high antioxidant
activity (78% and 73%) and total phenols (827 mg/g ext. and 1455 mg/g ext.), which is also consistent
with the levels of gingerol (303 mg/g ext. and 271 g/g ext.) and shogaol (111 mg/g ext. and 100 g/g
ext.) in the extracts. In comparison to both pure extracts higher levels of total phenols were found
in the extract mixG. This could be the reason for the significant inhibition of melanoma cells and
antimicrobial potential (against Staphylococcus aureus, Escherichia coli, and Candida albicans). The
combination of the extracts resulted in a significant increase in the inhibition of selected microbial
and melanoma cells WM-266-4 compared to the control. Cell viability decreased below 60% when
mixG extract was applied. Antimicrobial activity has been confirmed.
Ključne besede: ginger, supercritical fluid extraction, ultrasound-assisted extraction, antimicrobial activity
Objavljeno v DKUM: 09.05.2025; Ogledov: 0; Prenosov: 12
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5. Magnetne lastnosti magnetnih nanodelcev (MNPs) z različnimi polimernimi prevlekami : magistrsko deloKarmen Zorič, 2025, magistrsko delo Opis: Nanodelci imajo čedalje večji potencial v različnih industrijah zaradi svojih izjemnih fizikalnih in kemijskih lastnosti. Prilagajanje magnetnih lastnosti nanodelcev je ključno za oblikovanje novih večnamenskih materialov.
V magistrskem delu smo proučevali vpliv različnih razmerij ionov Fe2+ in Fe3+ na strukturne in magnetne lastnosti nanodelcev. MNPs smo sintetizirali z metodo koprecipitacije. Izvedli smo tudi študijo vpliva različnih polimernih prevlek (aminosilan ali arabinogalaktan) na lastnosti modificiranih MNPs. Prevleka preprečuje aglomeracijo MNPs in stabilizira MNPs. MNPs, prevlečeni s polimernimi prevlekami, so po navadi tudi bolj biokompatibilni.
Sintetizirane delce smo okarakterizirali z analiznimi metodami, kot so FTIR, TGA in VSM.
Z analizami smo potrdili prisotnost polimernih prevlek na površini MNPs. Določili smo termične stabilnosti modificiranih MNPs. Prav tako so vsi modificirani MNPs izkazovali superparamagnetno naravo. MNPs z arabinogalaktansko prevleko v razmerju Fe²⁺ : Fe³⁺ = 2 : 1 celo izkazujejo protibakterijsko učinkovitost na E. coli in S. aureus.
Ključne besede: magnetni nanodelci, polimerne prevleke
Objavljeno v DKUM: 07.05.2025; Ogledov: 0; Prenosov: 32
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6. Izolacija encimov in proteinov iz celic črne kvasovke Wallemia Ichthyophaga z uporabo mehanskega postopka : diplomsko delo visokošolskega strokovnega študijskega programa I. stopnjeMarko Kresnik, 2025, diplomsko delo Opis: V svetu s hitro naraščajočo populacijo, onesnaženostjo in z izčrpanjem številnih naravnih virov, encimska tehnologija ponuja velik potencial za številne industrijske aplikacije. Nekatera področja, kjer se uporablja encimska tehnologija, so prehrambena industrija (encimi se uporabljajo za izboljšanje proizvodnje hrane, na primer pri predelavi žit, proizvodnji sladkorja, sira, sokov..), farmacevtska industrija (encimi se uporabljajo v sintezi zdravil, proizvodnji antibiotikov in pripravi cepiv), tekstilna industrija, proizvodnja biogoriv, kozmetična industrija in še druge panoge. Mikrobni encimi lahko na ekonomičen in okolju prijazen način delujejo kot biokatalizatorji za izvajanje reakcij v bioprocesih. Vsak živ organizem vsebuje biološko aktivne snovi, ki jih je mogoče ekstrahirati. Mikrobne celice proizvajajo intracelularne in ekstracelularne encime. Za sprostitev intracelularnih komponent iz celice je potrebno celično steno mikrobov razbiti. Za to smo uporabili postopek mehanske homogenizacije. Postopek homogeniziranja se običajno izvaja s pomočjo homogenizacijskih naprav, ki lahko delujejo s hidravličnim tlakom, ultrazvokom, visokim tlakom ali drugimi mehanskimi silami. V našem primeru bomo uporabili rotor-stator homogenizator, kjer vzorec potuje skozi ozek prostor med vrtečim rotorjem in statorjem, kar povzroči razbijanje delcev in razlitje celic v celično suspenzijo. Namen te diplomske naloge je bil ugotoviti kako čas homogenizacije vpliva na preživelost črnih kvasovk W.Ichthyophaga v celični suspenziji, preostalo aktivnost encimov (amilaza, β- glukozidaza, proteaza, celulaza) in preostalo koncentracijo proteinov. Celično suspenzijo smo homogenizirali v času od 0 – 90 min pri konstantni temperaturi 35 ºC. Rezultati so pokazali, da je preživelost W.Ichthyophaga s podaljševanjem časa homogenizacije upadala, preostala koncentracija proteinov pa je naraščala. Zaznali smo povečanje preostale aktivnosti encimov α-amilaze, celulaze in proteaze. Na preostalo aktivnost β-glukozidaze pa je imela homogenizacija negativen vpliv, saj smo dokazali takojšen upad preostale aktivnosti.
Ključne besede: W.Ichthyophaga, črne glive, homogenizacija, encimi, proteini.
Objavljeno v DKUM: 06.05.2025; Ogledov: 0; Prenosov: 36
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7. Effect of green food processing technology on the enzyme activity in spelt flourMaja Leitgeb, Željko Knez, Gordana Hojnik Podrepšek, 2022, izvirni znanstveni članek Opis: In this research, a new approach to enzyme inactivation in flour was presented by supercritical
technology, considered a sustainable technology with lower energy consumption compared
to other technologies that use ultra-high temperature processing. Total protein concentration and
the activity of enzymes α-amylase, lipase, peroxidase, polyphenol oxidase, and protease were determined
in flour pre-treated with scCO2. During the study, it was observed that the activity of enzymes
such as lipase and polyphenol oxidase, was significantly reduced under certain conditions of scCO2
treatment, while the enzymes α-amylase and protease show better stability. In particular, polyphenol
oxidase was effectively inactivated below the 60% of preserved activity at 200 bar and 3 h, whereas
α-amylase under the same conditions retained its activity. Additionally, the moisture content of the
scCO2-treated spelt flour was reduced by 5%, and the fat content was reduced by 58%, while the
quality of scCO2-treated flour was maintained. In this regard, the sustainable scCO2 process could be
a valuable tool for controlling the enzymatic activity of spelt flour since the use of scCO2 technology
has a positive effect on the quality of flour, which was verified by the baking performance of spelt
flour with the baked spelt bread as an indicator of quality.
Ključne besede: food treatment, spelt flour, proteins, supercritical carbon dioxide, enzyme inactivation, defatted flour, carbon dioxide solubility
Objavljeno v DKUM: 17.04.2025; Ogledov: 0; Prenosov: 4
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8. Enzyme activity and physiochemical properties of flour after supercritical carbon dioxide processingMaja Leitgeb, Željko Knez, Gordana Hojnik Podrepšek, 2022, izvirni znanstveni članek 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: 5
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9. Supercritical fluid and conventional extractions of high value-added compounds from pomegranate peels waste: production, quantification and antimicrobial activity of bioactive constituentsKaja Kupnik, Maja Leitgeb, Mateja Primožič, Vesna Postružnik, Petra Kotnik, Nika Kučuk, Željko Knez, Maša Knez Marevci, 2022, izvirni znanstveni članek Opis: This study is focused on different extractions (Cold Maceration (CM), Ultrasonic Extraction
(UE), Soxhlet Extraction (SE) and Supercritical Fluid Extraction (SFE)) of bioactive compounds from
pomegranate (Punica Granatum L.) fruit peels using methanol, ethanol, and acetone as solvents in
conventional extractions and changing operating pressure (10, 15, 20, 25 MPa) in SFE, respectively.
The extraction yields, total phenols (TP) and proanthocyanidins (PAC) contents, and antioxidant
activity of different extracts are revealed. TP and PAC recovered by extracts ranged from 24.22 to
42.92 mg gallic acid equivalents (GAE)/g and 2.01 to 5.82 mg PAC/g, respectively. The antioxidant
activity of extracts ranged from 84.70% to 94.35%. The phenolic compound identification and
quantification in selective extracts was done using the LC-MS/MS method. The contents of different
flavonoids and phenolic acids have been determined. SFE extract, obtained at 20 MPa, contained
the highest content (11,561.84 µg/g) of analyzed total polyphenols, with predominant ellagic acid
(7492.53 µg/g). For the first time, Microbial Growth Inhibition Rates (MGIRs) were determined at
five different concentrations of pomegranate SFE extract against seven microorganisms. Minimal
Inhibitory Concentration (MIC90) was determined as 2.7 mg/mL of SFE pomegranate peel extract in
the case of five different Gram-negative and Gram-positive bacteria.
Ključne besede: antimicrobial activity, antioxidants, bioactive compounds, extraction, LC-MS/MS, phenolics, phytochemistry, pomegranate, Punica Granatum L., secondary metabolites
Objavljeno v DKUM: 24.03.2025; Ogledov: 0; Prenosov: 14
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10. Isolation and characterization of nanocellulose from Polypodiophyta fern using chemo-mechanical methodKatja Vasić, Monika Dokl, Željko Knez, Maja Leitgeb, 2024, izvirni znanstveni članek Opis: Nanocellulose is considered a promising and sustainable biomaterial, with excellent properties of biorenewability with improved mechanical properties. As a unique natural biopolymer, it has been applied to many different industries, where efficient and environmentally friendly productions are in demand. For the first time, ferns from the class Polypodiopsida were used for the isolation of cellulose fibers, which was performed using a chemo-mechanical method. As chemical treatment plays a crucial role in the isolation of nanocellulose, it affects the efficiency of the extraction process, as well as the properties of the resulting nanocellulose. Therefore, mechanical fibrillation was performed via grinding, while the chemical process consisted of three different treatments: alkali treatment, bleaching, and acid hydrolysis. In three different experiments, each treatment was separately prolonged to investigate the differing properties of isolated nanocellulose. Structural analysis and morphological analysis were investigated by SEM, EDS, FT-IR, and DLS. The thermal stability of cellulose fibers was investigated by TGA/DSC. The morphology of obtained nanocellulose was confirmed via SEM analysis for all samples, with particles ranging from 20 nm up to 600 nm, while the most consistent sizes were observed for NC3, ranging from 20 to 60 nm. FT-IR spectra showed prominent absorption peaks corresponding to cellulose, as well as the absence of absorption peaks, corresponding to lignin and hemicellulose. The EDS confirmed the elemental purity of nanocellulose, while TGA/DSC indicated higher thermal stability of nanocellulose, compared to untreated fern, which started to degrade earlier than nanocellulose. Such characteristics with unique properties make nanocellulose a versatile biomaterial for the industrial production of cellulosic materials.
Ključne besede: nanocellulose, isolation, Polypodiophyta fern, chemo-mechanical method, biomaterial, biopolymers
Objavljeno v DKUM: 31.01.2025; Ogledov: 0; Prenosov: 10
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